FreeBSD/Linux Kernel Cross Reference
sys/include/linux/fs.h

     #ifndef _LINUX_FS_H
     #define _LINUX_FS_H
     
     
     #include <linux/linkage.h>
     #include <linux/wait.h>
     #include <linux/kdev_t.h>
     #include <linux/dcache.h>
     #include <linux/path.h>
    #include <linux/stat.h>
    #include <linux/cache.h>
    #include <linux/list.h>
    #include <linux/radix-tree.h>
    #include <linux/rbtree.h>
    #include <linux/init.h>
    #include <linux/pid.h>
    #include <linux/bug.h>
    #include <linux/mutex.h>
    #include <linux/capability.h>
    #include <linux/semaphore.h>
    #include <linux/fiemap.h>
    #include <linux/rculist_bl.h>
    #include <linux/atomic.h>
    #include <linux/shrinker.h>
    #include <linux/migrate_mode.h>
    #include <linux/uidgid.h>
    #include <linux/lockdep.h>
    #include <linux/percpu-rwsem.h>
    #include <linux/blk_types.h>
    
    #include <asm/byteorder.h>
    #include <uapi/linux/fs.h>
    
    struct export_operations;
    struct hd_geometry;
    struct iovec;
    struct nameidata;
    struct kiocb;
    struct kobject;
    struct pipe_inode_info;
    struct poll_table_struct;
    struct kstatfs;
    struct vm_area_struct;
    struct vfsmount;
    struct cred;
    struct swap_info_struct;
    struct seq_file;
    
    extern void __init inode_init(void);
    extern void __init inode_init_early(void);
    extern void __init files_init(unsigned long);
    
    extern struct files_stat_struct files_stat;
    extern unsigned long get_max_files(void);
    extern int sysctl_nr_open;
    extern struct inodes_stat_t inodes_stat;
    extern int leases_enable, lease_break_time;
    extern int sysctl_protected_symlinks;
    extern int sysctl_protected_hardlinks;
    
    struct buffer_head;
    typedef int (get_block_t)(struct inode *inode, sector_t iblock,
                            struct buffer_head *bh_result, int create);
    typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
                            ssize_t bytes, void *private, int ret,
                            bool is_async);
    
    #define MAY_EXEC                0x00000001
    #define MAY_WRITE               0x00000002
    #define MAY_READ                0x00000004
    #define MAY_APPEND              0x00000008
    #define MAY_ACCESS              0x00000010
    #define MAY_OPEN                0x00000020
    #define MAY_CHDIR               0x00000040
    /* called from RCU mode, don't block */
    #define MAY_NOT_BLOCK           0x00000080
    
    /*
     * flags in file.f_mode.  Note that FMODE_READ and FMODE_WRITE must correspond
     * to O_WRONLY and O_RDWR via the strange trick in __dentry_open()
     */
    
    /* file is open for reading */
    #define FMODE_READ              ((__force fmode_t)0x1)
    /* file is open for writing */
    #define FMODE_WRITE             ((__force fmode_t)0x2)
    /* file is seekable */
    #define FMODE_LSEEK             ((__force fmode_t)0x4)
    /* file can be accessed using pread */
    #define FMODE_PREAD             ((__force fmode_t)0x8)
    /* file can be accessed using pwrite */
    #define FMODE_PWRITE            ((__force fmode_t)0x10)
    /* File is opened for execution with sys_execve / sys_uselib */
    #define FMODE_EXEC              ((__force fmode_t)0x20)
    /* File is opened with O_NDELAY (only set for block devices) */
    #define FMODE_NDELAY            ((__force fmode_t)0x40)
    /* File is opened with O_EXCL (only set for block devices) */
    #define FMODE_EXCL              ((__force fmode_t)0x80)
    /* File is opened using open(.., 3, ..) and is writeable only for ioctls
      (specialy hack for floppy.c) */
   #define FMODE_WRITE_IOCTL       ((__force fmode_t)0x100)
   /* 32bit hashes as llseek() offset (for directories) */
   #define FMODE_32BITHASH         ((__force fmode_t)0x200)
   /* 64bit hashes as llseek() offset (for directories) */
   #define FMODE_64BITHASH         ((__force fmode_t)0x400)
   
   /*
    * Don't update ctime and mtime.
    *
    * Currently a special hack for the XFS open_by_handle ioctl, but we'll
    * hopefully graduate it to a proper O_CMTIME flag supported by open(2) soon.
    */
   #define FMODE_NOCMTIME          ((__force fmode_t)0x800)
   
   /* Expect random access pattern */
   #define FMODE_RANDOM            ((__force fmode_t)0x1000)
   
   /* File is huge (eg. /dev/kmem): treat loff_t as unsigned */
   #define FMODE_UNSIGNED_OFFSET   ((__force fmode_t)0x2000)
   
   /* File is opened with O_PATH; almost nothing can be done with it */
   #define FMODE_PATH              ((__force fmode_t)0x4000)
   
   /* File was opened by fanotify and shouldn't generate fanotify events */
   #define FMODE_NONOTIFY          ((__force fmode_t)0x1000000)
   
   /*
    * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector
    * that indicates that they should check the contents of the iovec are
    * valid, but not check the memory that the iovec elements
    * points too.
    */
   #define CHECK_IOVEC_ONLY -1
   
   /*
    * The below are the various read and write types that we support. Some of
    * them include behavioral modifiers that send information down to the
    * block layer and IO scheduler. Terminology:
    *
    *      The block layer uses device plugging to defer IO a little bit, in
    *      the hope that we will see more IO very shortly. This increases
    *      coalescing of adjacent IO and thus reduces the number of IOs we
    *      have to send to the device. It also allows for better queuing,
    *      if the IO isn't mergeable. If the caller is going to be waiting
    *      for the IO, then he must ensure that the device is unplugged so
    *      that the IO is dispatched to the driver.
    *
    *      All IO is handled async in Linux. This is fine for background
    *      writes, but for reads or writes that someone waits for completion
    *      on, we want to notify the block layer and IO scheduler so that they
    *      know about it. That allows them to make better scheduling
    *      decisions. So when the below references 'sync' and 'async', it
    *      is referencing this priority hint.
    *
    * With that in mind, the available types are:
    *
    * READ                 A normal read operation. Device will be plugged.
    * READ_SYNC            A synchronous read. Device is not plugged, caller can
    *                      immediately wait on this read without caring about
    *                      unplugging.
    * READA                Used for read-ahead operations. Lower priority, and the
    *                      block layer could (in theory) choose to ignore this
    *                      request if it runs into resource problems.
    * WRITE                A normal async write. Device will be plugged.
    * WRITE_SYNC           Synchronous write. Identical to WRITE, but passes down
    *                      the hint that someone will be waiting on this IO
    *                      shortly. The write equivalent of READ_SYNC.
    * WRITE_ODIRECT        Special case write for O_DIRECT only.
    * WRITE_FLUSH          Like WRITE_SYNC but with preceding cache flush.
    * WRITE_FUA            Like WRITE_SYNC but data is guaranteed to be on
    *                      non-volatile media on completion.
    * WRITE_FLUSH_FUA      Combination of WRITE_FLUSH and FUA. The IO is preceded
    *                      by a cache flush and data is guaranteed to be on
    *                      non-volatile media on completion.
    *
    */
   #define RW_MASK                 REQ_WRITE
   #define RWA_MASK                REQ_RAHEAD
   
   #define READ                    0
   #define WRITE                   RW_MASK
   #define READA                   RWA_MASK
   #define KERNEL_READ             (READ|REQ_KERNEL)
   #define KERNEL_WRITE            (WRITE|REQ_KERNEL)
   
   #define READ_SYNC               (READ | REQ_SYNC)
   #define WRITE_SYNC              (WRITE | REQ_SYNC | REQ_NOIDLE)
   #define WRITE_ODIRECT           (WRITE | REQ_SYNC)
   #define WRITE_FLUSH             (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FLUSH)
   #define WRITE_FUA               (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FUA)
   #define WRITE_FLUSH_FUA         (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FLUSH | REQ_FUA)
   
   /*
    * Attribute flags.  These should be or-ed together to figure out what
    * has been changed!
    */
   #define ATTR_MODE       (1 << 0)
   #define ATTR_UID        (1 << 1)
   #define ATTR_GID        (1 << 2)
   #define ATTR_SIZE       (1 << 3)
   #define ATTR_ATIME      (1 << 4)
   #define ATTR_MTIME      (1 << 5)
   #define ATTR_CTIME      (1 << 6)
   #define ATTR_ATIME_SET  (1 << 7)
   #define ATTR_MTIME_SET  (1 << 8)
   #define ATTR_FORCE      (1 << 9) /* Not a change, but a change it */
   #define ATTR_ATTR_FLAG  (1 << 10)
   #define ATTR_KILL_SUID  (1 << 11)
   #define ATTR_KILL_SGID  (1 << 12)
   #define ATTR_FILE       (1 << 13)
   #define ATTR_KILL_PRIV  (1 << 14)
   #define ATTR_OPEN       (1 << 15) /* Truncating from open(O_TRUNC) */
   #define ATTR_TIMES_SET  (1 << 16)
   
   /*
    * This is the Inode Attributes structure, used for notify_change().  It
    * uses the above definitions as flags, to know which values have changed.
    * Also, in this manner, a Filesystem can look at only the values it cares
    * about.  Basically, these are the attributes that the VFS layer can
    * request to change from the FS layer.
    *
    * Derek Atkins <warlord@MIT.EDU> 94-10-20
    */
   struct iattr {
           unsigned int    ia_valid;
           umode_t         ia_mode;
           kuid_t          ia_uid;
           kgid_t          ia_gid;
           loff_t          ia_size;
           struct timespec ia_atime;
           struct timespec ia_mtime;
           struct timespec ia_ctime;
   
           /*
            * Not an attribute, but an auxiliary info for filesystems wanting to
            * implement an ftruncate() like method.  NOTE: filesystem should
            * check for (ia_valid & ATTR_FILE), and not for (ia_file != NULL).
            */
           struct file     *ia_file;
   };
   
   /*
    * Includes for diskquotas.
    */
   #include <linux/quota.h>
   
   /** 
    * enum positive_aop_returns - aop return codes with specific semantics
    *
    * @AOP_WRITEPAGE_ACTIVATE: Informs the caller that page writeback has
    *                          completed, that the page is still locked, and
    *                          should be considered active.  The VM uses this hint
    *                          to return the page to the active list -- it won't
    *                          be a candidate for writeback again in the near
    *                          future.  Other callers must be careful to unlock
    *                          the page if they get this return.  Returned by
    *                          writepage(); 
    *
    * @AOP_TRUNCATED_PAGE: The AOP method that was handed a locked page has
    *                      unlocked it and the page might have been truncated.
    *                      The caller should back up to acquiring a new page and
    *                      trying again.  The aop will be taking reasonable
    *                      precautions not to livelock.  If the caller held a page
    *                      reference, it should drop it before retrying.  Returned
    *                      by readpage().
    *
    * address_space_operation functions return these large constants to indicate
    * special semantics to the caller.  These are much larger than the bytes in a
    * page to allow for functions that return the number of bytes operated on in a
    * given page.
    */
   
   enum positive_aop_returns {
           AOP_WRITEPAGE_ACTIVATE  = 0x80000,
           AOP_TRUNCATED_PAGE      = 0x80001,
   };
   
   #define AOP_FLAG_UNINTERRUPTIBLE        0x0001 /* will not do a short write */
   #define AOP_FLAG_CONT_EXPAND            0x0002 /* called from cont_expand */
   #define AOP_FLAG_NOFS                   0x0004 /* used by filesystem to direct
                                                   * helper code (eg buffer layer)
                                                   * to clear GFP_FS from alloc */
   
   /*
    * oh the beauties of C type declarations.
    */
   struct page;
   struct address_space;
   struct writeback_control;
   
   struct iov_iter {
           const struct iovec *iov;
           unsigned long nr_segs;
           size_t iov_offset;
           size_t count;
   };
   
   size_t iov_iter_copy_from_user_atomic(struct page *page,
                   struct iov_iter *i, unsigned long offset, size_t bytes);
   size_t iov_iter_copy_from_user(struct page *page,
                   struct iov_iter *i, unsigned long offset, size_t bytes);
   void iov_iter_advance(struct iov_iter *i, size_t bytes);
   int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
   size_t iov_iter_single_seg_count(struct iov_iter *i);
   
   static inline void iov_iter_init(struct iov_iter *i,
                           const struct iovec *iov, unsigned long nr_segs,
                           size_t count, size_t written)
   {
           i->iov = iov;
           i->nr_segs = nr_segs;
           i->iov_offset = 0;
           i->count = count + written;
   
           iov_iter_advance(i, written);
   }
   
   static inline size_t iov_iter_count(struct iov_iter *i)
   {
           return i->count;
   }
   
