The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/fs/inode.c

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    1 /*
    2  * (C) 1997 Linus Torvalds
    3  * (C) 1999 Andrea Arcangeli <andrea@suse.de> (dynamic inode allocation)
    4  */
    5 #include <linux/export.h>
    6 #include <linux/fs.h>
    7 #include <linux/mm.h>
    8 #include <linux/backing-dev.h>
    9 #include <linux/hash.h>
   10 #include <linux/swap.h>
   11 #include <linux/security.h>
   12 #include <linux/cdev.h>
   13 #include <linux/bootmem.h>
   14 #include <linux/fsnotify.h>
   15 #include <linux/mount.h>
   16 #include <linux/posix_acl.h>
   17 #include <linux/prefetch.h>
   18 #include <linux/buffer_head.h> /* for inode_has_buffers */
   19 #include <linux/ratelimit.h>
   20 #include "internal.h"
   21 
   22 /*
   23  * Inode locking rules:
   24  *
   25  * inode->i_lock protects:
   26  *   inode->i_state, inode->i_hash, __iget()
   27  * inode->i_sb->s_inode_lru_lock protects:
   28  *   inode->i_sb->s_inode_lru, inode->i_lru
   29  * inode_sb_list_lock protects:
   30  *   sb->s_inodes, inode->i_sb_list
   31  * bdi->wb.list_lock protects:
   32  *   bdi->wb.b_{dirty,io,more_io}, inode->i_wb_list
   33  * inode_hash_lock protects:
   34  *   inode_hashtable, inode->i_hash
   35  *
   36  * Lock ordering:
   37  *
   38  * inode_sb_list_lock
   39  *   inode->i_lock
   40  *     inode->i_sb->s_inode_lru_lock
   41  *
   42  * bdi->wb.list_lock
   43  *   inode->i_lock
   44  *
   45  * inode_hash_lock
   46  *   inode_sb_list_lock
   47  *   inode->i_lock
   48  *
   49  * iunique_lock
   50  *   inode_hash_lock
   51  */
   52 
   53 static unsigned int i_hash_mask __read_mostly;
   54 static unsigned int i_hash_shift __read_mostly;
   55 static struct hlist_head *inode_hashtable __read_mostly;
   56 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);
   57 
   58 __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_sb_list_lock);
   59 
   60 /*
   61  * Empty aops. Can be used for the cases where the user does not
   62  * define any of the address_space operations.
   63  */
   64 const struct address_space_operations empty_aops = {
   65 };
   66 EXPORT_SYMBOL(empty_aops);
   67 
   68 /*
   69  * Statistics gathering..
   70  */
   71 struct inodes_stat_t inodes_stat;
   72 
   73 static DEFINE_PER_CPU(unsigned int, nr_inodes);
   74 static DEFINE_PER_CPU(unsigned int, nr_unused);
   75 
   76 static struct kmem_cache *inode_cachep __read_mostly;
   77 
   78 static int get_nr_inodes(void)
   79 {
   80         int i;
   81         int sum = 0;
   82         for_each_possible_cpu(i)
   83                 sum += per_cpu(nr_inodes, i);
   84         return sum < 0 ? 0 : sum;
   85 }
   86 
   87 static inline int get_nr_inodes_unused(void)
   88 {
   89         int i;
   90         int sum = 0;
   91         for_each_possible_cpu(i)
   92                 sum += per_cpu(nr_unused, i);
   93         return sum < 0 ? 0 : sum;
   94 }
   95 
   96 int get_nr_dirty_inodes(void)
   97 {
   98         /* not actually dirty inodes, but a wild approximation */
   99         int nr_dirty = get_nr_inodes() - get_nr_inodes_unused();
  100         return nr_dirty > 0 ? nr_dirty : 0;
  101 }
  102 
  103 /*
  104  * Handle nr_inode sysctl
  105  */
  106 #ifdef CONFIG_SYSCTL
  107 int proc_nr_inodes(ctl_table *table, int write,
  108                    void __user *buffer, size_t *lenp, loff_t *ppos)
  109 {
  110         inodes_stat.nr_inodes = get_nr_inodes();
  111         inodes_stat.nr_unused = get_nr_inodes_unused();
  112         return proc_dointvec(table, write, buffer, lenp, ppos);
  113 }
  114 #endif
  115 
  116 /**
  117  * inode_init_always - perform inode structure intialisation
  118  * @sb: superblock inode belongs to
  119  * @inode: inode to initialise
  120  *
  121  * These are initializations that need to be done on every inode
  122  * allocation as the fields are not initialised by slab allocation.
  123  */
  124 int inode_init_always(struct super_block *sb, struct inode *inode)
  125 {
  126         static const struct inode_operations empty_iops;
  127         static const struct file_operations empty_fops;
  128         struct address_space *const mapping = &inode->i_data;
  129 
  130         inode->i_sb = sb;
  131         inode->i_blkbits = sb->s_blocksize_bits;
  132         inode->i_flags = 0;
  133         atomic_set(&inode->i_count, 1);
  134         inode->i_op = &empty_iops;
  135         inode->i_fop = &empty_fops;
  136         inode->__i_nlink = 1;
  137         inode->i_opflags = 0;
  138         i_uid_write(inode, 0);
  139         i_gid_write(inode, 0);
  140         atomic_set(&inode->i_writecount, 0);
  141         inode->i_size = 0;
  142         inode->i_blocks = 0;
  143         inode->i_bytes = 0;
  144         inode->i_generation = 0;
  145 #ifdef CONFIG_QUOTA
  146         memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
  147 #endif
  148         inode->i_pipe = NULL;
  149         inode->i_bdev = NULL;
  150         inode->i_cdev = NULL;
  151         inode->i_rdev = 0;
  152         inode->dirtied_when = 0;
  153 
  154         if (security_inode_alloc(inode))
  155                 goto out;
  156         spin_lock_init(&inode->i_lock);
  157         lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);
  158 
  159         mutex_init(&inode->i_mutex);
  160         lockdep_set_class(&inode->i_mutex, &sb->s_type->i_mutex_key);
  161 
  162         atomic_set(&inode->i_dio_count, 0);
  163 
  164         mapping->a_ops = &empty_aops;
  165         mapping->host = inode;
  166         mapping->flags = 0;
  167         mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
  168         mapping->private_data = NULL;
  169         mapping->backing_dev_info = &default_backing_dev_info;
  170         mapping->writeback_index = 0;
  171 
  172         /*
  173          * If the block_device provides a backing_dev_info for client
  174          * inodes then use that.  Otherwise the inode share the bdev's
  175          * backing_dev_info.
  176          */
  177         if (sb->s_bdev) {
  178                 struct backing_dev_info *bdi;
  179 
  180                 bdi = sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
  181                 mapping->backing_dev_info = bdi;
  182         }
  183         inode->i_private = NULL;
  184         inode->i_mapping = mapping;
  185         INIT_HLIST_HEAD(&inode->i_dentry);      /* buggered by rcu freeing */
  186 #ifdef CONFIG_FS_POSIX_ACL
  187         inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
  188 #endif
  189 
  190 #ifdef CONFIG_FSNOTIFY
  191         inode->i_fsnotify_mask = 0;
  192 #endif
  193 
  194         this_cpu_inc(nr_inodes);
  195 
  196         return 0;
  197 out:
  198         return -ENOMEM;
  199 }
  200 EXPORT_SYMBOL(inode_init_always);
  201 
  202 static struct inode *alloc_inode(struct super_block *sb)
  203 {
  204         struct inode *inode;
  205 
  206         if (sb->s_op->alloc_inode)
  207                 inode = sb->s_op->alloc_inode(sb);
  208         else
  209                 inode = kmem_cache_alloc(inode_cachep, GFP_KERNEL);
  210 
  211         if (!inode)
  212                 return NULL;
  213 
  214         if (unlikely(inode_init_always(sb, inode))) {
  215                 if (inode->i_sb->s_op->destroy_inode)
  216                         inode->i_sb->s_op->destroy_inode(inode);
  217                 else
  218                         kmem_cache_free(inode_cachep, inode);
  219                 return NULL;
  220         }
  221 
  222         return inode;
  223 }
  224 
  225 void free_inode_nonrcu(struct inode *inode)
  226 {
  227         kmem_cache_free(inode_cachep, inode);
  228 }
  229 EXPORT_SYMBOL(free_inode_nonrcu);
  230 
  231 void __destroy_inode(struct inode *inode)
  232 {
  233         BUG_ON(inode_has_buffers(inode));
  234         security_inode_free(inode);
  235         fsnotify_inode_delete(inode);
  236         if (!inode->i_nlink) {
  237                 WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);
  238                 atomic_long_dec(&inode->i_sb->s_remove_count);
  239         }
  240 
  241 #ifdef CONFIG_FS_POSIX_ACL
  242         if (inode->i_acl && inode->i_acl != ACL_NOT_CACHED)
  243                 posix_acl_release(inode->i_acl);
  244         if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
  245                 posix_acl_release(inode->i_default_acl);
  246 #endif
  247         this_cpu_dec(nr_inodes);
  248 }
  249 EXPORT_SYMBOL(__destroy_inode);
  250 
  251 static void i_callback(struct rcu_head *head)
  252 {
  253         struct inode *inode = container_of(head, struct inode, i_rcu);
  254         kmem_cache_free(inode_cachep, inode);
  255 }
  256 
  257 static void destroy_inode(struct inode *inode)
  258 {
  259         BUG_ON(!list_empty(&inode->i_lru));
  260         __destroy_inode(inode);
  261         if (inode->i_sb->s_op->destroy_inode)
  262                 inode->i_sb->s_op->destroy_inode(inode);
  263         else
  264                 call_rcu(&inode->i_rcu, i_callback);
  265 }
  266 
  267 /**
  268  * drop_nlink - directly drop an inode's link count
  269  * @inode: inode
  270  *
  271  * This is a low-level filesystem helper to replace any
  272  * direct filesystem manipulation of i_nlink.  In cases
  273  * where we are attempting to track writes to the
  274  * filesystem, a decrement to zero means an imminent
  275  * write when the file is truncated and actually unlinked
  276  * on the filesystem.