   /*
    * "descriptor" for what we're up to with a read.
    * This allows us to use the same read code yet
    * have multiple different users of the data that
    * we read from a file.
    *
    * The simplest case just copies the data to user
    * mode.
    */
   typedef struct {
           size_t written;
           size_t count;
           union {
                   char __user *buf;
                   void *data;
           } arg;
           int error;
   } read_descriptor_t;
   
   typedef int (*read_actor_t)(read_descriptor_t *, struct page *,
                   unsigned long, unsigned long);
   
   struct address_space_operations {
           int (*writepage)(struct page *page, struct writeback_control *wbc);
           int (*readpage)(struct file *, struct page *);
   
           /* Write back some dirty pages from this mapping. */
           int (*writepages)(struct address_space *, struct writeback_control *);
   
           /* Set a page dirty.  Return true if this dirtied it */
           int (*set_page_dirty)(struct page *page);
   
           int (*readpages)(struct file *filp, struct address_space *mapping,
                           struct list_head *pages, unsigned nr_pages);
   
           int (*write_begin)(struct file *, struct address_space *mapping,
                                   loff_t pos, unsigned len, unsigned flags,
                                   struct page **pagep, void **fsdata);
           int (*write_end)(struct file *, struct address_space *mapping,
                                   loff_t pos, unsigned len, unsigned copied,
                                   struct page *page, void *fsdata);
   
           /* Unfortunately this kludge is needed for FIBMAP. Don't use it */
           sector_t (*bmap)(struct address_space *, sector_t);
           void (*invalidatepage) (struct page *, unsigned long);
           int (*releasepage) (struct page *, gfp_t);
           void (*freepage)(struct page *);
           ssize_t (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
                           loff_t offset, unsigned long nr_segs);
           int (*get_xip_mem)(struct address_space *, pgoff_t, int,
                                                   void **, unsigned long *);
           /*
            * migrate the contents of a page to the specified target. If sync
            * is false, it must not block.
            */
           int (*migratepage) (struct address_space *,
                           struct page *, struct page *, enum migrate_mode);
           int (*launder_page) (struct page *);
           int (*is_partially_uptodate) (struct page *, read_descriptor_t *,
                                           unsigned long);
           int (*error_remove_page)(struct address_space *, struct page *);
   
           /* swapfile support */
           int (*swap_activate)(struct swap_info_struct *sis, struct file *file,
                                   sector_t *span);
           void (*swap_deactivate)(struct file *file);
   };
   
   extern const struct address_space_operations empty_aops;
   
   /*
    * pagecache_write_begin/pagecache_write_end must be used by general code
    * to write into the pagecache.
    */
   int pagecache_write_begin(struct file *, struct address_space *mapping,
                                   loff_t pos, unsigned len, unsigned flags,
                                   struct page **pagep, void **fsdata);
   
   int pagecache_write_end(struct file *, struct address_space *mapping,
                                   loff_t pos, unsigned len, unsigned copied,
                                   struct page *page, void *fsdata);
   
   struct backing_dev_info;
   struct address_space {
           struct inode            *host;          /* owner: inode, block_device */
           struct radix_tree_root  page_tree;      /* radix tree of all pages */
           spinlock_t              tree_lock;      /* and lock protecting it */
           unsigned int            i_mmap_writable;/* count VM_SHARED mappings */
           struct rb_root          i_mmap;         /* tree of private and shared mappings */
           struct list_head        i_mmap_nonlinear;/*list VM_NONLINEAR mappings */
           struct mutex            i_mmap_mutex;   /* protect tree, count, list */
           /* Protected by tree_lock together with the radix tree */
           unsigned long           nrpages;        /* number of total pages */
           pgoff_t                 writeback_index;/* writeback starts here */
           const struct address_space_operations *a_ops;   /* methods */
           unsigned long           flags;          /* error bits/gfp mask */
           struct backing_dev_info *backing_dev_info; /* device readahead, etc */
           spinlock_t              private_lock;   /* for use by the address_space */
           struct list_head        private_list;   /* ditto */
           void                    *private_data;  /* ditto */
   } __attribute__((aligned(sizeof(long))));
           /*
            * On most architectures that alignment is already the case; but
            * must be enforced here for CRIS, to let the least significant bit
            * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON.
            */
   struct request_queue;
   
   struct block_device {
           dev_t                   bd_dev;  /* not a kdev_t - it's a search key */
           int                     bd_openers;
           struct inode *          bd_inode;       /* will die */
           struct super_block *    bd_super;
           struct mutex            bd_mutex;       /* open/close mutex */
           struct list_head        bd_inodes;
           void *                  bd_claiming;
           void *                  bd_holder;
           int                     bd_holders;
           bool                    bd_write_holder;
   #ifdef CONFIG_SYSFS
           struct list_head        bd_holder_disks;
   #endif
           struct block_device *   bd_contains;
           unsigned                bd_block_size;
           struct hd_struct *      bd_part;
           /* number of times partitions within this device have been opened. */
           unsigned                bd_part_count;
           int                     bd_invalidated;
           struct gendisk *        bd_disk;
           struct request_queue *  bd_queue;
           struct list_head        bd_list;
           /*
            * Private data.  You must have bd_claim'ed the block_device
            * to use this.  NOTE:  bd_claim allows an owner to claim
            * the same device multiple times, the owner must take special
            * care to not mess up bd_private for that case.
            */
           unsigned long           bd_private;
   
           /* The counter of freeze processes */
           int                     bd_fsfreeze_count;
           /* Mutex for freeze */
           struct mutex            bd_fsfreeze_mutex;
   };
   
   /*
    * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
    * radix trees
    */
   #define PAGECACHE_TAG_DIRTY     0
   #define PAGECACHE_TAG_WRITEBACK 1
   #define PAGECACHE_TAG_TOWRITE   2
   
   int mapping_tagged(struct address_space *mapping, int tag);
   
   /*
    * Might pages of this file be mapped into userspace?
    */
   static inline int mapping_mapped(struct address_space *mapping)
   {
           return  !RB_EMPTY_ROOT(&mapping->i_mmap) ||
                   !list_empty(&mapping->i_mmap_nonlinear);
   }
   
   /*
    * Might pages of this file have been modified in userspace?
    * Note that i_mmap_writable counts all VM_SHARED vmas: do_mmap_pgoff
    * marks vma as VM_SHARED if it is shared, and the file was opened for
    * writing i.e. vma may be mprotected writable even if now readonly.
    */
   static inline int mapping_writably_mapped(struct address_space *mapping)
   {
           return mapping->i_mmap_writable != 0;
   }
   
   /*
    * Use sequence counter to get consistent i_size on 32-bit processors.
    */
   #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
   #include <linux/seqlock.h>
   #define __NEED_I_SIZE_ORDERED
   #define i_size_ordered_init(inode) seqcount_init(&inode->i_size_seqcount)
   #else
   #define i_size_ordered_init(inode) do { } while (0)
   #endif
   
   struct posix_acl;
   #define ACL_NOT_CACHED ((void *)(-1))
   
   #define IOP_FASTPERM    0x0001
   #define IOP_LOOKUP      0x0002
   #define IOP_NOFOLLOW    0x0004
   
   /*
    * Keep mostly read-only and often accessed (especially for
    * the RCU path lookup and 'stat' data) fields at the beginning
    * of the 'struct inode'
    */
   struct inode {
           umode_t                 i_mode;
           unsigned short          i_opflags;
           kuid_t                  i_uid;
           kgid_t                  i_gid;
           unsigned int            i_flags;
   
   #ifdef CONFIG_FS_POSIX_ACL
           struct posix_acl        *i_acl;
           struct posix_acl        *i_default_acl;
   #endif
   
           const struct inode_operations   *i_op;
           struct super_block      *i_sb;
           struct address_space    *i_mapping;
   
   #ifdef CONFIG_SECURITY
           void                    *i_security;
   #endif
   
           /* Stat data, not accessed from path walking */
           unsigned long           i_ino;
           /*
            * Filesystems may only read i_nlink directly.  They shall use the
            * following functions for modification:
            *
            *    (set|clear|inc|drop)_nlink
            *    inode_(inc|dec)_link_count
            */
           union {
                   const unsigned int i_nlink;
                   unsigned int __i_nlink;
           };
           dev_t                   i_rdev;
           loff_t                  i_size;
           struct timespec         i_atime;
           struct timespec         i_mtime;
           struct timespec         i_ctime;
           spinlock_t              i_lock; /* i_blocks, i_bytes, maybe i_size */
           unsigned short          i_bytes;
           unsigned int            i_blkbits;
           blkcnt_t                i_blocks;
   
   #ifdef __NEED_I_SIZE_ORDERED
           seqcount_t              i_size_seqcount;
   #endif
   
           /* Misc */
           unsigned long           i_state;
           struct mutex            i_mutex;
   
           unsigned long           dirtied_when;   /* jiffies of first dirtying */
   
           struct hlist_node       i_hash;
           struct list_head        i_wb_list;      /* backing dev IO list */
           struct list_head        i_lru;          /* inode LRU list */
           struct list_head        i_sb_list;
           union {
                   struct hlist_head       i_dentry;
                   struct rcu_head         i_rcu;
           };
           u64                     i_version;
           atomic_t                i_count;
           atomic_t                i_dio_count;
           atomic_t                i_writecount;
           const struct file_operations    *i_fop; /* former ->i_op->default_file_ops */
           struct file_lock        *i_flock;
           struct address_space    i_data;
   #ifdef CONFIG_QUOTA
           struct dquot            *i_dquot[MAXQUOTAS];
   #endif
           struct list_head        i_devices;
           union {
                   struct pipe_inode_info  *i_pipe;
                   struct block_device     *i_bdev;
                   struct cdev             *i_cdev;
           };
   
           __u32                   i_generation;
   
   #ifdef CONFIG_FSNOTIFY
           __u32                   i_fsnotify_mask; /* all events this inode cares about */
           struct hlist_head       i_fsnotify_marks;
   #endif
   
   #ifdef CONFIG_IMA
           atomic_t                i_readcount; /* struct files open RO */
   #endif
           void                    *i_private; /* fs or device private pointer */
   };
   
   static inline int inode_unhashed(struct inode *inode)
   {
           return hlist_unhashed(&inode->i_hash);
   }
   
   /*
    * inode->i_mutex nesting subclasses for the lock validator:
    *
    * 0: the object of the current VFS operation
    * 1: parent
    * 2: child/target
    * 3: quota file
    *
    * The locking order between these classes is
    * parent -> child -> normal -> xattr -> quota
    */
   enum inode_i_mutex_lock_class
   {
           I_MUTEX_NORMAL,
           I_MUTEX_PARENT,
           I_MUTEX_CHILD,
           I_MUTEX_XATTR,
           I_MUTEX_QUOTA
   };
   
   /*
    * NOTE: in a 32bit arch with a preemptable kernel and
    * an UP compile the i_size_read/write must be atomic
    * with respect to the local cpu (unlike with preempt disabled),
    * but they don't need to be atomic with respect to other cpus like in
    * true SMP (so they need either to either locally disable irq around
    * the read or for example on x86 they can be still implemented as a
    * cmpxchg8b without the need of the lock prefix). For SMP compiles
    * and 64bit archs it makes no difference if preempt is enabled or not.
    */
   static inline loff_t i_size_read(const struct inode *inode)
   {
   #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
           loff_t i_size;
           unsigned int seq;
   
           do {
                   seq = read_seqcount_begin(&inode->i_size_seqcount);
                   i_size = inode->i_size;
           } while (read_seqcount_retry(&inode->i_size_seqcount, seq));
           return i_size;
   #elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
           loff_t i_size;
   
           preempt_disable();
           i_size = inode->i_size;
           preempt_enable();
           return i_size;
   #else
           return inode->i_size;
   #endif
   }
   
   /*
    * NOTE: unlike i_size_read(), i_size_write() does need locking around it
    * (normally i_mutex), otherwise on 32bit/SMP an update of i_size_seqcount
    * can be lost, resulting in subsequent i_size_read() calls spinning forever.
    */
   static inline void i_size_write(struct inode *inode, loff_t i_size)
   {
   #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
           write_seqcount_begin(&inode->i_size_seqcount);
           inode->i_size = i_size;
           write_seqcount_end(&inode->i_size_seqcount);
   #elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
           preempt_disable();
           inode->i_size = i_size;
           preempt_enable();
   #else
           inode->i_size = i_size;
   #endif
   }
   