  277  */
  278 void drop_nlink(struct inode *inode)
  279 {
  280         WARN_ON(inode->i_nlink == 0);
  281         inode->__i_nlink--;
  282         if (!inode->i_nlink)
  283                 atomic_long_inc(&inode->i_sb->s_remove_count);
  284 }
  285 EXPORT_SYMBOL(drop_nlink);
  286 
  287 /**
  288  * clear_nlink - directly zero an inode's link count
  289  * @inode: inode
  290  *
  291  * This is a low-level filesystem helper to replace any
  292  * direct filesystem manipulation of i_nlink.  See
  293  * drop_nlink() for why we care about i_nlink hitting zero.
  294  */
  295 void clear_nlink(struct inode *inode)
  296 {
  297         if (inode->i_nlink) {
  298                 inode->__i_nlink = 0;
  299                 atomic_long_inc(&inode->i_sb->s_remove_count);
  300         }
  301 }
  302 EXPORT_SYMBOL(clear_nlink);
  303 
  304 /**
  305  * set_nlink - directly set an inode's link count
  306  * @inode: inode
  307  * @nlink: new nlink (should be non-zero)
  308  *
  309  * This is a low-level filesystem helper to replace any
  310  * direct filesystem manipulation of i_nlink.
  311  */
  312 void set_nlink(struct inode *inode, unsigned int nlink)
  313 {
  314         if (!nlink) {
  315                 clear_nlink(inode);
  316         } else {
  317                 /* Yes, some filesystems do change nlink from zero to one */
  318                 if (inode->i_nlink == 0)
  319                         atomic_long_dec(&inode->i_sb->s_remove_count);
  320 
  321                 inode->__i_nlink = nlink;
  322         }
  323 }
  324 EXPORT_SYMBOL(set_nlink);
  325 
  326 /**
  327  * inc_nlink - directly increment an inode's link count
  328  * @inode: inode
  329  *
  330  * This is a low-level filesystem helper to replace any
  331  * direct filesystem manipulation of i_nlink.  Currently,
  332  * it is only here for parity with dec_nlink().
  333  */
  334 void inc_nlink(struct inode *inode)
  335 {
  336         if (WARN_ON(inode->i_nlink == 0))
  337                 atomic_long_dec(&inode->i_sb->s_remove_count);
  338 
  339         inode->__i_nlink++;
  340 }
  341 EXPORT_SYMBOL(inc_nlink);
  342 
  343 void address_space_init_once(struct address_space *mapping)
  344 {
  345         memset(mapping, 0, sizeof(*mapping));
  346         INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC);
  347         spin_lock_init(&mapping->tree_lock);
  348         mutex_init(&mapping->i_mmap_mutex);
  349         INIT_LIST_HEAD(&mapping->private_list);
  350         spin_lock_init(&mapping->private_lock);
  351         mapping->i_mmap = RB_ROOT;
  352         INIT_LIST_HEAD(&mapping->i_mmap_nonlinear);
  353 }
  354 EXPORT_SYMBOL(address_space_init_once);
  355 
  356 /*
  357  * These are initializations that only need to be done
  358  * once, because the fields are idempotent across use
  359  * of the inode, so let the slab aware of that.
  360  */
  361 void inode_init_once(struct inode *inode)
  362 {
  363         memset(inode, 0, sizeof(*inode));
  364         INIT_HLIST_NODE(&inode->i_hash);
  365         INIT_LIST_HEAD(&inode->i_devices);
  366         INIT_LIST_HEAD(&inode->i_wb_list);
  367         INIT_LIST_HEAD(&inode->i_lru);
  368         address_space_init_once(&inode->i_data);
  369         i_size_ordered_init(inode);
  370 #ifdef CONFIG_FSNOTIFY
  371         INIT_HLIST_HEAD(&inode->i_fsnotify_marks);
  372 #endif
  373 }
  374 EXPORT_SYMBOL(inode_init_once);
  375 
  376 static void init_once(void *foo)
  377 {
  378         struct inode *inode = (struct inode *) foo;
  379 
  380         inode_init_once(inode);
  381 }
  382 
  383 /*
  384  * inode->i_lock must be held
  385  */
  386 void __iget(struct inode *inode)
  387 {
  388         atomic_inc(&inode->i_count);
  389 }
  390 
  391 /*
  392  * get additional reference to inode; caller must already hold one.
  393  */
  394 void ihold(struct inode *inode)
  395 {
  396         WARN_ON(atomic_inc_return(&inode->i_count) < 2);
  397 }
  398 EXPORT_SYMBOL(ihold);
  399 
  400 static void inode_lru_list_add(struct inode *inode)
  401 {
  402         spin_lock(&inode->i_sb->s_inode_lru_lock);
  403         if (list_empty(&inode->i_lru)) {
  404                 list_add(&inode->i_lru, &inode->i_sb->s_inode_lru);
  405                 inode->i_sb->s_nr_inodes_unused++;
  406                 this_cpu_inc(nr_unused);
  407         }
  408         spin_unlock(&inode->i_sb->s_inode_lru_lock);
  409 }
  410 
  411 /*
  412  * Add inode to LRU if needed (inode is unused and clean).
  413  *
  414  * Needs inode->i_lock held.
  415  */
  416 void inode_add_lru(struct inode *inode)
  417 {
  418         if (!(inode->i_state & (I_DIRTY | I_SYNC | I_FREEING | I_WILL_FREE)) &&
  419             !atomic_read(&inode->i_count) && inode->i_sb->s_flags & MS_ACTIVE)
  420                 inode_lru_list_add(inode);
  421 }
  422 
  423 
  424 static void inode_lru_list_del(struct inode *inode)
  425 {
  426         spin_lock(&inode->i_sb->s_inode_lru_lock);
  427         if (!list_empty(&inode->i_lru)) {
  428                 list_del_init(&inode->i_lru);
  429                 inode->i_sb->s_nr_inodes_unused--;
  430                 this_cpu_dec(nr_unused);
  431         }
  432         spin_unlock(&inode->i_sb->s_inode_lru_lock);
  433 }
  434 
  435 /**
  436  * inode_sb_list_add - add inode to the superblock list of inodes
  437  * @inode: inode to add
  438  */
  439 void inode_sb_list_add(struct inode *inode)
  440 {
  441         spin_lock(&inode_sb_list_lock);
  442         list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
  443         spin_unlock(&inode_sb_list_lock);
  444 }
  445 EXPORT_SYMBOL_GPL(inode_sb_list_add);
  446 
  447 static inline void inode_sb_list_del(struct inode *inode)
  448 {
  449         if (!list_empty(&inode->i_sb_list)) {
  450                 spin_lock(&inode_sb_list_lock);
  451                 list_del_init(&inode->i_sb_list);
  452                 spin_unlock(&inode_sb_list_lock);
  453         }
  454 }
  455 
  456 static unsigned long hash(struct super_block *sb, unsigned long hashval)
  457 {
  458         unsigned long tmp;
  459 
  460         tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
  461                         L1_CACHE_BYTES;
  462         tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> i_hash_shift);
  463         return tmp & i_hash_mask;
  464 }
  465 
  466 /**
  467  *      __insert_inode_hash - hash an inode
  468  *      @inode: unhashed inode
  469  *      @hashval: unsigned long value used to locate this object in the
  470  *              inode_hashtable.
  471  *
  472  *      Add an inode to the inode hash for this superblock.
  473  */
  474 void __insert_inode_hash(struct inode *inode, unsigned long hashval)
  475 {
  476         struct hlist_head *b = inode_hashtable + hash(inode->i_sb, hashval);
  477 
  478         spin_lock(&inode_hash_lock);
  479         spin_lock(&inode->i_lock);
  480         hlist_add_head(&inode->i_hash, b);
  481         spin_unlock(&inode->i_lock);
  482         spin_unlock(&inode_hash_lock);
  483 }
  484 EXPORT_SYMBOL(__insert_inode_hash);
  485 
  486 /**
  487  *      __remove_inode_hash - remove an inode from the hash
  488  *      @inode: inode to unhash
  489  *
  490  *      Remove an inode from the superblock.