   /* Helper functions so that in most cases filesystems will
    * not need to deal directly with kuid_t and kgid_t and can
    * instead deal with the raw numeric values that are stored
    * in the filesystem.
    */
   static inline uid_t i_uid_read(const struct inode *inode)
   {
           return from_kuid(&init_user_ns, inode->i_uid);
   }
   
   static inline gid_t i_gid_read(const struct inode *inode)
   {
           return from_kgid(&init_user_ns, inode->i_gid);
   }
   
   static inline void i_uid_write(struct inode *inode, uid_t uid)
   {
           inode->i_uid = make_kuid(&init_user_ns, uid);
   }
   
   static inline void i_gid_write(struct inode *inode, gid_t gid)
   {
           inode->i_gid = make_kgid(&init_user_ns, gid);
   }
   
   static inline unsigned iminor(const struct inode *inode)
   {
           return MINOR(inode->i_rdev);
   }
   
   static inline unsigned imajor(const struct inode *inode)
   {
           return MAJOR(inode->i_rdev);
   }
   
   extern struct block_device *I_BDEV(struct inode *inode);
   
   struct fown_struct {
           rwlock_t lock;          /* protects pid, uid, euid fields */
           struct pid *pid;        /* pid or -pgrp where SIGIO should be sent */
           enum pid_type pid_type; /* Kind of process group SIGIO should be sent to */
           kuid_t uid, euid;       /* uid/euid of process setting the owner */
           int signum;             /* posix.1b rt signal to be delivered on IO */
   };
   
   /*
    * Track a single file's readahead state
    */
   struct file_ra_state {
           pgoff_t start;                  /* where readahead started */
           unsigned int size;              /* # of readahead pages */
           unsigned int async_size;        /* do asynchronous readahead when
                                              there are only # of pages ahead */
   
           unsigned int ra_pages;          /* Maximum readahead window */
           unsigned int mmap_miss;         /* Cache miss stat for mmap accesses */
           loff_t prev_pos;                /* Cache last read() position */
   };
   
   /*
    * Check if @index falls in the readahead windows.
    */
   static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
   {
           return (index >= ra->start &&
                   index <  ra->start + ra->size);
   }
   
   #define FILE_MNT_WRITE_TAKEN    1
   #define FILE_MNT_WRITE_RELEASED 2
   
   struct file {
           /*
            * fu_list becomes invalid after file_free is called and queued via
            * fu_rcuhead for RCU freeing
            */
           union {
                   struct list_head        fu_list;
                   struct rcu_head         fu_rcuhead;
           } f_u;
           struct path             f_path;
   #define f_dentry        f_path.dentry
   #define f_vfsmnt        f_path.mnt
           const struct file_operations    *f_op;
   
           /*
            * Protects f_ep_links, f_flags, f_pos vs i_size in lseek SEEK_CUR.
            * Must not be taken from IRQ context.
            */
           spinlock_t              f_lock;
   #ifdef CONFIG_SMP
           int                     f_sb_list_cpu;
   #endif
           atomic_long_t           f_count;
           unsigned int            f_flags;
           fmode_t                 f_mode;
           loff_t                  f_pos;
           struct fown_struct      f_owner;
           const struct cred       *f_cred;
           struct file_ra_state    f_ra;
   
           u64                     f_version;
   #ifdef CONFIG_SECURITY
           void                    *f_security;
   #endif
           /* needed for tty driver, and maybe others */
           void                    *private_data;
   
   #ifdef CONFIG_EPOLL
           /* Used by fs/eventpoll.c to link all the hooks to this file */
           struct list_head        f_ep_links;
           struct list_head        f_tfile_llink;
   #endif /* #ifdef CONFIG_EPOLL */
           struct address_space    *f_mapping;
   #ifdef CONFIG_DEBUG_WRITECOUNT
           unsigned long f_mnt_write_state;
   #endif
   };
   
   struct file_handle {
           __u32 handle_bytes;
           int handle_type;
           /* file identifier */
           unsigned char f_handle[0];
   };
   
   static inline struct file *get_file(struct file *f)
   {
           atomic_long_inc(&f->f_count);
           return f;
   }
   #define fput_atomic(x)  atomic_long_add_unless(&(x)->f_count, -1, 1)
   #define file_count(x)   atomic_long_read(&(x)->f_count)
   
   #ifdef CONFIG_DEBUG_WRITECOUNT
   static inline void file_take_write(struct file *f)
   {
           WARN_ON(f->f_mnt_write_state != 0);
           f->f_mnt_write_state = FILE_MNT_WRITE_TAKEN;
   }
   static inline void file_release_write(struct file *f)
   {
           f->f_mnt_write_state |= FILE_MNT_WRITE_RELEASED;
   }
   static inline void file_reset_write(struct file *f)
   {
           f->f_mnt_write_state = 0;
   }
   static inline void file_check_state(struct file *f)
   {
           /*
            * At this point, either both or neither of these bits
            * should be set.
            */
           WARN_ON(f->f_mnt_write_state == FILE_MNT_WRITE_TAKEN);
           WARN_ON(f->f_mnt_write_state == FILE_MNT_WRITE_RELEASED);
   }
   static inline int file_check_writeable(struct file *f)
   {
           if (f->f_mnt_write_state == FILE_MNT_WRITE_TAKEN)
                   return 0;
           printk(KERN_WARNING "writeable file with no "
                               "mnt_want_write()\n");
           WARN_ON(1);
           return -EINVAL;
   }
   #else /* !CONFIG_DEBUG_WRITECOUNT */
   static inline void file_take_write(struct file *filp) {}
   static inline void file_release_write(struct file *filp) {}
   static inline void file_reset_write(struct file *filp) {}
   static inline void file_check_state(struct file *filp) {}
   static inline int file_check_writeable(struct file *filp)
   {
           return 0;
   }
   #endif /* CONFIG_DEBUG_WRITECOUNT */
   
   #define MAX_NON_LFS     ((1UL<<31) - 1)
   
   /* Page cache limit. The filesystems should put that into their s_maxbytes 
      limits, otherwise bad things can happen in VM. */ 
   #if BITS_PER_LONG==32
   #define MAX_LFS_FILESIZE        (((loff_t)PAGE_CACHE_SIZE << (BITS_PER_LONG-1))-1) 
   #elif BITS_PER_LONG==64
   #define MAX_LFS_FILESIZE        ((loff_t)0x7fffffffffffffffLL)
   #endif
   
   #define FL_POSIX        1
   #define FL_FLOCK        2
   #define FL_ACCESS       8       /* not trying to lock, just looking */
   #define FL_EXISTS       16      /* when unlocking, test for existence */
   #define FL_LEASE        32      /* lease held on this file */
   #define FL_CLOSE        64      /* unlock on close */
   #define FL_SLEEP        128     /* A blocking lock */
   #define FL_DOWNGRADE_PENDING    256 /* Lease is being downgraded */
   #define FL_UNLOCK_PENDING       512 /* Lease is being broken */
   
   /*
    * Special return value from posix_lock_file() and vfs_lock_file() for
    * asynchronous locking.
    */
   #define FILE_LOCK_DEFERRED 1
   
   /*
    * The POSIX file lock owner is determined by
    * the "struct files_struct" in the thread group
    * (or NULL for no owner - BSD locks).
    *
    * Lockd stuffs a "host" pointer into this.
    */
   typedef struct files_struct *fl_owner_t;
   
   struct file_lock_operations {
           void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
           void (*fl_release_private)(struct file_lock *);
   };
   
   struct lock_manager_operations {
           int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
           void (*lm_notify)(struct file_lock *);  /* unblock callback */
           int (*lm_grant)(struct file_lock *, struct file_lock *, int);
           void (*lm_break)(struct file_lock *);
           int (*lm_change)(struct file_lock **, int);
   };
   
   struct lock_manager {
           struct list_head list;
   };
   
   struct net;
   void locks_start_grace(struct net *, struct lock_manager *);
   void locks_end_grace(struct lock_manager *);
   int locks_in_grace(struct net *);
   
   /* that will die - we need it for nfs_lock_info */
   #include <linux/nfs_fs_i.h>
   
   struct file_lock {
           struct file_lock *fl_next;      /* singly linked list for this inode  */
           struct list_head fl_link;       /* doubly linked list of all locks */
           struct list_head fl_block;      /* circular list of blocked processes */
           fl_owner_t fl_owner;
           unsigned int fl_flags;
           unsigned char fl_type;
           unsigned int fl_pid;
           struct pid *fl_nspid;
           wait_queue_head_t fl_wait;
           struct file *fl_file;
           loff_t fl_start;
           loff_t fl_end;
   
           struct fasync_struct *  fl_fasync; /* for lease break notifications */
           /* for lease breaks: */
           unsigned long fl_break_time;
           unsigned long fl_downgrade_time;
   
           const struct file_lock_operations *fl_ops;      /* Callbacks for filesystems */
           const struct lock_manager_operations *fl_lmops; /* Callbacks for lockmanagers */
           union {
                   struct nfs_lock_info    nfs_fl;
                   struct nfs4_lock_info   nfs4_fl;
                   struct {
                           struct list_head link;  /* link in AFS vnode's pending_locks list */
                           int state;              /* state of grant or error if -ve */
                   } afs;
           } fl_u;
   };
   
   /* The following constant reflects the upper bound of the file/locking space */
   #ifndef OFFSET_MAX
   #define INT_LIMIT(x)    (~((x)1 << (sizeof(x)*8 - 1)))
   #define OFFSET_MAX      INT_LIMIT(loff_t)
   #define OFFT_OFFSET_MAX INT_LIMIT(off_t)
   #endif
   
   #include <linux/fcntl.h>
   
   extern void send_sigio(struct fown_struct *fown, int fd, int band);
   
   #ifdef CONFIG_FILE_LOCKING
   extern int fcntl_getlk(struct file *, struct flock __user *);
   extern int fcntl_setlk(unsigned int, struct file *, unsigned int,
                           struct flock __user *);
   
   #if BITS_PER_LONG == 32
   extern int fcntl_getlk64(struct file *, struct flock64 __user *);
   extern int fcntl_setlk64(unsigned int, struct file *, unsigned int,
                           struct flock64 __user *);
   #endif
   
   extern int fcntl_setlease(unsigned int fd, struct file *filp, long arg);
   extern int fcntl_getlease(struct file *filp);
   
   /* fs/locks.c */
   void locks_free_lock(struct file_lock *fl);
   extern void locks_init_lock(struct file_lock *);
   extern struct file_lock * locks_alloc_lock(void);
   extern void locks_copy_lock(struct file_lock *, struct file_lock *);
   extern void __locks_copy_lock(struct file_lock *, const struct file_lock *);
   extern void locks_remove_posix(struct file *, fl_owner_t);
   extern void locks_remove_flock(struct file *);
   extern void locks_release_private(struct file_lock *);
   extern void posix_test_lock(struct file *, struct file_lock *);
   extern int posix_lock_file(struct file *, struct file_lock *, struct file_lock *);
   extern int posix_lock_file_wait(struct file *, struct file_lock *);
   extern int posix_unblock_lock(struct file *, struct file_lock *);
   extern int vfs_test_lock(struct file *, struct file_lock *);
   extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
   extern int vfs_cancel_lock(struct file *filp, struct file_lock *fl);
   extern int flock_lock_file_wait(struct file *filp, struct file_lock *fl);
  extern int __break_lease(struct inode *inode, unsigned int flags);
  extern void lease_get_mtime(struct inode *, struct timespec *time);
  extern int generic_setlease(struct file *, long, struct file_lock **);
  extern int vfs_setlease(struct file *, long, struct file_lock **);
  extern int lease_modify(struct file_lock **, int);
  extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
  extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
  extern void locks_delete_block(struct file_lock *waiter);
  extern void lock_flocks(void);
  extern void unlock_flocks(void);
  #else /* !CONFIG_FILE_LOCKING */
  static inline int fcntl_getlk(struct file *file, struct flock __user *user)
  {
          return -EINVAL;
  }
  
  static inline int fcntl_setlk(unsigned int fd, struct file *file,
                                unsigned int cmd, struct flock __user *user)
  {
          return -EACCES;
  }
  
  #if BITS_PER_LONG == 32
  static inline int fcntl_getlk64(struct file *file, struct flock64 __user *user)
  {
          return -EINVAL;
  }
  
  static inline int fcntl_setlk64(unsigned int fd, struct file *file,
                                  unsigned int cmd, struct flock64 __user *user)
  {
          return -EACCES;
  }
  #endif
  static inline int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
  {
          return 0;
  }
  
  static inline int fcntl_getlease(struct file *filp)
  {
          return 0;
  }
  
  static inline void locks_init_lock(struct file_lock *fl)
  {
          return;
  }
  
  static inline void __locks_copy_lock(struct file_lock *new, struct file_lock *fl)
  {
          return;
  }
  
  static inline void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
  {
          return;
  }
  
  static inline void locks_remove_posix(struct file *filp, fl_owner_t owner)
  {
          return;
  }
  
  static inline void locks_remove_flock(struct file *filp)
  {
          return;
  }
  
  static inline void posix_test_lock(struct file *filp, struct file_lock *fl)
  {
          return;
  }
  
  static inline int posix_lock_file(struct file *filp, struct file_lock *fl,
                                    struct file_lock *conflock)
  {
          return -ENOLCK;
  }
  
  static inline int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
  {
          return -ENOLCK;
  }
  
  static inline int posix_unblock_lock(struct file *filp,
                                       struct file_lock *waiter)
  {
          return -ENOENT;
  }
  
  static inline int vfs_test_lock(struct file *filp, struct file_lock *fl)
  {
          return 0;
  }
  
  static inline int vfs_lock_file(struct file *filp, unsigned int cmd,
                                  struct file_lock *fl, struct file_lock *conf)
  {
          return -ENOLCK;
  }
  
  static inline int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
  {
          return 0;
  }
  
  static inline int flock_lock_file_wait(struct file *filp,
                                         struct file_lock *request)
  {
          return -ENOLCK;
  }
  
  static inline int __break_lease(struct inode *inode, unsigned int mode)
  {
          return 0;
  }
  
  static inline void lease_get_mtime(struct inode *inode, struct timespec *time)
  {
          return;
  }
  
  static inline int generic_setlease(struct file *filp, long arg,
                                      struct file_lock **flp)
  {
          return -EINVAL;
  }
  
  static inline int vfs_setlease(struct file *filp, long arg,
                                 struct file_lock **lease)
  {
          return -EINVAL;
  }
  
  static inline int lease_modify(struct file_lock **before, int arg)
  {
          return -EINVAL;
  }
  
  static inline int lock_may_read(struct inode *inode, loff_t start,
                                  unsigned long len)
  {
          return 1;
  }
  
  static inline int lock_may_write(struct inode *inode, loff_t start,
                                   unsigned long len)
  {
          return 1;
  }
  
  static inline void locks_delete_block(struct file_lock *waiter)
  {
  }
  
  static inline void lock_flocks(void)
  {
  }
  
  static inline void unlock_flocks(void)
  {
  }
  
  #endif /* !CONFIG_FILE_LOCKING */
  
  
  struct fasync_struct {
          spinlock_t              fa_lock;
          int                     magic;
          int                     fa_fd;
          struct fasync_struct    *fa_next; /* singly linked list */
          struct file             *fa_file;
          struct rcu_head         fa_rcu;
  };
  
  #define FASYNC_MAGIC 0x4601
  
  /* SMP safe fasync helpers: */
  extern int fasync_helper(int, struct file *, int, struct fasync_struct **);
  extern struct fasync_struct *fasync_insert_entry(int, struct file *, struct fasync_struct **, struct fasync_struct *);
  extern int fasync_remove_entry(struct file *, struct fasync_struct **);
  extern struct fasync_struct *fasync_alloc(void);
  extern void fasync_free(struct fasync_struct *);
  
  /* can be called from interrupts */
  extern void kill_fasync(struct fasync_struct **, int, int);
  
  extern int __f_setown(struct file *filp, struct pid *, enum pid_type, int force);
  extern int f_setown(struct file *filp, unsigned long arg, int force);
  extern void f_delown(struct file *filp);
  extern pid_t f_getown(struct file *filp);
  extern int send_sigurg(struct fown_struct *fown);
  
  struct mm_struct;
  
  /*
   *      Umount options
   */
  
  #define MNT_FORCE       0x00000001      /* Attempt to forcibily umount */
  #define MNT_DETACH      0x00000002      /* Just detach from the tree */
  #define MNT_EXPIRE      0x00000004      /* Mark for expiry */
  #define UMOUNT_NOFOLLOW 0x00000008      /* Don't follow symlink on umount */
  #define UMOUNT_UNUSED   0x80000000      /* Flag guaranteed to be unused */
  
  extern struct list_head super_blocks;
  extern spinlock_t sb_lock;
  
  /* Possible states of 'frozen' field */
  enum {
          SB_UNFROZEN = 0,                /* FS is unfrozen */
          SB_FREEZE_WRITE = 1,            /* Writes, dir ops, ioctls frozen */
          SB_FREEZE_PAGEFAULT = 2,        /* Page faults stopped as well */
          SB_FREEZE_FS = 3,               /* For internal FS use (e.g. to stop
                                           * internal threads if needed) */
          SB_FREEZE_COMPLETE = 4,         /* ->freeze_fs finished successfully */
  };
  
  #define SB_FREEZE_LEVELS (SB_FREEZE_COMPLETE - 1)
  
  struct sb_writers {
          /* Counters for counting writers at each level */
          struct percpu_counter   counter[SB_FREEZE_LEVELS];
          wait_queue_head_t       wait;           /* queue for waiting for
                                                     writers / faults to finish */
          int                     frozen;         /* Is sb frozen? */
          wait_queue_head_t       wait_unfrozen;  /* queue for waiting for
                                                     sb to be thawed */
  #ifdef CONFIG_DEBUG_LOCK_ALLOC
          struct lockdep_map      lock_map[SB_FREEZE_LEVELS];
  #endif
  };
  
  struct super_block {
          struct list_head        s_list;         /* Keep this first */
          dev_t                   s_dev;          /* search index; _not_ kdev_t */
          unsigned char           s_blocksize_bits;
          unsigned long           s_blocksize;
          loff_t                  s_maxbytes;     /* Max file size */
          struct file_system_type *s_type;
          const struct super_operations   *s_op;
          const struct dquot_operations   *dq_op;
          const struct quotactl_ops       *s_qcop;
          const struct export_operations *s_export_op;
          unsigned long           s_flags;
          unsigned long           s_magic;
          struct dentry           *s_root;
          struct rw_semaphore     s_umount;
          int                     s_count;
          atomic_t                s_active;
  #ifdef CONFIG_SECURITY
          void                    *s_security;
  #endif
          const struct xattr_handler **s_xattr;
  
          struct list_head        s_inodes;       /* all inodes */
          struct hlist_bl_head    s_anon;         /* anonymous dentries for (nfs) exporting */
  #ifdef CONFIG_SMP
          struct list_head __percpu *s_files;
  #else
          struct list_head        s_files;
  #endif
          struct list_head        s_mounts;       /* list of mounts; _not_ for fs use */
          /* s_dentry_lru, s_nr_dentry_unused protected by dcache.c lru locks */
          struct list_head        s_dentry_lru;   /* unused dentry lru */
          int                     s_nr_dentry_unused;     /* # of dentry on lru */
  
          /* s_inode_lru_lock protects s_inode_lru and s_nr_inodes_unused */
          spinlock_t              s_inode_lru_lock ____cacheline_aligned_in_smp;
          struct list_head        s_inode_lru;            /* unused inode lru */
          int                     s_nr_inodes_unused;     /* # of inodes on lru */
  
          struct block_device     *s_bdev;
          struct backing_dev_info *s_bdi;
          struct mtd_info         *s_mtd;
          struct hlist_node       s_instances;
          struct quota_info       s_dquot;        /* Diskquota specific options */
  
          struct sb_writers       s_writers;
  
          char s_id[32];                          /* Informational name */
          u8 s_uuid[16];                          /* UUID */
  
          void                    *s_fs_info;     /* Filesystem private info */
          unsigned int            s_max_links;
          fmode_t                 s_mode;
  
          /* Granularity of c/m/atime in ns.
             Cannot be worse than a second */
          u32                s_time_gran;
  
          /*
           * The next field is for VFS *only*. No filesystems have any business
           * even looking at it. You had been warned.
           */
          struct mutex s_vfs_rename_mutex;        /* Kludge */
  
          /*
           * Filesystem subtype.  If non-empty the filesystem type field
           * in /proc/mounts will be "type.subtype"
           */
          char *s_subtype;
  
          /*
           * Saved mount options for lazy filesystems using
           * generic_show_options()
           */
          char __rcu *s_options;
          const struct dentry_operations *s_d_op; /* default d_op for dentries */
  
          /*
           * Saved pool identifier for cleancache (-1 means none)
           */
          int cleancache_poolid;
  
          struct shrinker s_shrink;       /* per-sb shrinker handle */
  
          /* Number of inodes with nlink == 0 but still referenced */
          atomic_long_t s_remove_count;
  
          /* Being remounted read-only */
          int s_readonly_remount;
  };
  
  /* superblock cache pruning functions */
  extern void prune_icache_sb(struct super_block *sb, int nr_to_scan);
  extern void prune_dcache_sb(struct super_block *sb, int nr_to_scan);
  
  extern struct timespec current_fs_time(struct super_block *sb);
  
  /*
   * Snapshotting support.
   */
  
  void __sb_end_write(struct super_block *sb, int level);
  int __sb_start_write(struct super_block *sb, int level, bool wait);
  
  /**
   * sb_end_write - drop write access to a superblock
   * @sb: the super we wrote to
   *
   * Decrement number of writers to the filesystem. Wake up possible waiters
   * wanting to freeze the filesystem.
   */
  static inline void sb_end_write(struct super_block *sb)
  {
          __sb_end_write(sb, SB_FREEZE_WRITE);
  }
  
  /**
   * sb_end_pagefault - drop write access to a superblock from a page fault
   * @sb: the super we wrote to
   *
   * Decrement number of processes handling write page fault to the filesystem.
   * Wake up possible waiters wanting to freeze the filesystem.
   */
  static inline void sb_end_pagefault(struct super_block *sb)
  {
          __sb_end_write(sb, SB_FREEZE_PAGEFAULT);
  }
  
  /**
   * sb_end_intwrite - drop write access to a superblock for internal fs purposes
   * @sb: the super we wrote to
   *
   * Decrement fs-internal number of writers to the filesystem.  Wake up possible
   * waiters wanting to freeze the filesystem.
   */
  static inline void sb_end_intwrite(struct super_block *sb)
  {
          __sb_end_write(sb, SB_FREEZE_FS);
  }
  
  /**
   * sb_start_write - get write access to a superblock
   * @sb: the super we write to
   *
   * When a process wants to write data or metadata to a file system (i.e. dirty
   * a page or an inode), it should embed the operation in a sb_start_write() -
   * sb_end_write() pair to get exclusion against file system freezing. This
   * function increments number of writers preventing freezing. If the file
   * system is already frozen, the function waits until the file system is
   * thawed.
   *
   * Since freeze protection behaves as a lock, users have to preserve
   * ordering of freeze protection and other filesystem locks. Generally,
   * freeze protection should be the outermost lock. In particular, we have:
   *
   * sb_start_write
   *   -> i_mutex                 (write path, truncate, directory ops, ...)
   *   -> s_umount                (freeze_super, thaw_super)
   */
  static inline void sb_start_write(struct super_block *sb)
  {
          __sb_start_write(sb, SB_FREEZE_WRITE, true);
  }
  
  static inline int sb_start_write_trylock(struct super_block *sb)
  {
          return __sb_start_write(sb, SB_FREEZE_WRITE, false);
  }
  
  /**
   * sb_start_pagefault - get write access to a superblock from a page fault
   * @sb: the super we write to
   *
   * When a process starts handling write page fault, it should embed the
   * operation into sb_start_pagefault() - sb_end_pagefault() pair to get
   * exclusion against file system freezing. This is needed since the page fault
   * is going to dirty a page. This function increments number of running page
   * faults preventing freezing. If the file system is already frozen, the
   * function waits until the file system is thawed.
   *
   * Since page fault freeze protection behaves as a lock, users have to preserve
   * ordering of freeze protection and other filesystem locks. It is advised to
   * put sb_start_pagefault() close to mmap_sem in lock ordering. Page fault
   * handling code implies lock dependency:
   *
   * mmap_sem
   *   -> sb_start_pagefault
   */
  static inline void sb_start_pagefault(struct super_block *sb)
  {
          __sb_start_write(sb, SB_FREEZE_PAGEFAULT, true);
  }
  