  491  */
  492 void __remove_inode_hash(struct inode *inode)
  493 {
  494         spin_lock(&inode_hash_lock);
  495         spin_lock(&inode->i_lock);
  496         hlist_del_init(&inode->i_hash);
  497         spin_unlock(&inode->i_lock);
  498         spin_unlock(&inode_hash_lock);
  499 }
  500 EXPORT_SYMBOL(__remove_inode_hash);
  501 
  502 void clear_inode(struct inode *inode)
  503 {
  504         might_sleep();
  505         /*
  506          * We have to cycle tree_lock here because reclaim can be still in the
  507          * process of removing the last page (in __delete_from_page_cache())
  508          * and we must not free mapping under it.
  509          */
  510         spin_lock_irq(&inode->i_data.tree_lock);
  511         BUG_ON(inode->i_data.nrpages);
  512         spin_unlock_irq(&inode->i_data.tree_lock);
  513         BUG_ON(!list_empty(&inode->i_data.private_list));
  514         BUG_ON(!(inode->i_state & I_FREEING));
  515         BUG_ON(inode->i_state & I_CLEAR);
  516         /* don't need i_lock here, no concurrent mods to i_state */
  517         inode->i_state = I_FREEING | I_CLEAR;
  518 }
  519 EXPORT_SYMBOL(clear_inode);
  520 
  521 /*
  522  * Free the inode passed in, removing it from the lists it is still connected
  523  * to. We remove any pages still attached to the inode and wait for any IO that
  524  * is still in progress before finally destroying the inode.
  525  *
  526  * An inode must already be marked I_FREEING so that we avoid the inode being
  527  * moved back onto lists if we race with other code that manipulates the lists
  528  * (e.g. writeback_single_inode). The caller is responsible for setting this.
  529  *
  530  * An inode must already be removed from the LRU list before being evicted from
  531  * the cache. This should occur atomically with setting the I_FREEING state
  532  * flag, so no inodes here should ever be on the LRU when being evicted.
  533  */
  534 static void evict(struct inode *inode)
  535 {
  536         const struct super_operations *op = inode->i_sb->s_op;
  537 
  538         BUG_ON(!(inode->i_state & I_FREEING));
  539         BUG_ON(!list_empty(&inode->i_lru));
  540 
  541         if (!list_empty(&inode->i_wb_list))
  542                 inode_wb_list_del(inode);
  543 
  544         inode_sb_list_del(inode);
  545 
  546         /*
  547          * Wait for flusher thread to be done with the inode so that filesystem
  548          * does not start destroying it while writeback is still running. Since
  549          * the inode has I_FREEING set, flusher thread won't start new work on
  550          * the inode.  We just have to wait for running writeback to finish.
  551          */
  552         inode_wait_for_writeback(inode);
  553 
  554         if (op->evict_inode) {
  555                 op->evict_inode(inode);
  556         } else {
  557                 if (inode->i_data.nrpages)
  558                         truncate_inode_pages(&inode->i_data, 0);
  559                 clear_inode(inode);
  560         }
  561         if (S_ISBLK(inode->i_mode) && inode->i_bdev)
  562                 bd_forget(inode);
  563         if (S_ISCHR(inode->i_mode) && inode->i_cdev)
  564                 cd_forget(inode);
  565 
  566         remove_inode_hash(inode);
  567 
  568         spin_lock(&inode->i_lock);
  569         wake_up_bit(&inode->i_state, __I_NEW);
  570         BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
  571         spin_unlock(&inode->i_lock);
  572 
  573         destroy_inode(inode);
  574 }
  575 
  576 /*
  577  * dispose_list - dispose of the contents of a local list
  578  * @head: the head of the list to free
  579  *
  580  * Dispose-list gets a local list with local inodes in it, so it doesn't
  581  * need to worry about list corruption and SMP locks.
  582  */
  583 static void dispose_list(struct list_head *head)
  584 {
  585         while (!list_empty(head)) {
  586                 struct inode *inode;
  587 
  588                 inode = list_first_entry(head, struct inode, i_lru);
  589                 list_del_init(&inode->i_lru);
  590 
  591                 evict(inode);
  592         }
  593 }
  594 
  595 /**
  596  * evict_inodes - evict all evictable inodes for a superblock
  597  * @sb:         superblock to operate on
  598  *
  599  * Make sure that no inodes with zero refcount are retained.  This is
  600  * called by superblock shutdown after having MS_ACTIVE flag removed,
  601  * so any inode reaching zero refcount during or after that call will
  602  * be immediately evicted.
  603  */
  604 void evict_inodes(struct super_block *sb)
  605 {
  606         struct inode *inode, *next;
  607         LIST_HEAD(dispose);
  608 
  609         spin_lock(&inode_sb_list_lock);
  610         list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
  611                 if (atomic_read(&inode->i_count))
  612                         continue;
  613 
  614                 spin_lock(&inode->i_lock);
  615                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
  616                         spin_unlock(&inode->i_lock);
  617                         continue;
  618                 }
  619 
  620                 inode->i_state |= I_FREEING;
  621                 inode_lru_list_del(inode);
  622                 spin_unlock(&inode->i_lock);
  623                 list_add(&inode->i_lru, &dispose);
  624         }
  625         spin_unlock(&inode_sb_list_lock);
  626 
  627         dispose_list(&dispose);
  628 }
  629 
  630 /**
  631  * invalidate_inodes    - attempt to free all inodes on a superblock
  632  * @sb:         superblock to operate on
  633  * @kill_dirty: flag to guide handling of dirty inodes
  634  *
  635  * Attempts to free all inodes for a given superblock.  If there were any
  636  * busy inodes return a non-zero value, else zero.
  637  * If @kill_dirty is set, discard dirty inodes too, otherwise treat
  638  * them as busy.
  639  */
  640 int invalidate_inodes(struct super_block *sb, bool kill_dirty)
  641 {
  642         int busy = 0;
  643         struct inode *inode, *next;
  644         LIST_HEAD(dispose);
  645 
  646         spin_lock(&inode_sb_list_lock);
  647         list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
  648                 spin_lock(&inode->i_lock);
  649                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
  650                         spin_unlock(&inode->i_lock);
  651                         continue;
  652                 }
  653                 if (inode->i_state & I_DIRTY && !kill_dirty) {
  654                         spin_unlock(&inode->i_lock);
  655                         busy = 1;
  656                         continue;
  657                 }
  658                 if (atomic_read(&inode->i_count)) {
  659                         spin_unlock(&inode->i_lock);
  660                         busy = 1;
  661                         continue;
  662                 }
  663 
  664                 inode->i_state |= I_FREEING;
  665                 inode_lru_list_del(inode);
  666                 spin_unlock(&inode->i_lock);
  667                 list_add(&inode->i_lru, &dispose);
  668         }
  669         spin_unlock(&inode_sb_list_lock);
  670 
  671         dispose_list(&dispose);
  672 
  673         return busy;
  674 }
  675 
  676 static int can_unuse(struct inode *inode)
  677 {
  678         if (inode->i_state & ~I_REFERENCED)
  679                 return 0;
  680         if (inode_has_buffers(inode))
  681                 return 0;
  682         if (atomic_read(&inode->i_count))
  683                 return 0;
  684         if (inode->i_data.nrpages)
  685                 return 0;
  686         return 1;
  687 }
  688 
  689 /*
  690  * Walk the superblock inode LRU for freeable inodes and attempt to free them.
  691  * This is called from the superblock shrinker function with a number of inodes
  692  * to trim from the LRU. Inodes to be freed are moved to a temporary list and
  693  * then are freed outside inode_lock by dispose_list().
  694  *
  695  * Any inodes which are pinned purely because of attached pagecache have their
  696  * pagecache removed.  If the inode has metadata buffers attached to
  697  * mapping->private_list then try to remove them.
  698  *
  699  * If the inode has the I_REFERENCED flag set, then it means that it has been
  700  * used recently - the flag is set in iput_final(). When we encounter such an
  701  * inode, clear the flag and move it to the back of the LRU so it gets another
  702  * pass through the LRU before it gets reclaimed. This is necessary because of
  703  * the fact we are doing lazy LRU updates to minimise lock contention so the
  704  * LRU does not have strict ordering. Hence we don't want to reclaim inodes
  705  * with this flag set because they are the inodes that are out of order.
  706  */
  707 void prune_icache_sb(struct super_block *sb, int nr_to_scan)
  708 {
  709         LIST_HEAD(freeable);
  710         int nr_scanned;
  711         unsigned long reap = 0;
  712 
  713         spin_lock(&sb->s_inode_lru_lock);
  714         for (nr_scanned = nr_to_scan; nr_scanned >= 0; nr_scanned--) {
  715                 struct inode *inode;
  716 
  717                 if (list_empty(&sb->s_inode_lru))
  718                         break;
  719 
  720                 inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
  721 
  722                 /*
  723                  * we are inverting the sb->s_inode_lru_lock/inode->i_lock here,
  724                  * so use a trylock. If we fail to get the lock, just move the
  725                  * inode to the back of the list so we don't spin on it.
  726                  */
  727                 if (!spin_trylock(&inode->i_lock)) {
  728                         list_move_tail(&inode->i_lru, &sb->s_inode_lru);
  729                         continue;
  730                 }
  731 
  732                 /*
  733                  * Referenced or dirty inodes are still in use. Give them
  734                  * another pass through the LRU as we canot reclaim them now.
  735                  */
  736                 if (atomic_read(&inode->i_count) ||
  737                     (inode->i_state & ~I_REFERENCED)) {
  738                         list_del_init(&inode->i_lru);
  739                         spin_unlock(&inode->i_lock);
  740                         sb->s_nr_inodes_unused--;
  741                         this_cpu_dec(nr_unused);
  742                         continue;
  743                 }
  744 
  745                 /* recently referenced inodes get one more pass */
  746                 if (inode->i_state & I_REFERENCED) {
  747                         inode->i_state &= ~I_REFERENCED;
  748                         list_move(&inode->i_lru, &sb->s_inode_lru);
  749                         spin_unlock(&inode->i_lock);
  750                         continue;
  751                 }
  752                 if (inode_has_buffers(inode) || inode->i_data.nrpages) {
  753                         __iget(inode);
  754                         spin_unlock(&inode->i_lock);
  755                         spin_unlock(&sb->s_inode_lru_lock);
  756                         if (remove_inode_buffers(inode))
  757                                 reap += invalidate_mapping_pages(&inode->i_data,
  758                                                                 0, -1);
  759                         iput(inode);
  760                         spin_lock(&sb->s_inode_lru_lock);
  761 
  762                         if (inode != list_entry(sb->s_inode_lru.next,
  763                                                 struct inode, i_lru))
  764                                 continue;       /* wrong inode or list_empty */
  765                         /* avoid lock inversions with trylock */
  766                         if (!spin_trylock(&inode->i_lock))
  767                                 continue;
  768                         if (!can_unuse(inode)) {
  769                                 spin_unlock(&inode->i_lock);
  770                                 continue;
  771                         }
  772                 }
  773                 WARN_ON(inode->i_state & I_NEW);
  774                 inode->i_state |= I_FREEING;
  775                 spin_unlock(&inode->i_lock);
  776 
  777                 list_move(&inode->i_lru, &freeable);
  778                 sb->s_nr_inodes_unused--;
  779                 this_cpu_dec(nr_unused);
  780         }
  781         if (current_is_kswapd())
  782                 __count_vm_events(KSWAPD_INODESTEAL, reap);
  783         else
  784                 __count_vm_events(PGINODESTEAL, reap);
  785         spin_unlock(&sb->s_inode_lru_lock);
  786         if (current->reclaim_state)
  787                 current->reclaim_state->reclaimed_slab += reap;
  788 
  789         dispose_list(&freeable);
  790 }
  791 
  792 static void __wait_on_freeing_inode(struct inode *inode);
  793 /*
  794  * Called with the inode lock held.
  795  */
  796 static struct inode *find_inode(struct super_block *sb,
  797                                 struct hlist_head *head,
  798                                 int (*test)(struct inode *, void *),
  799                                 void *data)
  800 {
  801         struct hlist_node *node;
  802         struct inode *inode = NULL;
  803 
  804 repeat:
  805         hlist_for_each_entry(inode, node, head, i_hash) {
  806                 spin_lock(&inode->i_lock);
  807                 if (inode->i_sb != sb) {
  808                         spin_unlock(&inode->i_lock);
  809                         continue;
  810                 }
  811                 if (!test(inode, data)) {
  812                         spin_unlock(&inode->i_lock);
  813                         continue;
  814                 }
  815                 if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
  816                         __wait_on_freeing_inode(inode);
  817                         goto repeat;
  818                 }
  819                 __iget(inode);
  820                 spin_unlock(&inode->i_lock);
  821                 return inode;
  822         }
  823         return NULL;
  824 }
  825 
  826 /*
  827  * find_inode_fast is the fast path version of find_inode, see the comment at
  828  * iget_locked for details.
  829  */
  830 static struct inode *find_inode_fast(struct super_block *sb,
  831                                 struct hlist_head *head, unsigned long ino)
  832 {
  833         struct hlist_node *node;
  834         struct inode *inode = NULL;
  835 
  836 repeat:
  837         hlist_for_each_entry(inode, node, head, i_hash) {
  838                 spin_lock(&inode->i_lock);
  839                 if (inode->i_ino != ino) {
  840                         spin_unlock(&inode->i_lock);
  841                         continue;
  842                 }
  843                 if (inode->i_sb != sb) {
  844                         spin_unlock(&inode->i_lock);
  845                         continue;
  846                 }
  847                 if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
  848                         __wait_on_freeing_inode(inode);
  849                         goto repeat;
  850                 }
  851                 __iget(inode);
  852                 spin_unlock(&inode->i_lock);
  853                 return inode;
  854         }
  855         return NULL;
  856 }
  857 
  858 /*
  859  * Each cpu owns a range of LAST_INO_BATCH numbers.
  860  * 'shared_last_ino' is dirtied only once out of LAST_INO_BATCH allocations,
  861  * to renew the exhausted range.
  862  *
  863  * This does not significantly increase overflow rate because every CPU can
  864  * consume at most LAST_INO_BATCH-1 unused inode numbers. So there is
  865  * NR_CPUS*(LAST_INO_BATCH-1) wastage. At 4096 and 1024, this is ~0.1% of the
  866  * 2^32 range, and is a worst-case. Even a 50% wastage would only increase
  867  * overflow rate by 2x, which does not seem too significant.
  868  *
  869  * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
  870  * error if st_ino won't fit in target struct field. Use 32bit counter
  871  * here to attempt to avoid that.
  872  */
  873 #define LAST_INO_BATCH 1024
  874 static DEFINE_PER_CPU(unsigned int, last_ino);
  875 
  876 unsigned int get_next_ino(void)
  877 {
  878         unsigned int *p = &get_cpu_var(last_ino);
  879         unsigned int res = *p;
  880 
  881 #ifdef CONFIG_SMP
  882         if (unlikely((res & (LAST_INO_BATCH-1)) == 0)) {
  883                 static atomic_t shared_last_ino;
  884                 int next = atomic_add_return(LAST_INO_BATCH, &shared_last_ino);
  885 
  886                 res = next - LAST_INO_BATCH;
  887         }
  888 #endif
  889 
  890         *p = ++res;
  891         put_cpu_var(last_ino);
  892         return res;
  893 }
  894 EXPORT_SYMBOL(get_next_ino);
  895 
  896 /**
  897  *      new_inode_pseudo        - obtain an inode
  898  *      @sb: superblock
  899  *
  900  *      Allocates a new inode for given superblock.
  901  *      Inode wont be chained in superblock s_inodes list
  902  *      This means :
  903  *      - fs can't be unmount
  904  *      - quotas, fsnotify, writeback can't work
  905  */
  906 struct inode *new_inode_pseudo(struct super_block *sb)
  907 {
  908         struct inode *inode = alloc_inode(sb);
  909 
  910         if (inode) {
  911                 spin_lock(&inode->i_lock);
  912                 inode->i_state = 0;
  913                 spin_unlock(&inode->i_lock);
  914                 INIT_LIST_HEAD(&inode->i_sb_list);
  915         }
  916         return inode;
  917 }
  918 
  919 /**
  920  *      new_inode       - obtain an inode
  921  *      @sb: superblock
  922  *
  923  *      Allocates a new inode for given superblock. The default gfp_mask
  924  *      for allocations related to inode->i_mapping is GFP_HIGHUSER_MOVABLE.
  925  *      If HIGHMEM pages are unsuitable or it is known that pages allocated
  926  *      for the page cache are not reclaimable or migratable,
  927  *      mapping_set_gfp_mask() must be called with suitable flags on the
  928  *      newly created inode's mapping
  929  *
  930  */
  931 struct inode *new_inode(struct super_block *sb)
  932 {
  933         struct inode *inode;
  934 
  935         spin_lock_prefetch(&inode_sb_list_lock);
  936 
  937         inode = new_inode_pseudo(sb);
  938         if (inode)
  939                 inode_sb_list_add(inode);
  940         return inode;
  941 }
  942 EXPORT_SYMBOL(new_inode);
  943 
  944 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  945 void lockdep_annotate_inode_mutex_key(struct inode *inode)
  946 {
  947         if (S_ISDIR(inode->i_mode)) {
  948                 struct file_system_type *type = inode->i_sb->s_type;
  949 
  950                 /* Set new key only if filesystem hasn't already changed it */
  951                 if (lockdep_match_class(&inode->i_mutex, &type->i_mutex_key)) {
  952                         /*
  953                          * ensure nobody is actually holding i_mutex
  954                          */
  955                         mutex_destroy(&inode->i_mutex);
  956                         mutex_init(&inode->i_mutex);
  957                         lockdep_set_class(&inode->i_mutex,
  958                                           &type->i_mutex_dir_key);
  959                 }
  960         }
  961 }
  962 EXPORT_SYMBOL(lockdep_annotate_inode_mutex_key);
  963 #endif
  964 
  965 /**
  966  * unlock_new_inode - clear the I_NEW state and wake up any waiters
  967  * @inode:      new inode to unlock
  968  *
  969  * Called when the inode is fully initialised to clear the new state of the
  970  * inode and wake up anyone waiting for the inode to finish initialisation.