  /*
   * sb_start_intwrite - get write access to a superblock for internal fs purposes
   * @sb: the super we write to
   *
   * This is the third level of protection against filesystem freezing. It is
   * free for use by a filesystem. The only requirement is that it must rank
   * below sb_start_pagefault.
   *
   * For example filesystem can call sb_start_intwrite() when starting a
   * transaction which somewhat eases handling of freezing for internal sources
   * of filesystem changes (internal fs threads, discarding preallocation on file
   * close, etc.).
   */
  static inline void sb_start_intwrite(struct super_block *sb)
  {
          __sb_start_write(sb, SB_FREEZE_FS, true);
  }
  
  
  extern bool inode_owner_or_capable(const struct inode *inode);
  
  /*
   * VFS helper functions..
   */
  extern int vfs_create(struct inode *, struct dentry *, umode_t, bool);
  extern int vfs_mkdir(struct inode *, struct dentry *, umode_t);
  extern int vfs_mknod(struct inode *, struct dentry *, umode_t, dev_t);
  extern int vfs_symlink(struct inode *, struct dentry *, const char *);
  extern int vfs_link(struct dentry *, struct inode *, struct dentry *);
  extern int vfs_rmdir(struct inode *, struct dentry *);
  extern int vfs_unlink(struct inode *, struct dentry *);
  extern int vfs_rename(struct inode *, struct dentry *, struct inode *, struct dentry *);
  
  /*
   * VFS dentry helper functions.
   */
  extern void dentry_unhash(struct dentry *dentry);
  
  /*
   * VFS file helper functions.
   */
  extern void inode_init_owner(struct inode *inode, const struct inode *dir,
                          umode_t mode);
  /*
   * VFS FS_IOC_FIEMAP helper definitions.
   */
  struct fiemap_extent_info {
          unsigned int fi_flags;          /* Flags as passed from user */
          unsigned int fi_extents_mapped; /* Number of mapped extents */
          unsigned int fi_extents_max;    /* Size of fiemap_extent array */
          struct fiemap_extent __user *fi_extents_start; /* Start of
                                                          fiemap_extent array */
  };
  int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
                              u64 phys, u64 len, u32 flags);
  int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
  
  /*
   * File types
   *
   * NOTE! These match bits 12..15 of stat.st_mode
   * (ie "(i_mode >> 12) & 15").
   */
  #define DT_UNKNOWN      0
  #define DT_FIFO         1
  #define DT_CHR          2
  #define DT_DIR          4
  #define DT_BLK          6
  #define DT_REG          8
  #define DT_LNK          10
  #define DT_SOCK         12
  #define DT_WHT          14
  
  /*
   * This is the "filldir" function type, used by readdir() to let
   * the kernel specify what kind of dirent layout it wants to have.
   * This allows the kernel to read directories into kernel space or
   * to have different dirent layouts depending on the binary type.
   */
  typedef int (*filldir_t)(void *, const char *, int, loff_t, u64, unsigned);
  struct block_device_operations;
  
  /* These macros are for out of kernel modules to test that
   * the kernel supports the unlocked_ioctl and compat_ioctl
   * fields in struct file_operations. */
  #define HAVE_COMPAT_IOCTL 1
  #define HAVE_UNLOCKED_IOCTL 1
  
  struct file_operations {
          struct module *owner;
          loff_t (*llseek) (struct file *, loff_t, int);
          ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
          ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
          ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
          ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
          int (*readdir) (struct file *, void *, filldir_t);
          unsigned int (*poll) (struct file *, struct poll_table_struct *);
          long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
          long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
          int (*mmap) (struct file *, struct vm_area_struct *);
          int (*open) (struct inode *, struct file *);
          int (*flush) (struct file *, fl_owner_t id);
          int (*release) (struct inode *, struct file *);
          int (*fsync) (struct file *, loff_t, loff_t, int datasync);
          int (*aio_fsync) (struct kiocb *, int datasync);
          int (*fasync) (int, struct file *, int);
          int (*lock) (struct file *, int, struct file_lock *);
          ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
          unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
          int (*check_flags)(int);
          int (*flock) (struct file *, int, struct file_lock *);
          ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
          ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
          int (*setlease)(struct file *, long, struct file_lock **);
          long (*fallocate)(struct file *file, int mode, loff_t offset,
                            loff_t len);
          int (*show_fdinfo)(struct seq_file *m, struct file *f);
  };
  
  struct inode_operations {
          struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
          void * (*follow_link) (struct dentry *, struct nameidata *);
          int (*permission) (struct inode *, int);
          struct posix_acl * (*get_acl)(struct inode *, int);
  
          int (*readlink) (struct dentry *, char __user *,int);
          void (*put_link) (struct dentry *, struct nameidata *, void *);
  
          int (*create) (struct inode *,struct dentry *, umode_t, bool);
          int (*link) (struct dentry *,struct inode *,struct dentry *);
          int (*unlink) (struct inode *,struct dentry *);
          int (*symlink) (struct inode *,struct dentry *,const char *);
          int (*mkdir) (struct inode *,struct dentry *,umode_t);
          int (*rmdir) (struct inode *,struct dentry *);
          int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
          int (*rename) (struct inode *, struct dentry *,
                          struct inode *, struct dentry *);
          int (*setattr) (struct dentry *, struct iattr *);
          int (*getattr) (struct vfsmount *mnt, struct dentry *, struct kstat *);
          int (*setxattr) (struct dentry *, const char *,const void *,size_t,int);
          ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t);
          ssize_t (*listxattr) (struct dentry *, char *, size_t);
          int (*removexattr) (struct dentry *, const char *);
          int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
                        u64 len);
          int (*update_time)(struct inode *, struct timespec *, int);
          int (*atomic_open)(struct inode *, struct dentry *,
                             struct file *, unsigned open_flag,
                             umode_t create_mode, int *opened);
  } ____cacheline_aligned;
  
  ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
                                unsigned long nr_segs, unsigned long fast_segs,
                                struct iovec *fast_pointer,
                                struct iovec **ret_pointer);
  
  extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
  extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
  extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
                  unsigned long, loff_t *);
  extern ssize_t vfs_writev(struct file *, const struct iovec __user *,
                  unsigned long, loff_t *);
  
  struct super_operations {
          struct inode *(*alloc_inode)(struct super_block *sb);
          void (*destroy_inode)(struct inode *);
  
          void (*dirty_inode) (struct inode *, int flags);
          int (*write_inode) (struct inode *, struct writeback_control *wbc);
          int (*drop_inode) (struct inode *);
          void (*evict_inode) (struct inode *);
          void (*put_super) (struct super_block *);
          int (*sync_fs)(struct super_block *sb, int wait);
          int (*freeze_fs) (struct super_block *);
          int (*unfreeze_fs) (struct super_block *);
          int (*statfs) (struct dentry *, struct kstatfs *);
          int (*remount_fs) (struct super_block *, int *, char *);
          void (*umount_begin) (struct super_block *);
  
          int (*show_options)(struct seq_file *, struct dentry *);
          int (*show_devname)(struct seq_file *, struct dentry *);
          int (*show_path)(struct seq_file *, struct dentry *);
          int (*show_stats)(struct seq_file *, struct dentry *);
  #ifdef CONFIG_QUOTA
          ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
          ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
  #endif
          int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
          int (*nr_cached_objects)(struct super_block *);
          void (*free_cached_objects)(struct super_block *, int);
  };
  
  /*
   * Inode flags - they have no relation to superblock flags now
   */
  #define S_SYNC          1       /* Writes are synced at once */
  #define S_NOATIME       2       /* Do not update access times */
  #define S_APPEND        4       /* Append-only file */
  #define S_IMMUTABLE     8       /* Immutable file */
  #define S_DEAD          16      /* removed, but still open directory */
  #define S_NOQUOTA       32      /* Inode is not counted to quota */
  #define S_DIRSYNC       64      /* Directory modifications are synchronous */
  #define S_NOCMTIME      128     /* Do not update file c/mtime */
  #define S_SWAPFILE      256     /* Do not truncate: swapon got its bmaps */
  #define S_PRIVATE       512     /* Inode is fs-internal */
  #define S_IMA           1024    /* Inode has an associated IMA struct */
  #define S_AUTOMOUNT     2048    /* Automount/referral quasi-directory */
  #define S_NOSEC         4096    /* no suid or xattr security attributes */
  
  /*
   * Note that nosuid etc flags are inode-specific: setting some file-system
   * flags just means all the inodes inherit those flags by default. It might be
   * possible to override it selectively if you really wanted to with some
   * ioctl() that is not currently implemented.
   *
   * Exception: MS_RDONLY is always applied to the entire file system.
   *
   * Unfortunately, it is possible to change a filesystems flags with it mounted
   * with files in use.  This means that all of the inodes will not have their
   * i_flags updated.  Hence, i_flags no longer inherit the superblock mount
   * flags, so these have to be checked separately. -- rmk@arm.uk.linux.org
   */
  #define __IS_FLG(inode, flg)    ((inode)->i_sb->s_flags & (flg))
  
  #define IS_RDONLY(inode)        ((inode)->i_sb->s_flags & MS_RDONLY)
  #define IS_SYNC(inode)          (__IS_FLG(inode, MS_SYNCHRONOUS) || \
                                          ((inode)->i_flags & S_SYNC))
  #define IS_DIRSYNC(inode)       (__IS_FLG(inode, MS_SYNCHRONOUS|MS_DIRSYNC) || \
                                          ((inode)->i_flags & (S_SYNC|S_DIRSYNC)))
  #define IS_MANDLOCK(inode)      __IS_FLG(inode, MS_MANDLOCK)
  #define IS_NOATIME(inode)       __IS_FLG(inode, MS_RDONLY|MS_NOATIME)
  #define IS_I_VERSION(inode)     __IS_FLG(inode, MS_I_VERSION)
  
  #define IS_NOQUOTA(inode)       ((inode)->i_flags & S_NOQUOTA)
  #define IS_APPEND(inode)        ((inode)->i_flags & S_APPEND)
  #define IS_IMMUTABLE(inode)     ((inode)->i_flags & S_IMMUTABLE)
  #define IS_POSIXACL(inode)      __IS_FLG(inode, MS_POSIXACL)
  
  #define IS_DEADDIR(inode)       ((inode)->i_flags & S_DEAD)
  #define IS_NOCMTIME(inode)      ((inode)->i_flags & S_NOCMTIME)
  #define IS_SWAPFILE(inode)      ((inode)->i_flags & S_SWAPFILE)
  #define IS_PRIVATE(inode)       ((inode)->i_flags & S_PRIVATE)
  #define IS_IMA(inode)           ((inode)->i_flags & S_IMA)
  #define IS_AUTOMOUNT(inode)     ((inode)->i_flags & S_AUTOMOUNT)
  #define IS_NOSEC(inode)         ((inode)->i_flags & S_NOSEC)
  
  /*
   * Inode state bits.  Protected by inode->i_lock
   *
   * Three bits determine the dirty state of the inode, I_DIRTY_SYNC,
   * I_DIRTY_DATASYNC and I_DIRTY_PAGES.
   *
   * Four bits define the lifetime of an inode.  Initially, inodes are I_NEW,
   * until that flag is cleared.  I_WILL_FREE, I_FREEING and I_CLEAR are set at
   * various stages of removing an inode.
   *
   * Two bits are used for locking and completion notification, I_NEW and I_SYNC.
   *
   * I_DIRTY_SYNC         Inode is dirty, but doesn't have to be written on
   *                      fdatasync().  i_atime is the usual cause.
   * I_DIRTY_DATASYNC     Data-related inode changes pending. We keep track of
   *                      these changes separately from I_DIRTY_SYNC so that we
   *                      don't have to write inode on fdatasync() when only
   *                      mtime has changed in it.
   * I_DIRTY_PAGES        Inode has dirty pages.  Inode itself may be clean.
   * I_NEW                Serves as both a mutex and completion notification.
   *                      New inodes set I_NEW.  If two processes both create
   *                      the same inode, one of them will release its inode and
   *                      wait for I_NEW to be released before returning.
   *                      Inodes in I_WILL_FREE, I_FREEING or I_CLEAR state can
   *                      also cause waiting on I_NEW, without I_NEW actually
   *                      being set.  find_inode() uses this to prevent returning
   *                      nearly-dead inodes.
   * I_WILL_FREE          Must be set when calling write_inode_now() if i_count
   *                      is zero.  I_FREEING must be set when I_WILL_FREE is
   *                      cleared.
   * I_FREEING            Set when inode is about to be freed but still has dirty
   *                      pages or buffers attached or the inode itself is still
   *                      dirty.
   * I_CLEAR              Added by clear_inode().  In this state the inode is
   *                      clean and can be destroyed.  Inode keeps I_FREEING.
   *
   *                      Inodes that are I_WILL_FREE, I_FREEING or I_CLEAR are
   *                      prohibited for many purposes.  iget() must wait for
   *                      the inode to be completely released, then create it
   *                      anew.  Other functions will just ignore such inodes,
   *                      if appropriate.  I_NEW is used for waiting.
   *
   * I_SYNC               Writeback of inode is running. The bit is set during
   *                      data writeback, and cleared with a wakeup on the bit
   *                      address once it is done. The bit is also used to pin
   *                      the inode in memory for flusher thread.
   *
   * I_REFERENCED         Marks the inode as recently references on the LRU list.
   *
   * I_DIO_WAKEUP         Never set.  Only used as a key for wait_on_bit().
   *
   * Q: What is the difference between I_WILL_FREE and I_FREEING?
   */
  #define I_DIRTY_SYNC            (1 << 0)
  #define I_DIRTY_DATASYNC        (1 << 1)
  #define I_DIRTY_PAGES           (1 << 2)
  #define __I_NEW                 3
  #define I_NEW                   (1 << __I_NEW)
  #define I_WILL_FREE             (1 << 4)
  #define I_FREEING               (1 << 5)
  #define I_CLEAR                 (1 << 6)
  #define __I_SYNC                7
  #define I_SYNC                  (1 << __I_SYNC)
  #define I_REFERENCED            (1 << 8)
  #define __I_DIO_WAKEUP          9
  #define I_DIO_WAKEUP            (1 << I_DIO_WAKEUP)
  
  #define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES)
  
  extern void __mark_inode_dirty(struct inode *, int);
  static inline void mark_inode_dirty(struct inode *inode)
  {
          __mark_inode_dirty(inode, I_DIRTY);
  }
  
  static inline void mark_inode_dirty_sync(struct inode *inode)
  {
          __mark_inode_dirty(inode, I_DIRTY_SYNC);
  }
  
  extern void inc_nlink(struct inode *inode);
  extern void drop_nlink(struct inode *inode);
  extern void clear_nlink(struct inode *inode);
  extern void set_nlink(struct inode *inode, unsigned int nlink);
  
  static inline void inode_inc_link_count(struct inode *inode)
  {
          inc_nlink(inode);
          mark_inode_dirty(inode);
  }
  
  static inline void inode_dec_link_count(struct inode *inode)
  {
          drop_nlink(inode);
          mark_inode_dirty(inode);
  }
  
  /**
   * inode_inc_iversion - increments i_version
   * @inode: inode that need to be updated
   *
   * Every time the inode is modified, the i_version field will be incremented.
   * The filesystem has to be mounted with i_version flag
   */
  
  static inline void inode_inc_iversion(struct inode *inode)
  {
         spin_lock(&inode->i_lock);
         inode->i_version++;
         spin_unlock(&inode->i_lock);
  }
  
  enum file_time_flags {
          S_ATIME = 1,
          S_MTIME = 2,
          S_CTIME = 4,
          S_VERSION = 8,
  };
  
  extern void touch_atime(struct path *);
  static inline void file_accessed(struct file *file)
  {
          if (!(file->f_flags & O_NOATIME))
                  touch_atime(&file->f_path);
  }
  
  int sync_inode(struct inode *inode, struct writeback_control *wbc);
  int sync_inode_metadata(struct inode *inode, int wait);
  
  struct file_system_type {
          const char *name;
          int fs_flags;
  #define FS_REQUIRES_DEV         1 
  #define FS_BINARY_MOUNTDATA     2
  #define FS_HAS_SUBTYPE          4
  #define FS_USERNS_MOUNT         8       /* Can be mounted by userns root */
  #define FS_USERNS_DEV_MOUNT     16 /* A userns mount does not imply MNT_NODEV */
  #define FS_REVAL_DOT            16384   /* Check the paths ".", ".." for staleness */
  #define FS_RENAME_DOES_D_MOVE   32768   /* FS will handle d_move() during rename() internally. */
          struct dentry *(*mount) (struct file_system_type *, int,
                         const char *, void *);
          void (*kill_sb) (struct super_block *);
          struct module *owner;
          struct file_system_type * next;
          struct hlist_head fs_supers;
  
          struct lock_class_key s_lock_key;
          struct lock_class_key s_umount_key;
          struct lock_class_key s_vfs_rename_key;
          struct lock_class_key s_writers_key[SB_FREEZE_LEVELS];
  
          struct lock_class_key i_lock_key;
          struct lock_class_key i_mutex_key;
          struct lock_class_key i_mutex_dir_key;
  };
  
  extern struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
          void *data, int (*fill_super)(struct super_block *, void *, int));
  extern struct dentry *mount_bdev(struct file_system_type *fs_type,
          int flags, const char *dev_name, void *data,
          int (*fill_super)(struct super_block *, void *, int));
  extern struct dentry *mount_single(struct file_system_type *fs_type,
          int flags, void *data,
          int (*fill_super)(struct super_block *, void *, int));
  extern struct dentry *mount_nodev(struct file_system_type *fs_type,
          int flags, void *data,
          int (*fill_super)(struct super_block *, void *, int));
  extern struct dentry *mount_subtree(struct vfsmount *mnt, const char *path);
  void generic_shutdown_super(struct super_block *sb);
  void kill_block_super(struct super_block *sb);
  void kill_anon_super(struct super_block *sb);
  void kill_litter_super(struct super_block *sb);
  void deactivate_super(struct super_block *sb);
  void deactivate_locked_super(struct super_block *sb);
  int set_anon_super(struct super_block *s, void *data);
  int get_anon_bdev(dev_t *);
  void free_anon_bdev(dev_t);
  struct super_block *sget(struct file_system_type *type,
                          int (*test)(struct super_block *,void *),
                          int (*set)(struct super_block *,void *),
                          int flags, void *data);
  extern struct dentry *mount_pseudo(struct file_system_type *, char *,
          const struct super_operations *ops,
          const struct dentry_operations *dops,
          unsigned long);
  
  /* Alas, no aliases. Too much hassle with bringing module.h everywhere */
  #define fops_get(fops) \
          (((fops) && try_module_get((fops)->owner) ? (fops) : NULL))
  #define fops_put(fops) \
          do { if (fops) module_put((fops)->owner); } while(0)
  
  extern int register_filesystem(struct file_system_type *);
  extern int unregister_filesystem(struct file_system_type *);
  extern struct vfsmount *kern_mount_data(struct file_system_type *, void *data);
  #define kern_mount(type) kern_mount_data(type, NULL)
  extern void kern_unmount(struct vfsmount *mnt);
  extern int may_umount_tree(struct vfsmount *);
  extern int may_umount(struct vfsmount *);
  extern long do_mount(const char *, const char *, const char *, unsigned long, void *);
  extern struct vfsmount *collect_mounts(struct path *);
  extern void drop_collected_mounts(struct vfsmount *);
  extern int iterate_mounts(int (*)(struct vfsmount *, void *), void *,
                            struct vfsmount *);
  extern int vfs_statfs(struct path *, struct kstatfs *);
  extern int user_statfs(const char __user *, struct kstatfs *);
  extern int fd_statfs(int, struct kstatfs *);
  extern int vfs_ustat(dev_t, struct kstatfs *);
  extern int freeze_super(struct super_block *super);
  extern int thaw_super(struct super_block *super);
  extern bool our_mnt(struct vfsmount *mnt);
  
  extern int current_umask(void);
  
  /* /sys/fs */
  extern struct kobject *fs_kobj;
  
  #define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK)
  extern int rw_verify_area(int, struct file *, loff_t *, size_t);
  
  #define FLOCK_VERIFY_READ  1
  #define FLOCK_VERIFY_WRITE 2
  
  #ifdef CONFIG_FILE_LOCKING
  extern int locks_mandatory_locked(struct inode *);
  extern int locks_mandatory_area(int, struct inode *, struct file *, loff_t, size_t);
  
  /*
   * Candidates for mandatory locking have the setgid bit set
   * but no group execute bit -  an otherwise meaningless combination.
   */
  
  static inline int __mandatory_lock(struct inode *ino)
  {
          return (ino->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID;
  }
  
  /*
   * ... and these candidates should be on MS_MANDLOCK mounted fs,
   * otherwise these will be advisory locks
   */
  
  static inline int mandatory_lock(struct inode *ino)
  {
          return IS_MANDLOCK(ino) && __mandatory_lock(ino);
  }
  
  static inline int locks_verify_locked(struct inode *inode)
  {
          if (mandatory_lock(inode))
                  return locks_mandatory_locked(inode);
          return 0;
  }
  
  static inline int locks_verify_truncate(struct inode *inode,
                                      struct file *filp,
                                      loff_t size)
  {
          if (inode->i_flock && mandatory_lock(inode))
                  return locks_mandatory_area(
                          FLOCK_VERIFY_WRITE, inode, filp,
                          size < inode->i_size ? size : inode->i_size,
                          (size < inode->i_size ? inode->i_size - size
                           : size - inode->i_size)
                  );
          return 0;
  }
  
  static inline int break_lease(struct inode *inode, unsigned int mode)
  {
          if (inode->i_flock)
                  return __break_lease(inode, mode);
          return 0;
  }
  #else /* !CONFIG_FILE_LOCKING */
  static inline int locks_mandatory_locked(struct inode *inode)
  {
          return 0;
  }
  
  static inline int locks_mandatory_area(int rw, struct inode *inode,
                                         struct file *filp, loff_t offset,
                                         size_t count)
  {
          return 0;
  }
  
  static inline int __mandatory_lock(struct inode *inode)
  {
          return 0;
  }
  
  static inline int mandatory_lock(struct inode *inode)
  {
          return 0;
  }
  
  static inline int locks_verify_locked(struct inode *inode)
  {
          return 0;
  }
  
  static inline int locks_verify_truncate(struct inode *inode, struct file *filp,
                                          size_t size)
  {
          return 0;
  }
  
  static inline int break_lease(struct inode *inode, unsigned int mode)
  {
          return 0;
  }
  
  #endif /* CONFIG_FILE_LOCKING */
  
  /* fs/open.c */
  struct audit_names;
  struct filename {
          const char              *name;  /* pointer to actual string */
          const __user char       *uptr;  /* original userland pointer */
          struct audit_names      *aname;
          bool                    separate; /* should "name" be freed? */
  };
  
  extern long vfs_truncate(struct path *, loff_t);
  extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
                         struct file *filp);
  extern int do_fallocate(struct file *file, int mode, loff_t offset,
                          loff_t len);
  extern long do_sys_open(int dfd, const char __user *filename, int flags,
                          umode_t mode);
  extern struct file *file_open_name(struct filename *, int, umode_t);
  extern struct file *filp_open(const char *, int, umode_t);
  extern struct file *file_open_root(struct dentry *, struct vfsmount *,
                                     const char *, int);
  extern struct file * dentry_open(const struct path *, int, const struct cred *);
  extern int filp_close(struct file *, fl_owner_t id);
  
  extern struct filename *getname(const char __user *);
  
  enum {
          FILE_CREATED = 1,
          FILE_OPENED = 2
  };
  extern int finish_open(struct file *file, struct dentry *dentry,
                          int (*open)(struct inode *, struct file *),
                          int *opened);
  extern int finish_no_open(struct file *file, struct dentry *dentry);
  
  /* fs/ioctl.c */
  
  extern int ioctl_preallocate(struct file *filp, void __user *argp);
  
  /* fs/dcache.c */
  extern void __init vfs_caches_init_early(void);
  extern void __init vfs_caches_init(unsigned long);
  
  extern struct kmem_cache *names_cachep;
  
  extern void final_putname(struct filename *name);
  
  #define __getname()             kmem_cache_alloc(names_cachep, GFP_KERNEL)
  #define __putname(name)         kmem_cache_free(names_cachep, (void *)(name))
  #ifndef CONFIG_AUDITSYSCALL
  #define putname(name)           final_putname(name)
  #else
  extern void putname(struct filename *name);
  #endif
  