  971  */
  972 void unlock_new_inode(struct inode *inode)
  973 {
  974         lockdep_annotate_inode_mutex_key(inode);
  975         spin_lock(&inode->i_lock);
  976         WARN_ON(!(inode->i_state & I_NEW));
  977         inode->i_state &= ~I_NEW;
  978         smp_mb();
  979         wake_up_bit(&inode->i_state, __I_NEW);
  980         spin_unlock(&inode->i_lock);
  981 }
  982 EXPORT_SYMBOL(unlock_new_inode);
  983 
  984 /**
  985  * iget5_locked - obtain an inode from a mounted file system
  986  * @sb:         super block of file system
  987  * @hashval:    hash value (usually inode number) to get
  988  * @test:       callback used for comparisons between inodes
  989  * @set:        callback used to initialize a new struct inode
  990  * @data:       opaque data pointer to pass to @test and @set
  991  *
  992  * Search for the inode specified by @hashval and @data in the inode cache,
  993  * and if present it is return it with an increased reference count. This is
  994  * a generalized version of iget_locked() for file systems where the inode
  995  * number is not sufficient for unique identification of an inode.
  996  *
  997  * If the inode is not in cache, allocate a new inode and return it locked,
  998  * hashed, and with the I_NEW flag set. The file system gets to fill it in
  999  * before unlocking it via unlock_new_inode().
 1000  *
 1001  * Note both @test and @set are called with the inode_hash_lock held, so can't
 1002  * sleep.
 1003  */
 1004 struct inode *iget5_locked(struct super_block *sb, unsigned long hashval,
 1005                 int (*test)(struct inode *, void *),
 1006                 int (*set)(struct inode *, void *), void *data)
 1007 {
 1008         struct hlist_head *head = inode_hashtable + hash(sb, hashval);
 1009         struct inode *inode;
 1010 
 1011         spin_lock(&inode_hash_lock);
 1012         inode = find_inode(sb, head, test, data);
 1013         spin_unlock(&inode_hash_lock);
 1014 
 1015         if (inode) {
 1016                 wait_on_inode(inode);
 1017                 return inode;
 1018         }
 1019 
 1020         inode = alloc_inode(sb);
 1021         if (inode) {
 1022                 struct inode *old;
 1023 
 1024                 spin_lock(&inode_hash_lock);
 1025                 /* We released the lock, so.. */
 1026                 old = find_inode(sb, head, test, data);
 1027                 if (!old) {
 1028                         if (set(inode, data))
 1029                                 goto set_failed;
 1030 
 1031                         spin_lock(&inode->i_lock);
 1032                         inode->i_state = I_NEW;
 1033                         hlist_add_head(&inode->i_hash, head);
 1034                         spin_unlock(&inode->i_lock);
 1035                         inode_sb_list_add(inode);
 1036                         spin_unlock(&inode_hash_lock);
 1037 
 1038                         /* Return the locked inode with I_NEW set, the
 1039                          * caller is responsible for filling in the contents
 1040                          */
 1041                         return inode;
 1042                 }
 1043 
 1044                 /*
 1045                  * Uhhuh, somebody else created the same inode under
 1046                  * us. Use the old inode instead of the one we just
 1047                  * allocated.
 1048                  */
 1049                 spin_unlock(&inode_hash_lock);
 1050                 destroy_inode(inode);
 1051                 inode = old;
 1052                 wait_on_inode(inode);
 1053         }
 1054         return inode;
 1055 
 1056 set_failed:
 1057         spin_unlock(&inode_hash_lock);
 1058         destroy_inode(inode);
 1059         return NULL;
 1060 }
 1061 EXPORT_SYMBOL(iget5_locked);
 1062 
 1063 /**
 1064  * iget_locked - obtain an inode from a mounted file system
 1065  * @sb:         super block of file system
 1066  * @ino:        inode number to get
 1067  *
 1068  * Search for the inode specified by @ino in the inode cache and if present
 1069  * return it with an increased reference count. This is for file systems
 1070  * where the inode number is sufficient for unique identification of an inode.
 1071  *
 1072  * If the inode is not in cache, allocate a new inode and return it locked,
 1073  * hashed, and with the I_NEW flag set.  The file system gets to fill it in
 1074  * before unlocking it via unlock_new_inode().
 1075  */
 1076 struct inode *iget_locked(struct super_block *sb, unsigned long ino)
 1077 {
 1078         struct hlist_head *head = inode_hashtable + hash(sb, ino);
 1079         struct inode *inode;
 1080 
 1081         spin_lock(&inode_hash_lock);
 1082         inode = find_inode_fast(sb, head, ino);
 1083         spin_unlock(&inode_hash_lock);
 1084         if (inode) {
 1085                 wait_on_inode(inode);
 1086                 return inode;
 1087         }
 1088 
 1089         inode = alloc_inode(sb);
 1090         if (inode) {
 1091                 struct inode *old;
 1092 
 1093                 spin_lock(&inode_hash_lock);
 1094                 /* We released the lock, so.. */
 1095                 old = find_inode_fast(sb, head, ino);
 1096                 if (!old) {
 1097                         inode->i_ino = ino;
 1098                         spin_lock(&inode->i_lock);
 1099                         inode->i_state = I_NEW;
 1100                         hlist_add_head(&inode->i_hash, head);
 1101                         spin_unlock(&inode->i_lock);
 1102                         inode_sb_list_add(inode);
 1103                         spin_unlock(&inode_hash_lock);
 1104 
 1105                         /* Return the locked inode with I_NEW set, the
 1106                          * caller is responsible for filling in the contents
 1107                          */
 1108                         return inode;
 1109                 }
 1110 
 1111                 /*
 1112                  * Uhhuh, somebody else created the same inode under
 1113                  * us. Use the old inode instead of the one we just
 1114                  * allocated.
 1115                  */
 1116                 spin_unlock(&inode_hash_lock);
 1117                 destroy_inode(inode);
 1118                 inode = old;
 1119                 wait_on_inode(inode);
 1120         }
 1121         return inode;
 1122 }
 1123 EXPORT_SYMBOL(iget_locked);
 1124 
 1125 /*
 1126  * search the inode cache for a matching inode number.
 1127  * If we find one, then the inode number we are trying to
 1128  * allocate is not unique and so we should not use it.
 1129  *
 1130  * Returns 1 if the inode number is unique, 0 if it is not.
 1131  */
 1132 static int test_inode_iunique(struct super_block *sb, unsigned long ino)
 1133 {
 1134         struct hlist_head *b = inode_hashtable + hash(sb, ino);
 1135         struct hlist_node *node;
 1136         struct inode *inode;
 1137 
 1138         spin_lock(&inode_hash_lock);
 1139         hlist_for_each_entry(inode, node, b, i_hash) {
 1140                 if (inode->i_ino == ino && inode->i_sb == sb) {
 1141                         spin_unlock(&inode_hash_lock);
 1142                         return 0;
 1143                 }
 1144         }
 1145         spin_unlock(&inode_hash_lock);
 1146 
 1147         return 1;
 1148 }
 1149 
 1150 /**
 1151  *      iunique - get a unique inode number
 1152  *      @sb: superblock
 1153  *      @max_reserved: highest reserved inode number
 1154  *
 1155  *      Obtain an inode number that is unique on the system for a given
 1156  *      superblock. This is used by file systems that have no natural
 1157  *      permanent inode numbering system. An inode number is returned that
 1158  *      is higher than the reserved limit but unique.
 1159  *
 1160  *      BUGS:
 1161  *      With a large number of inodes live on the file system this function
 1162  *      currently becomes quite slow.
 1163  */
 1164 ino_t iunique(struct super_block *sb, ino_t max_reserved)
 1165 {
 1166         /*
 1167          * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
 1168          * error if st_ino won't fit in target struct field. Use 32bit counter
 1169          * here to attempt to avoid that.
 1170          */
 1171         static DEFINE_SPINLOCK(iunique_lock);
 1172         static unsigned int counter;
 1173         ino_t res;
 1174 
 1175         spin_lock(&iunique_lock);
 1176         do {
 1177                 if (counter <= max_reserved)
 1178                         counter = max_reserved + 1;
 1179                 res = counter++;
 1180         } while (!test_inode_iunique(sb, res));
 1181         spin_unlock(&iunique_lock);
 1182 
 1183         return res;
 1184 }
 1185 EXPORT_SYMBOL(iunique);
 1186 
 1187 struct inode *igrab(struct inode *inode)
 1188 {
 1189         spin_lock(&inode->i_lock);
 1190         if (!(inode->i_state & (I_FREEING|I_WILL_FREE))) {
 1191                 __iget(inode);
 1192                 spin_unlock(&inode->i_lock);
 1193         } else {
 1194                 spin_unlock(&inode->i_lock);
 1195                 /*
 1196                  * Handle the case where s_op->clear_inode is not been
 1197                  * called yet, and somebody is calling igrab
 1198                  * while the inode is getting freed.
 1199                  */
 1200                 inode = NULL;
 1201         }
 1202         return inode;
 1203 }
 1204 EXPORT_SYMBOL(igrab);
 1205 
 1206 /**
 1207  * ilookup5_nowait - search for an inode in the inode cache
 1208  * @sb:         super block of file system to search
 1209  * @hashval:    hash value (usually inode number) to search for
 1210  * @test:       callback used for comparisons between inodes
 1211  * @data:       opaque data pointer to pass to @test
 1212  *
 1213  * Search for the inode specified by @hashval and @data in the inode cache.
 1214  * If the inode is in the cache, the inode is returned with an incremented
 1215  * reference count.
 1216  *
 1217  * Note: I_NEW is not waited upon so you have to be very careful what you do
 1218  * with the returned inode.  You probably should be using ilookup5() instead.
 1219  *
 1220  * Note2: @test is called with the inode_hash_lock held, so can't sleep.
 1221  */
 1222 struct inode *ilookup5_nowait(struct super_block *sb, unsigned long hashval,
 1223                 int (*test)(struct inode *, void *), void *data)
 1224 {
 1225         struct hlist_head *head = inode_hashtable + hash(sb, hashval);
 1226         struct inode *inode;
 1227 
 1228         spin_lock(&inode_hash_lock);
 1229         inode = find_inode(sb, head, test, data);
 1230         spin_unlock(&inode_hash_lock);
 1231 
 1232         return inode;
 1233 }
 1234 EXPORT_SYMBOL(ilookup5_nowait);
 1235 
 1236 /**
 1237  * ilookup5 - search for an inode in the inode cache
 1238  * @sb:         super block of file system to search
 1239  * @hashval:    hash value (usually inode number) to search for
 1240  * @test:       callback used for comparisons between inodes
 1241  * @data:       opaque data pointer to pass to @test
 1242  *
 1243  * Search for the inode specified by @hashval and @data in the inode cache,
 1244  * and if the inode is in the cache, return the inode with an incremented
 1245  * reference count.  Waits on I_NEW before returning the inode.
 1246  * returned with an incremented reference count.
 1247  *
 1248  * This is a generalized version of ilookup() for file systems where the
 1249  * inode number is not sufficient for unique identification of an inode.
 1250  *
 1251  * Note: @test is called with the inode_hash_lock held, so can't sleep.
 1252  */
 1253 struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
 1254                 int (*test)(struct inode *, void *), void *data)
 1255 {
 1256         struct inode *inode = ilookup5_nowait(sb, hashval, test, data);
 1257 
 1258         if (inode)
 1259                 wait_on_inode(inode);
 1260         return inode;
 1261 }
 1262 EXPORT_SYMBOL(ilookup5);
 1263 
 1264 /**
 1265  * ilookup - search for an inode in the inode cache
 1266  * @sb:         super block of file system to search
 1267  * @ino:        inode number to search for
 1268  *
 1269  * Search for the inode @ino in the inode cache, and if the inode is in the
 1270  * cache, the inode is returned with an incremented reference count.
 1271  */
 1272 struct inode *ilookup(struct super_block *sb, unsigned long ino)
 1273 {
 1274         struct hlist_head *head = inode_hashtable + hash(sb, ino);
 1275         struct inode *inode;
 1276 
 1277         spin_lock(&inode_hash_lock);
 1278         inode = find_inode_fast(sb, head, ino);
 1279         spin_unlock(&inode_hash_lock);
 1280 
 1281         if (inode)
 1282                 wait_on_inode(inode);
 1283         return inode;
 1284 }
 1285 EXPORT_SYMBOL(ilookup);
 1286 
 1287 int insert_inode_locked(struct inode *inode)
 1288 {
 1289         struct super_block *sb = inode->i_sb;
 1290         ino_t ino = inode->i_ino;
 1291         struct hlist_head *head = inode_hashtable + hash(sb, ino);
 1292 
 1293         while (1) {
 1294                 struct hlist_node *node;
 1295                 struct inode *old = NULL;
 1296                 spin_lock(&inode_hash_lock);
 1297                 hlist_for_each_entry(old, node, head, i_hash) {
 1298                         if (old->i_ino != ino)
 1299                                 continue;
 1300                         if (old->i_sb != sb)
 1301                                 continue;
 1302                         spin_lock(&old->i_lock);
 1303                         if (old->i_state & (I_FREEING|I_WILL_FREE)) {
 1304                                 spin_unlock(&old->i_lock);
 1305                                 continue;
 1306                         }
 1307                         break;
 1308                 }
 1309                 if (likely(!node)) {
 1310                         spin_lock(&inode->i_lock);
 1311                         inode->i_state |= I_NEW;
 1312                         hlist_add_head(&inode->i_hash, head);
 1313                         spin_unlock(&inode->i_lock);
 1314                         spin_unlock(&inode_hash_lock);
 1315                         return 0;
 1316                 }
 1317                 __iget(old);
 1318                 spin_unlock(&old->i_lock);
 1319                 spin_unlock(&inode_hash_lock);
 1320                 wait_on_inode(old);
 1321                 if (unlikely(!inode_unhashed(old))) {
 1322                         iput(old);
 1323                         return -EBUSY;
 1324                 }
 1325                 iput(old);
 1326         }
 1327 }
 1328 EXPORT_SYMBOL(insert_inode_locked);
 1329 
 1330 int insert_inode_locked4(struct inode *inode, unsigned long hashval,
 1331                 int (*test)(struct inode *, void *), void *data)
 1332 {
 1333         struct super_block *sb = inode->i_sb;
 1334         struct hlist_head *head = inode_hashtable + hash(sb, hashval);
 1335 
 1336         while (1) {
 1337                 struct hlist_node *node;
 1338                 struct inode *old = NULL;
 1339 
 1340                 spin_lock(&inode_hash_lock);
 1341                 hlist_for_each_entry(old, node, head, i_hash) {
 1342                         if (old->i_sb != sb)
 1343                                 continue;
 1344                         if (!test(old, data))
 1345                                 continue;
 1346                         spin_lock(&old->i_lock);
 1347                         if (old->i_state & (I_FREEING|I_WILL_FREE)) {
 1348                                 spin_unlock(&old->i_lock);
 1349                                 continue;
 1350                         }
 1351                         break;
 1352                 }
 1353                 if (likely(!node)) {
 1354                         spin_lock(&inode->i_lock);
 1355                         inode->i_state |= I_NEW;
 1356                         hlist_add_head(&inode->i_hash, head);
 1357                         spin_unlock(&inode->i_lock);
 1358                         spin_unlock(&inode_hash_lock);
 1359                         return 0;
 1360                 }
 1361                 __iget(old);
 1362                 spin_unlock(&old->i_lock);
 1363                 spin_unlock(&inode_hash_lock);
 1364                 wait_on_inode(old);
 1365                 if (unlikely(!inode_unhashed(old))) {
 1366                         iput(old);
 1367                         return -EBUSY;
 1368                 }
 1369                 iput(old);
 1370         }
 1371 }
 1372 EXPORT_SYMBOL(insert_inode_locked4);
 1373 
 1374 
 1375 int generic_delete_inode(struct inode *inode)
 1376 {
 1377         return 1;
 1378 }
 1379 EXPORT_SYMBOL(generic_delete_inode);
 1380 
 1381 /*
 1382  * Called when we're dropping the last reference
 1383  * to an inode.
 1384  *
 1385  * Call the FS "drop_inode()" function, defaulting to
 1386  * the legacy UNIX filesystem behaviour.  If it tells
 1387  * us to evict inode, do so.  Otherwise, retain inode
 1388  * in cache if fs is alive, sync and evict if fs is
 1389  * shutting down.
 1390  */
 1391 static void iput_final(struct inode *inode)
 1392 {
 1393         struct super_block *sb = inode->i_sb;
 1394         const struct super_operations *op = inode->i_sb->s_op;
 1395         int drop;
 1396 
 1397         WARN_ON(inode->i_state & I_NEW);
 1398 
 1399         if (op->drop_inode)
 1400                 drop = op->drop_inode(inode);
 1401         else
 1402                 drop = generic_drop_inode(inode);
 1403 
 1404         if (!drop && (sb->s_flags & MS_ACTIVE)) {
 1405                 inode->i_state |= I_REFERENCED;
 1406                 inode_add_lru(inode);
 1407                 spin_unlock(&inode->i_lock);
 1408                 return;
 1409         }
 1410 
 1411         if (!drop) {
 1412                 inode->i_state |= I_WILL_FREE;
 1413                 spin_unlock(&inode->i_lock);
 1414                 write_inode_now(inode, 1);
 1415                 spin_lock(&inode->i_lock);
 1416                 WARN_ON(inode->i_state & I_NEW);
 1417                 inode->i_state &= ~I_WILL_FREE;
 1418         }
 1419 
 1420         inode->i_state |= I_FREEING;
 1421         if (!list_empty(&inode->i_lru))
 1422                 inode_lru_list_del(inode);
 1423         spin_unlock(&inode->i_lock);
 1424 
 1425         evict(inode);
 1426 }
 1427 
 1428 /**
 1429  *      iput    - put an inode
 1430  *      @inode: inode to put
 1431  *
 1432  *      Puts an inode, dropping its usage count. If the inode use count hits
 1433  *      zero, the inode is then freed and may also be destroyed.