  #ifdef CONFIG_BLOCK
  extern int register_blkdev(unsigned int, const char *);
  extern void unregister_blkdev(unsigned int, const char *);
  extern struct block_device *bdget(dev_t);
  extern struct block_device *bdgrab(struct block_device *bdev);
  extern void bd_set_size(struct block_device *, loff_t size);
  extern void bd_forget(struct inode *inode);
  extern void bdput(struct block_device *);
  extern void invalidate_bdev(struct block_device *);
  extern void iterate_bdevs(void (*)(struct block_device *, void *), void *);
  extern int sync_blockdev(struct block_device *bdev);
  extern void kill_bdev(struct block_device *);
  extern struct super_block *freeze_bdev(struct block_device *);
  extern void emergency_thaw_all(void);
  extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
  extern int fsync_bdev(struct block_device *);
  #else
  static inline void bd_forget(struct inode *inode) {}
  static inline int sync_blockdev(struct block_device *bdev) { return 0; }
  static inline void kill_bdev(struct block_device *bdev) {}
  static inline void invalidate_bdev(struct block_device *bdev) {}
  
  static inline struct super_block *freeze_bdev(struct block_device *sb)
  {
          return NULL;
  }
  
  static inline int thaw_bdev(struct block_device *bdev, struct super_block *sb)
  {
          return 0;
  }
  
  static inline void iterate_bdevs(void (*f)(struct block_device *, void *), void *arg)
  {
  }
  #endif
  extern int sync_filesystem(struct super_block *);
  extern const struct file_operations def_blk_fops;
  extern const struct file_operations def_chr_fops;
  extern const struct file_operations bad_sock_fops;
  extern const struct file_operations def_fifo_fops;
  #ifdef CONFIG_BLOCK
  extern int ioctl_by_bdev(struct block_device *, unsigned, unsigned long);
  extern int blkdev_ioctl(struct block_device *, fmode_t, unsigned, unsigned long);
  extern long compat_blkdev_ioctl(struct file *, unsigned, unsigned long);
  extern int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder);
  extern struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
                                                 void *holder);
  extern struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode,
                                                void *holder);
  extern int blkdev_put(struct block_device *bdev, fmode_t mode);
  #ifdef CONFIG_SYSFS
  extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
  extern void bd_unlink_disk_holder(struct block_device *bdev,
                                    struct gendisk *disk);
  #else
  static inline int bd_link_disk_holder(struct block_device *bdev,
                                        struct gendisk *disk)
  {
          return 0;
  }
  static inline void bd_unlink_disk_holder(struct block_device *bdev,
                                           struct gendisk *disk)
  {
  }
  #endif
  #endif
  
  /* fs/char_dev.c */
  #define CHRDEV_MAJOR_HASH_SIZE  255
  extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *);
  extern int register_chrdev_region(dev_t, unsigned, const char *);
  extern int __register_chrdev(unsigned int major, unsigned int baseminor,
                               unsigned int count, const char *name,
                               const struct file_operations *fops);
  extern void __unregister_chrdev(unsigned int major, unsigned int baseminor,
                                  unsigned int count, const char *name);
  extern void unregister_chrdev_region(dev_t, unsigned);
  extern void chrdev_show(struct seq_file *,off_t);
  
  static inline int register_chrdev(unsigned int major, const char *name,
                                    const struct file_operations *fops)
  {
          return __register_chrdev(major, 0, 256, name, fops);
  }
  
  static inline void unregister_chrdev(unsigned int major, const char *name)
  {
          __unregister_chrdev(major, 0, 256, name);
  }
  
  /* fs/block_dev.c */
  #define BDEVNAME_SIZE   32      /* Largest string for a blockdev identifier */
  #define BDEVT_SIZE      10      /* Largest string for MAJ:MIN for blkdev */
  
  #ifdef CONFIG_BLOCK
  #define BLKDEV_MAJOR_HASH_SIZE  255
  extern const char *__bdevname(dev_t, char *buffer);
  extern const char *bdevname(struct block_device *bdev, char *buffer);
  extern struct block_device *lookup_bdev(const char *);
  extern void blkdev_show(struct seq_file *,off_t);
  
  #else
  #define BLKDEV_MAJOR_HASH_SIZE  0
  #endif
  
  extern void init_special_inode(struct inode *, umode_t, dev_t);
  
  /* Invalid inode operations -- fs/bad_inode.c */
  extern void make_bad_inode(struct inode *);
  extern int is_bad_inode(struct inode *);
  
  extern const struct file_operations read_pipefifo_fops;
  extern const struct file_operations write_pipefifo_fops;
  extern const struct file_operations rdwr_pipefifo_fops;
  
  #ifdef CONFIG_BLOCK
  /*
   * return READ, READA, or WRITE
   */
  #define bio_rw(bio)             ((bio)->bi_rw & (RW_MASK | RWA_MASK))
  
  /*
   * return data direction, READ or WRITE
   */
  #define bio_data_dir(bio)       ((bio)->bi_rw & 1)
  
  extern void check_disk_size_change(struct gendisk *disk,
                                     struct block_device *bdev);
  extern int revalidate_disk(struct gendisk *);
  extern int check_disk_change(struct block_device *);
  extern int __invalidate_device(struct block_device *, bool);
  extern int invalidate_partition(struct gendisk *, int);
  #endif
  unsigned long invalidate_mapping_pages(struct address_space *mapping,
                                          pgoff_t start, pgoff_t end);
  
  static inline void invalidate_remote_inode(struct inode *inode)
  {
          if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
              S_ISLNK(inode->i_mode))
                  invalidate_mapping_pages(inode->i_mapping, 0, -1);
  }
  extern int invalidate_inode_pages2(struct address_space *mapping);
  extern int invalidate_inode_pages2_range(struct address_space *mapping,
                                           pgoff_t start, pgoff_t end);
  extern int write_inode_now(struct inode *, int);
  extern int filemap_fdatawrite(struct address_space *);
  extern int filemap_flush(struct address_space *);
  extern int filemap_fdatawait(struct address_space *);
  extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
                                     loff_t lend);
  extern int filemap_write_and_wait(struct address_space *mapping);
  extern int filemap_write_and_wait_range(struct address_space *mapping,
                                          loff_t lstart, loff_t lend);
  extern int __filemap_fdatawrite_range(struct address_space *mapping,
                                  loff_t start, loff_t end, int sync_mode);
  extern int filemap_fdatawrite_range(struct address_space *mapping,
                                  loff_t start, loff_t end);
  
  extern int vfs_fsync_range(struct file *file, loff_t start, loff_t end,
                             int datasync);
  extern int vfs_fsync(struct file *file, int datasync);
  extern int generic_write_sync(struct file *file, loff_t pos, loff_t count);
  extern void emergency_sync(void);
  extern void emergency_remount(void);
  #ifdef CONFIG_BLOCK
  extern sector_t bmap(struct inode *, sector_t);
  #endif
  extern int notify_change(struct dentry *, struct iattr *);
  extern int inode_permission(struct inode *, int);
  extern int generic_permission(struct inode *, int);
  
  static inline bool execute_ok(struct inode *inode)
  {
          return (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode);
  }
  
  /*
   * get_write_access() gets write permission for a file.
   * put_write_access() releases this write permission.
   * This is used for regular files.
   * We cannot support write (and maybe mmap read-write shared) accesses and
   * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
   * can have the following values:
   * 0: no writers, no VM_DENYWRITE mappings
   * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
   * > 0: (i_writecount) users are writing to the file.
   *
   * Normally we operate on that counter with atomic_{inc,dec} and it's safe
   * except for the cases where we don't hold i_writecount yet. Then we need to
   * use {get,deny}_write_access() - these functions check the sign and refuse
   * to do the change if sign is wrong.
   */
  static inline int get_write_access(struct inode *inode)
  {
          return atomic_inc_unless_negative(&inode->i_writecount) ? 0 : -ETXTBSY;
  }
  static inline int deny_write_access(struct file *file)
  {
          struct inode *inode = file->f_path.dentry->d_inode;
          return atomic_dec_unless_positive(&inode->i_writecount) ? 0 : -ETXTBSY;
  }
  static inline void put_write_access(struct inode * inode)
  {
          atomic_dec(&inode->i_writecount);
  }
  static inline void allow_write_access(struct file *file)
  {
          if (file)
                  atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
  }
  #ifdef CONFIG_IMA
  static inline void i_readcount_dec(struct inode *inode)
  {
          BUG_ON(!atomic_read(&inode->i_readcount));
          atomic_dec(&inode->i_readcount);
  }
  static inline void i_readcount_inc(struct inode *inode)
  {
          atomic_inc(&inode->i_readcount);
  }
  #else
  static inline void i_readcount_dec(struct inode *inode)
  {
          return;
  }
  static inline void i_readcount_inc(struct inode *inode)
  {
          return;
  }
  #endif
  extern int do_pipe_flags(int *, int);
  
  extern int kernel_read(struct file *, loff_t, char *, unsigned long);
  extern struct file * open_exec(const char *);
   
  /* fs/dcache.c -- generic fs support functions */
  extern int is_subdir(struct dentry *, struct dentry *);
  extern int path_is_under(struct path *, struct path *);
  extern ino_t find_inode_number(struct dentry *, struct qstr *);
  
  #include <linux/err.h>
  
  /* needed for stackable file system support */
  extern loff_t default_llseek(struct file *file, loff_t offset, int whence);
  
  extern loff_t vfs_llseek(struct file *file, loff_t offset, int whence);
  
  extern int inode_init_always(struct super_block *, struct inode *);
  extern void inode_init_once(struct inode *);
  extern void address_space_init_once(struct address_space *mapping);
  extern void ihold(struct inode * inode);
  extern void iput(struct inode *);
  extern struct inode * igrab(struct inode *);
  extern ino_t iunique(struct super_block *, ino_t);
  extern int inode_needs_sync(struct inode *inode);
  extern int generic_delete_inode(struct inode *inode);
  static inline int generic_drop_inode(struct inode *inode)
  {
          return !inode->i_nlink || inode_unhashed(inode);
  }
  
  extern struct inode *ilookup5_nowait(struct super_block *sb,
                  unsigned long hashval, int (*test)(struct inode *, void *),
                  void *data);
  extern struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
                  int (*test)(struct inode *, void *), void *data);
  extern struct inode *ilookup(struct super_block *sb, unsigned long ino);
  
  extern struct inode * iget5_locked(struct super_block *, unsigned long, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *);
  extern struct inode * iget_locked(struct super_block *, unsigned long);
  extern int insert_inode_locked4(struct inode *, unsigned long, int (*test)(struct inode *, void *), void *);
  extern int insert_inode_locked(struct inode *);
  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  extern void lockdep_annotate_inode_mutex_key(struct inode *inode);
  #else
  static inline void lockdep_annotate_inode_mutex_key(struct inode *inode) { };
  #endif
  extern void unlock_new_inode(struct inode *);
  extern unsigned int get_next_ino(void);
  
  extern void __iget(struct inode * inode);
  extern void iget_failed(struct inode *);
  extern void clear_inode(struct inode *);
  extern void __destroy_inode(struct inode *);
  extern struct inode *new_inode_pseudo(struct super_block *sb);
  extern struct inode *new_inode(struct super_block *sb);
  extern void free_inode_nonrcu(struct inode *inode);
  extern int should_remove_suid(struct dentry *);
  extern int file_remove_suid(struct file *);
  
  extern void __insert_inode_hash(struct inode *, unsigned long hashval);
  static inline void insert_inode_hash(struct inode *inode)
  {
          __insert_inode_hash(inode, inode->i_ino);
  }
  
  extern void __remove_inode_hash(struct inode *);
  static inline void remove_inode_hash(struct inode *inode)
  {
          if (!inode_unhashed(inode))
                  __remove_inode_hash(inode);
  }
  
  extern void inode_sb_list_add(struct inode *inode);
  
  #ifdef CONFIG_BLOCK
  extern void submit_bio(int, struct bio *);
  extern int bdev_read_only(struct block_device *);
  #endif
  extern int set_blocksize(struct block_device *, int);
  extern int sb_set_blocksize(struct super_block *, int);
  extern int sb_min_blocksize(struct super_block *, int);
  
  extern int generic_file_mmap(struct file *, struct vm_area_struct *);
  extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
  extern int generic_file_remap_pages(struct vm_area_struct *, unsigned long addr,
                  unsigned long size, pgoff_t pgoff);
  extern int file_read_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size);
  int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk);
  extern ssize_t generic_file_aio_read(struct kiocb *, const struct iovec *, unsigned long, loff_t);
  extern ssize_t __generic_file_aio_write(struct kiocb *, const struct iovec *, unsigned long,
                  loff_t *);
  extern ssize_t generic_file_aio_write(struct kiocb *, const struct iovec *, unsigned long, loff_t);
  extern ssize_t generic_file_direct_write(struct kiocb *, const struct iovec *,
                  unsigned long *, loff_t, loff_t *, size_t, size_t);
  extern ssize_t generic_file_buffered_write(struct kiocb *, const struct iovec *,
                  unsigned long, loff_t, loff_t *, size_t, ssize_t);
  extern ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos);
  extern ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos);
  extern int generic_segment_checks(const struct iovec *iov,
                  unsigned long *nr_segs, size_t *count, int access_flags);
  