 1434  *
 1435  *      Consequently, iput() can sleep.
 1436  */
 1437 void iput(struct inode *inode)
 1438 {
 1439         if (inode) {
 1440                 BUG_ON(inode->i_state & I_CLEAR);
 1441 
 1442                 if (atomic_dec_and_lock(&inode->i_count, &inode->i_lock))
 1443                         iput_final(inode);
 1444         }
 1445 }
 1446 EXPORT_SYMBOL(iput);
 1447 
 1448 /**
 1449  *      bmap    - find a block number in a file
 1450  *      @inode: inode of file
 1451  *      @block: block to find
 1452  *
 1453  *      Returns the block number on the device holding the inode that
 1454  *      is the disk block number for the block of the file requested.
 1455  *      That is, asked for block 4 of inode 1 the function will return the
 1456  *      disk block relative to the disk start that holds that block of the
 1457  *      file.
 1458  */
 1459 sector_t bmap(struct inode *inode, sector_t block)
 1460 {
 1461         sector_t res = 0;
 1462         if (inode->i_mapping->a_ops->bmap)
 1463                 res = inode->i_mapping->a_ops->bmap(inode->i_mapping, block);
 1464         return res;
 1465 }
 1466 EXPORT_SYMBOL(bmap);
 1467 
 1468 /*
 1469  * With relative atime, only update atime if the previous atime is
 1470  * earlier than either the ctime or mtime or if at least a day has
 1471  * passed since the last atime update.
 1472  */
 1473 static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
 1474                              struct timespec now)
 1475 {
 1476 
 1477         if (!(mnt->mnt_flags & MNT_RELATIME))
 1478                 return 1;
 1479         /*
 1480          * Is mtime younger than atime? If yes, update atime:
 1481          */
 1482         if (timespec_compare(&inode->i_mtime, &inode->i_atime) >= 0)
 1483                 return 1;
 1484         /*
 1485          * Is ctime younger than atime? If yes, update atime:
 1486          */
 1487         if (timespec_compare(&inode->i_ctime, &inode->i_atime) >= 0)
 1488                 return 1;
 1489 
 1490         /*
 1491          * Is the previous atime value older than a day? If yes,
 1492          * update atime:
 1493          */
 1494         if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= 24*60*60)
 1495                 return 1;
 1496         /*
 1497          * Good, we can skip the atime update:
 1498          */
 1499         return 0;
 1500 }
 1501 
 1502 /*
 1503  * This does the actual work of updating an inodes time or version.  Must have
 1504  * had called mnt_want_write() before calling this.
 1505  */
 1506 static int update_time(struct inode *inode, struct timespec *time, int flags)
 1507 {
 1508         if (inode->i_op->update_time)
 1509                 return inode->i_op->update_time(inode, time, flags);
 1510 
 1511         if (flags & S_ATIME)
 1512                 inode->i_atime = *time;
 1513         if (flags & S_VERSION)
 1514                 inode_inc_iversion(inode);
 1515         if (flags & S_CTIME)
 1516                 inode->i_ctime = *time;
 1517         if (flags & S_MTIME)
 1518                 inode->i_mtime = *time;
 1519         mark_inode_dirty_sync(inode);
 1520         return 0;
 1521 }
 1522 
 1523 /**
 1524  *      touch_atime     -       update the access time
 1525  *      @path: the &struct path to update
 1526  *
 1527  *      Update the accessed time on an inode and mark it for writeback.
 1528  *      This function automatically handles read only file systems and media,
 1529  *      as well as the "noatime" flag and inode specific "noatime" markers.
 1530  */
 1531 void touch_atime(struct path *path)
 1532 {
 1533         struct vfsmount *mnt = path->mnt;
 1534         struct inode *inode = path->dentry->d_inode;
 1535         struct timespec now;
 1536 
 1537         if (inode->i_flags & S_NOATIME)
 1538                 return;
 1539         if (IS_NOATIME(inode))
 1540                 return;
 1541         if ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode))
 1542                 return;
 1543 
 1544         if (mnt->mnt_flags & MNT_NOATIME)
 1545                 return;
 1546         if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
 1547                 return;
 1548 
 1549         now = current_fs_time(inode->i_sb);
 1550 
 1551         if (!relatime_need_update(mnt, inode, now))
 1552                 return;
 1553 
 1554         if (timespec_equal(&inode->i_atime, &now))
 1555                 return;
 1556 
 1557         if (!sb_start_write_trylock(inode->i_sb))
 1558                 return;
 1559 
 1560         if (__mnt_want_write(mnt))
 1561                 goto skip_update;
 1562         /*
 1563          * File systems can error out when updating inodes if they need to
 1564          * allocate new space to modify an inode (such is the case for
 1565          * Btrfs), but since we touch atime while walking down the path we
 1566          * really don't care if we failed to update the atime of the file,
 1567          * so just ignore the return value.
 1568          * We may also fail on filesystems that have the ability to make parts
 1569          * of the fs read only, e.g. subvolumes in Btrfs.
 1570          */
 1571         update_time(inode, &now, S_ATIME);
 1572         __mnt_drop_write(mnt);
 1573 skip_update:
 1574         sb_end_write(inode->i_sb);
 1575 }
 1576 EXPORT_SYMBOL(touch_atime);
 1577 
 1578 /*
 1579  * The logic we want is
 1580  *
 1581  *      if suid or (sgid and xgrp)
 1582  *              remove privs
 1583  */
 1584 int should_remove_suid(struct dentry *dentry)
 1585 {
 1586         umode_t mode = dentry->d_inode->i_mode;
 1587         int kill = 0;
 1588 
 1589         /* suid always must be killed */
 1590         if (unlikely(mode & S_ISUID))
 1591                 kill = ATTR_KILL_SUID;
 1592 
 1593         /*
 1594          * sgid without any exec bits is just a mandatory locking mark; leave
 1595          * it alone.  If some exec bits are set, it's a real sgid; kill it.
 1596          */
 1597         if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
 1598                 kill |= ATTR_KILL_SGID;
 1599 
 1600         if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
 1601                 return kill;
 1602 
 1603         return 0;
 1604 }
 1605 EXPORT_SYMBOL(should_remove_suid);
 1606 
 1607 static int __remove_suid(struct dentry *dentry, int kill)
 1608 {
 1609         struct iattr newattrs;
 1610 
 1611         newattrs.ia_valid = ATTR_FORCE | kill;
 1612         return notify_change(dentry, &newattrs);
 1613 }
 1614 
 1615 int file_remove_suid(struct file *file)
 1616 {
 1617         struct dentry *dentry = file->f_path.dentry;
 1618         struct inode *inode = dentry->d_inode;
 1619         int killsuid;
 1620         int killpriv;
 1621         int error = 0;
 1622 
 1623         /* Fast path for nothing security related */
 1624         if (IS_NOSEC(inode))
 1625                 return 0;
 1626 
 1627         killsuid = should_remove_suid(dentry);
 1628         killpriv = security_inode_need_killpriv(dentry);
 1629 
 1630         if (killpriv < 0)
 1631                 return killpriv;
 1632         if (killpriv)
 1633                 error = security_inode_killpriv(dentry);
 1634         if (!error && killsuid)
 1635                 error = __remove_suid(dentry, killsuid);
 1636         if (!error && (inode->i_sb->s_flags & MS_NOSEC))
 1637                 inode->i_flags |= S_NOSEC;
 1638 
 1639         return error;
 1640 }
 1641 EXPORT_SYMBOL(file_remove_suid);
 1642 
 1643 /**
 1644  *      file_update_time        -       update mtime and ctime time
 1645  *      @file: file accessed
 1646  *
 1647  *      Update the mtime and ctime members of an inode and mark the inode
 1648  *      for writeback.  Note that this function is meant exclusively for
 1649  *      usage in the file write path of filesystems, and filesystems may
 1650  *      choose to explicitly ignore update via this function with the
 1651  *      S_NOCMTIME inode flag, e.g. for network filesystem where these
 1652  *      timestamps are handled by the server.  This can return an error for
 1653  *      file systems who need to allocate space in order to update an inode.
 1654  */
 1655 
 1656 int file_update_time(struct file *file)
 1657 {
 1658         struct inode *inode = file->f_path.dentry->d_inode;
 1659         struct timespec now;
 1660         int sync_it = 0;
 1661         int ret;
 1662 
 1663         /* First try to exhaust all avenues to not sync */
 1664         if (IS_NOCMTIME(inode))
 1665                 return 0;
 1666 
 1667         now = current_fs_time(inode->i_sb);
 1668         if (!timespec_equal(&inode->i_mtime, &now))
 1669                 sync_it = S_MTIME;
 1670 
 1671         if (!timespec_equal(&inode->i_ctime, &now))
 1672                 sync_it |= S_CTIME;
 1673 
 1674         if (IS_I_VERSION(inode))
 1675                 sync_it |= S_VERSION;
 1676 
 1677         if (!sync_it)
 1678                 return 0;
 1679 
 1680         /* Finally allowed to write? Takes lock. */
 1681         if (__mnt_want_write_file(file))
 1682                 return 0;
 1683 
 1684         ret = update_time(inode, &now, sync_it);
 1685         __mnt_drop_write_file(file);
 1686 
 1687         return ret;
 1688 }
 1689 EXPORT_SYMBOL(file_update_time);
 1690 
 1691 int inode_needs_sync(struct inode *inode)
 1692 {
 1693         if (IS_SYNC(inode))
 1694                 return 1;
 1695         if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
 1696                 return 1;
 1697         return 0;
 1698 }
 1699 EXPORT_SYMBOL(inode_needs_sync);
 1700 
 1701 int inode_wait(void *word)
 1702 {
 1703         schedule();
 1704         return 0;
 1705 }
 1706 EXPORT_SYMBOL(inode_wait);
 1707 
 1708 /*
 1709  * If we try to find an inode in the inode hash while it is being
 1710  * deleted, we have to wait until the filesystem completes its
 1711  * deletion before reporting that it isn't found.  This function waits
 1712  * until the deletion _might_ have completed.  Callers are responsible
 1713  * to recheck inode state.
 1714  *
 1715  * It doesn't matter if I_NEW is not set initially, a call to
 1716  * wake_up_bit(&inode->i_state, __I_NEW) after removing from the hash list
 1717  * will DTRT.
 1718  */
 1719 static void __wait_on_freeing_inode(struct inode *inode)
 1720 {
 1721         wait_queue_head_t *wq;
 1722         DEFINE_WAIT_BIT(wait, &inode->i_state, __I_NEW);
 1723         wq = bit_waitqueue(&inode->i_state, __I_NEW);
 1724         prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
 1725         spin_unlock(&inode->i_lock);
 1726         spin_unlock(&inode_hash_lock);
 1727         schedule();
 1728         finish_wait(wq, &wait.wait);
 1729         spin_lock(&inode_hash_lock);
 1730 }
 1731 
 1732 static __initdata unsigned long ihash_entries;
 1733 static int __init set_ihash_entries(char *str)
 1734 {
 1735         if (!str)
 1736                 return 0;
 1737         ihash_entries = simple_strtoul(str, &str, 0);
 1738         return 1;
 1739 }
 1740 __setup("ihash_entries=", set_ihash_entries);
 1741 
 1742 /*
 1743  * Initialize the waitqueues and inode hash table.
 1744  */
 1745 void __init inode_init_early(void)
 1746 {
 1747         unsigned int loop;
 1748 
 1749         /* If hashes are distributed across NUMA nodes, defer
 1750          * hash allocation until vmalloc space is available.
 1751          */
 1752         if (hashdist)
 1753                 return;
 1754 
 1755         inode_hashtable =
 1756                 alloc_large_system_hash("Inode-cache",
 1757                                         sizeof(struct hlist_head),
 1758                                         ihash_entries,
 1759                                         14,
 1760                                         HASH_EARLY,
 1761                                         &i_hash_shift,
 1762                                         &i_hash_mask,
 1763                                         0,
 1764                                         0);
 1765 
 1766         for (loop = 0; loop < (1U << i_hash_shift); loop++)
 1767                 INIT_HLIST_HEAD(&inode_hashtable[loop]);
 1768 }
 1769 
 1770 void __init inode_init(void)
 1771 {
 1772         unsigned int loop;
 1773 
 1774         /* inode slab cache */
 1775         inode_cachep = kmem_cache_create("inode_cache",
 1776                                          sizeof(struct inode),
 1777                                          0,
 1778                                          (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
 1779                                          SLAB_MEM_SPREAD),
 1780                                          init_once);
 1781 
 1782         /* Hash may have been set up in inode_init_early */
 1783         if (!hashdist)
 1784                 return;
 1785 
 1786         inode_hashtable =
 1787                 alloc_large_system_hash("Inode-cache",
 1788                                         sizeof(struct hlist_head),
 1789                                         ihash_entries,
 1790                                         14,
 1791                                         0,
 1792                                         &i_hash_shift,
 1793                                         &i_hash_mask,
 1794                                         0,
 1795                                         0);
 1796 
 1797         for (loop = 0; loop < (1U << i_hash_shift); loop++)
 1798                 INIT_HLIST_HEAD(&inode_hashtable[loop]);
 1799 }
 1800 
 1801 void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
 1802 {
 1803         inode->i_mode = mode;
 1804         if (S_ISCHR(mode)) {
 1805                 inode->i_fop = &def_chr_fops;
 1806                 inode->i_rdev = rdev;
 1807         } else if (S_ISBLK(mode)) {
 1808                 inode->i_fop = &def_blk_fops;
 1809                 inode->i_rdev = rdev;
 1810         } else if (S_ISFIFO(mode))
 1811                 inode->i_fop = &def_fifo_fops;
 1812         else if (S_ISSOCK(mode))
 1813                 inode->i_fop = &bad_sock_fops;
 1814         else
 1815                 printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o) for"
 1816                                   " inode %s:%lu\n", mode, inode->i_sb->s_id,
 1817                                   inode->i_ino);
 1818 }
 1819 EXPORT_SYMBOL(init_special_inode);
 1820 
 1821 /**
 1822  * inode_init_owner - Init uid,gid,mode for new inode according to posix standards
 1823  * @inode: New inode
 1824  * @dir: Directory inode
 1825  * @mode: mode of the new inode
 1826  */
 1827 void inode_init_owner(struct inode *inode, const struct inode *dir,
 1828                         umode_t mode)
 1829 {
 1830         inode->i_uid = current_fsuid();
 1831         if (dir && dir->i_mode & S_ISGID) {
 1832                 inode->i_gid = dir->i_gid;
 1833                 if (S_ISDIR(mode))
 1834                         mode |= S_ISGID;
 1835         } else
 1836                 inode->i_gid = current_fsgid();
 1837         inode->i_mode = mode;
 1838 }
 1839 EXPORT_SYMBOL(inode_init_owner);
 1840 
 1841 /**
 1842  * inode_owner_or_capable - check current task permissions to inode
 1843  * @inode: inode being checked
 1844  *
 1845  * Return true if current either has CAP_FOWNER to the inode, or
 1846  * owns the file.
 1847  */
 1848 bool inode_owner_or_capable(const struct inode *inode)
 1849 {
 1850         if (uid_eq(current_fsuid(), inode->i_uid))
 1851                 return true;
 1852         if (inode_capable(inode, CAP_FOWNER))
 1853                 return true;
 1854         return false;
 1855 }
 1856 EXPORT_SYMBOL(inode_owner_or_capable);
 1857 
 1858 /*
 1859  * Direct i/o helper functions
 1860  */
 1861 static void __inode_dio_wait(struct inode *inode)
 1862 {
 1863         wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
 1864         DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);
 1865 
 1866         do {
 1867                 prepare_to_wait(wq, &q.wait, TASK_UNINTERRUPTIBLE);
 1868                 if (atomic_read(&inode->i_dio_count))
 1869                         schedule();
 1870         } while (atomic_read(&inode->i_dio_count));
 1871         finish_wait(wq, &q.wait);
 1872 }
 1873 
 1874 /**
 1875  * inode_dio_wait - wait for outstanding DIO requests to finish
 1876  * @inode: inode to wait for
 1877  *
 1878  * Waits for all pending direct I/O requests to finish so that we can
 1879  * proceed with a truncate or equivalent operation.
 1880  *
 1881  * Must be called under a lock that serializes taking new references
 1882  * to i_dio_count, usually by inode->i_mutex.
 1883  */
 1884 void inode_dio_wait(struct inode *inode)
 1885 {
 1886         if (atomic_read(&inode->i_dio_count))
 1887                 __inode_dio_wait(inode);
 1888 }
 1889 EXPORT_SYMBOL(inode_dio_wait);
 1890 
 1891 /*
 1892  * inode_dio_done - signal finish of a direct I/O requests
 1893  * @inode: inode the direct I/O happens on
 1894  *
 1895  * This is called once we've finished processing a direct I/O request,
 1896  * and is used to wake up callers waiting for direct I/O to be quiesced.
 1897  */
 1898 void inode_dio_done(struct inode *inode)
 1899 {
 1900         if (atomic_dec_and_test(&inode->i_dio_count))
 1901                 wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
 1902 }
 1903 EXPORT_SYMBOL(inode_dio_done);

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