  /* fs/block_dev.c */
  extern ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov,
                                  unsigned long nr_segs, loff_t pos);
  extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
                          int datasync);
  extern void block_sync_page(struct page *page);
  
  /* fs/splice.c */
  extern ssize_t generic_file_splice_read(struct file *, loff_t *,
                  struct pipe_inode_info *, size_t, unsigned int);
  extern ssize_t default_file_splice_read(struct file *, loff_t *,
                  struct pipe_inode_info *, size_t, unsigned int);
  extern ssize_t generic_file_splice_write(struct pipe_inode_info *,
                  struct file *, loff_t *, size_t, unsigned int);
  extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
                  struct file *out, loff_t *, size_t len, unsigned int flags);
  extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
                  size_t len, unsigned int flags);
  
  extern void
  file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
  extern loff_t noop_llseek(struct file *file, loff_t offset, int whence);
  extern loff_t no_llseek(struct file *file, loff_t offset, int whence);
  extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence);
  extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
                  int whence, loff_t maxsize, loff_t eof);
  extern int generic_file_open(struct inode * inode, struct file * filp);
  extern int nonseekable_open(struct inode * inode, struct file * filp);
  
  #ifdef CONFIG_FS_XIP
  extern ssize_t xip_file_read(struct file *filp, char __user *buf, size_t len,
                               loff_t *ppos);
  extern int xip_file_mmap(struct file * file, struct vm_area_struct * vma);
  extern ssize_t xip_file_write(struct file *filp, const char __user *buf,
                                size_t len, loff_t *ppos);
  extern int xip_truncate_page(struct address_space *mapping, loff_t from);
  #else
  static inline int xip_truncate_page(struct address_space *mapping, loff_t from)
  {
          return 0;
  }
  #endif
  
  #ifdef CONFIG_BLOCK
  typedef void (dio_submit_t)(int rw, struct bio *bio, struct inode *inode,
                              loff_t file_offset);
  
  enum {
          /* need locking between buffered and direct access */
          DIO_LOCKING     = 0x01,
  
          /* filesystem does not support filling holes */
          DIO_SKIP_HOLES  = 0x02,
  };
  
  void dio_end_io(struct bio *bio, int error);
  
  ssize_t __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
          struct block_device *bdev, const struct iovec *iov, loff_t offset,
          unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
          dio_submit_t submit_io, int flags);
  
  static inline ssize_t blockdev_direct_IO(int rw, struct kiocb *iocb,
                  struct inode *inode, const struct iovec *iov, loff_t offset,
                  unsigned long nr_segs, get_block_t get_block)
  {
          return __blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
                                      offset, nr_segs, get_block, NULL, NULL,
                                      DIO_LOCKING | DIO_SKIP_HOLES);
  }
  #endif
  
  void inode_dio_wait(struct inode *inode);
  void inode_dio_done(struct inode *inode);
  
  extern const struct file_operations generic_ro_fops;
  
  #define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))
  
  extern int vfs_readlink(struct dentry *, char __user *, int, const char *);
  extern int vfs_follow_link(struct nameidata *, const char *);
  extern int page_readlink(struct dentry *, char __user *, int);
  extern void *page_follow_link_light(struct dentry *, struct nameidata *);
  extern void page_put_link(struct dentry *, struct nameidata *, void *);
  extern int __page_symlink(struct inode *inode, const char *symname, int len,
                  int nofs);
  extern int page_symlink(struct inode *inode, const char *symname, int len);
  extern const struct inode_operations page_symlink_inode_operations;
  extern int generic_readlink(struct dentry *, char __user *, int);
  extern void generic_fillattr(struct inode *, struct kstat *);
  extern int vfs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
  void __inode_add_bytes(struct inode *inode, loff_t bytes);
  void inode_add_bytes(struct inode *inode, loff_t bytes);
  void inode_sub_bytes(struct inode *inode, loff_t bytes);
  loff_t inode_get_bytes(struct inode *inode);
  void inode_set_bytes(struct inode *inode, loff_t bytes);
  
  extern int vfs_readdir(struct file *, filldir_t, void *);
  
  extern int vfs_stat(const char __user *, struct kstat *);
  extern int vfs_lstat(const char __user *, struct kstat *);
  extern int vfs_fstat(unsigned int, struct kstat *);
  extern int vfs_fstatat(int , const char __user *, struct kstat *, int);
  
  extern int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
                      unsigned long arg);
  extern int __generic_block_fiemap(struct inode *inode,
                                    struct fiemap_extent_info *fieinfo,
                                    loff_t start, loff_t len,
                                    get_block_t *get_block);
  extern int generic_block_fiemap(struct inode *inode,
                                  struct fiemap_extent_info *fieinfo, u64 start,
                                  u64 len, get_block_t *get_block);
  
  extern void get_filesystem(struct file_system_type *fs);
  extern void put_filesystem(struct file_system_type *fs);
  extern struct file_system_type *get_fs_type(const char *name);
  extern struct super_block *get_super(struct block_device *);
  extern struct super_block *get_super_thawed(struct block_device *);
  extern struct super_block *get_active_super(struct block_device *bdev);
  extern void drop_super(struct super_block *sb);
  extern void iterate_supers(void (*)(struct super_block *, void *), void *);
  extern void iterate_supers_type(struct file_system_type *,
                                  void (*)(struct super_block *, void *), void *);
  
  extern int dcache_dir_open(struct inode *, struct file *);
  extern int dcache_dir_close(struct inode *, struct file *);
  extern loff_t dcache_dir_lseek(struct file *, loff_t, int);
  extern int dcache_readdir(struct file *, void *, filldir_t);
  extern int simple_setattr(struct dentry *, struct iattr *);
  extern int simple_getattr(struct vfsmount *, struct dentry *, struct kstat *);
  extern int simple_statfs(struct dentry *, struct kstatfs *);
  extern int simple_open(struct inode *inode, struct file *file);
  extern int simple_link(struct dentry *, struct inode *, struct dentry *);
  extern int simple_unlink(struct inode *, struct dentry *);
  extern int simple_rmdir(struct inode *, struct dentry *);
  extern int simple_rename(struct inode *, struct dentry *, struct inode *, struct dentry *);
  extern int noop_fsync(struct file *, loff_t, loff_t, int);
  extern int simple_empty(struct dentry *);
  extern int simple_readpage(struct file *file, struct page *page);
  extern int simple_write_begin(struct file *file, struct address_space *mapping,
                          loff_t pos, unsigned len, unsigned flags,
                          struct page **pagep, void **fsdata);
  extern int simple_write_end(struct file *file, struct address_space *mapping,
                          loff_t pos, unsigned len, unsigned copied,
                          struct page *page, void *fsdata);
  
  extern struct dentry *simple_lookup(struct inode *, struct dentry *, unsigned int flags);
  extern ssize_t generic_read_dir(struct file *, char __user *, size_t, loff_t *);
  extern const struct file_operations simple_dir_operations;
  extern const struct inode_operations simple_dir_inode_operations;
  struct tree_descr { char *name; const struct file_operations *ops; int mode; };
  struct dentry *d_alloc_name(struct dentry *, const char *);
  extern int simple_fill_super(struct super_block *, unsigned long, struct tree_descr *);
  extern int simple_pin_fs(struct file_system_type *, struct vfsmount **mount, int *count);
  extern void simple_release_fs(struct vfsmount **mount, int *count);
  
  extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
                          loff_t *ppos, const void *from, size_t available);
  extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
                  const void __user *from, size_t count);
  
  extern int generic_file_fsync(struct file *, loff_t, loff_t, int);
  
  extern int generic_check_addressable(unsigned, u64);
  
  #ifdef CONFIG_MIGRATION
  extern int buffer_migrate_page(struct address_space *,
                                  struct page *, struct page *,
                                  enum migrate_mode);
  #else
  #define buffer_migrate_page NULL
  #endif
  
  extern int inode_change_ok(const struct inode *, struct iattr *);
  extern int inode_newsize_ok(const struct inode *, loff_t offset);
  extern void setattr_copy(struct inode *inode, const struct iattr *attr);
  
  extern int file_update_time(struct file *file);
  
  extern int generic_show_options(struct seq_file *m, struct dentry *root);
  extern void save_mount_options(struct super_block *sb, char *options);
  extern void replace_mount_options(struct super_block *sb, char *options);
  
  static inline ino_t parent_ino(struct dentry *dentry)
  {
          ino_t res;
  
          /*
           * Don't strictly need d_lock here? If the parent ino could change
           * then surely we'd have a deeper race in the caller?
           */
          spin_lock(&dentry->d_lock);
          res = dentry->d_parent->d_inode->i_ino;
          spin_unlock(&dentry->d_lock);
          return res;
  }
  
  /* Transaction based IO helpers */
  
  /*
   * An argresp is stored in an allocated page and holds the
   * size of the argument or response, along with its content
   */
  struct simple_transaction_argresp {
          ssize_t size;
          char data[0];
  };
  
  #define SIMPLE_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct simple_transaction_argresp))
  
  char *simple_transaction_get(struct file *file, const char __user *buf,
                                  size_t size);
  ssize_t simple_transaction_read(struct file *file, char __user *buf,
                                  size_t size, loff_t *pos);
  int simple_transaction_release(struct inode *inode, struct file *file);
  
  void simple_transaction_set(struct file *file, size_t n);
  
  /*
   * simple attribute files
   *
   * These attributes behave similar to those in sysfs:
   *
   * Writing to an attribute immediately sets a value, an open file can be
   * written to multiple times.
   *
   * Reading from an attribute creates a buffer from the value that might get
   * read with multiple read calls. When the attribute has been read
   * completely, no further read calls are possible until the file is opened
   * again.
   *
   * All attributes contain a text representation of a numeric value
   * that are accessed with the get() and set() functions.
   */
  #define DEFINE_SIMPLE_ATTRIBUTE(__fops, __get, __set, __fmt)            \
  static int __fops ## _open(struct inode *inode, struct file *file)      \
  {                                                                       \
          __simple_attr_check_format(__fmt, 0ull);                        \
          return simple_attr_open(inode, file, __get, __set, __fmt);      \
  }                                                                       \
  static const struct file_operations __fops = {                          \
          .owner   = THIS_MODULE,                                         \
          .open    = __fops ## _open,                                     \
          .release = simple_attr_release,                                 \
          .read    = simple_attr_read,                                    \
          .write   = simple_attr_write,                                   \
          .llseek  = generic_file_llseek,                                 \
  };
  
  static inline __printf(1, 2)
  void __simple_attr_check_format(const char *fmt, ...)
  {
          /* don't do anything, just let the compiler check the arguments; */
  }
  
  int simple_attr_open(struct inode *inode, struct file *file,
                       int (*get)(void *, u64 *), int (*set)(void *, u64),
                       const char *fmt);
  int simple_attr_release(struct inode *inode, struct file *file);
  ssize_t simple_attr_read(struct file *file, char __user *buf,
                           size_t len, loff_t *ppos);
  ssize_t simple_attr_write(struct file *file, const char __user *buf,
                            size_t len, loff_t *ppos);
  
  struct ctl_table;
  int proc_nr_files(struct ctl_table *table, int write,
                    void __user *buffer, size_t *lenp, loff_t *ppos);
  int proc_nr_dentry(struct ctl_table *table, int write,
                    void __user *buffer, size_t *lenp, loff_t *ppos);
  int proc_nr_inodes(struct ctl_table *table, int write,
                     void __user *buffer, size_t *lenp, loff_t *ppos);
  int __init get_filesystem_list(char *buf);
  
  #define __FMODE_EXEC            ((__force int) FMODE_EXEC)
  #define __FMODE_NONOTIFY        ((__force int) FMODE_NONOTIFY)
  
  #define ACC_MODE(x) ("\004\002\006\006"[(x)&O_ACCMODE])
  #define OPEN_FMODE(flag) ((__force fmode_t)(((flag + 1) & O_ACCMODE) | \
                                              (flag & __FMODE_NONOTIFY)))
  
  static inline int is_sxid(umode_t mode)
  {
          return (mode & S_ISUID) || ((mode & S_ISGID) && (mode & S_IXGRP));
  }
  
  static inline void inode_has_no_xattr(struct inode *inode)
  {
          if (!is_sxid(inode->i_mode) && (inode->i_sb->s_flags & MS_NOSEC))
                  inode->i_flags |= S_NOSEC;
  }
  
  #endif /* _LINUX_FS_H */

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