FreeBSD/Linux Kernel Cross Reference
sys/sys/buf.h

     /*
      * Copyright (c) 1982, 1986, 1989, 1993
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * All or some portions of this file are derived from material licensed
      * to the University of California by American Telephone and Telegraph
      * Co. or Unix System Laboratories, Inc. and are reproduced herein with
      * the permission of UNIX System Laboratories, Inc.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)buf.h       8.9 (Berkeley) 3/30/95
     * $FreeBSD$
     */
    
    #ifndef _SYS_BUF_H_
    #define _SYS_BUF_H_
    
    #include <sys/queue.h>
    #include <sys/lock.h>
    
    struct buf;
    struct mount;
    struct vnode;
    
    /*
     * To avoid including <ufs/ffs/softdep.h> 
     */   
    LIST_HEAD(workhead, worklist);
    /*
     * These are currently used only by the soft dependency code, hence
     * are stored once in a global variable. If other subsystems wanted
     * to use these hooks, a pointer to a set of bio_ops could be added
     * to each buffer.
     */
    extern struct bio_ops {
            void    (*io_start) __P((struct buf *));
            void    (*io_complete) __P((struct buf *));
            void    (*io_deallocate) __P((struct buf *));
            int     (*io_fsync) __P((struct vnode *));
            int     (*io_sync) __P((struct mount *));
            void    (*io_movedeps) __P((struct buf *, struct buf *));
            int     (*io_countdeps) __P((struct buf *, int));
    } bioops;
    
    struct iodone_chain {
            long    ic_prev_flags;
            void    (*ic_prev_iodone) __P((struct buf *));
            void    *ic_prev_iodone_chain;
            struct {
                    long    ia_long;
                    void    *ia_ptr;
            }       ic_args[5];
    };
    
    /*
     * The buffer header describes an I/O operation in the kernel.
     *
     * NOTES:
     *      b_bufsize, b_bcount.  b_bufsize is the allocation size of the
     *      buffer, either DEV_BSIZE or PAGE_SIZE aligned.  b_bcount is the
     *      originally requested buffer size and can serve as a bounds check
     *      against EOF.  For most, but not all uses, b_bcount == b_bufsize.
     *
     *      b_dirtyoff, b_dirtyend.  Buffers support piecemeal, unaligned
     *      ranges of dirty data that need to be written to backing store.
     *      The range is typically clipped at b_bcount ( not b_bufsize ).
     *
     *      b_resid.  Number of bytes remaining in I/O.  After an I/O operation
     *      completes, b_resid is usually 0 indicating 100% success.
     */
    struct buf {
            LIST_ENTRY(buf) b_hash;         /* Hash chain. */
           TAILQ_ENTRY(buf) b_vnbufs;      /* Buffer's associated vnode. */
           TAILQ_ENTRY(buf) b_freelist;    /* Free list position if not active. */
           TAILQ_ENTRY(buf) b_act;         /* Device driver queue when active. *new* */
           long    b_flags;                /* B_* flags. */
           unsigned short b_qindex;        /* buffer queue index */
           unsigned char b_xflags;         /* extra flags */
           struct lock b_lock;             /* Buffer lock */
           int     b_error;                /* Errno value. */
           long    b_bufsize;              /* Allocated buffer size. */
           long    b_runningbufspace;      /* when I/O is running, pipelining */
           long    b_bcount;               /* Valid bytes in buffer. */
           long    b_resid;                /* Remaining I/O. */
           dev_t   b_dev;                  /* Device associated with buffer. */
           caddr_t b_data;                 /* Memory, superblocks, indirect etc. */
           caddr_t b_kvabase;              /* base kva for buffer */
           int     b_kvasize;              /* size of kva for buffer */
           daddr_t b_lblkno;               /* Logical block number. */
           daddr_t b_blkno;                /* Underlying physical block number. */
           off_t   b_offset;               /* Offset into file */
                                           /* Function to call upon completion. */
           void    (*b_iodone) __P((struct buf *));
                                           /* For nested b_iodone's. */
           struct  iodone_chain *b_iodone_chain;
           struct  vnode *b_vp;            /* Device vnode. */
           int     b_dirtyoff;             /* Offset in buffer of dirty region. */
           int     b_dirtyend;             /* Offset of end of dirty region. */
           struct  ucred *b_rcred;         /* Read credentials reference. */
           struct  ucred *b_wcred;         /* Write credentials reference. */
           daddr_t b_pblkno;               /* physical block number */
           void    *b_saveaddr;            /* Original b_addr for physio. */
           void    *b_driver1;             /* for private use by the driver */
           void    *b_driver2;             /* for private use by the driver */
           void    *b_caller1;             /* for private use by the caller */
           void    *b_caller2;             /* for private use by the caller */
           union   pager_info {
                   void    *pg_spc;
                   int     pg_reqpage;
           } b_pager;
           union   cluster_info {
                   TAILQ_HEAD(cluster_list_head, buf) cluster_head;
                   TAILQ_ENTRY(buf) cluster_entry;
           } b_cluster;
           struct  vm_page *b_pages[btoc(MAXPHYS)];
           int             b_npages;
           struct  workhead b_dep;         /* List of filesystem dependencies. */
           struct chain_info {             /* buffer chaining */
                   struct buf *parent;
                   int count;
           } b_chain;
   };
   
   #define b_spc   b_pager.pg_spc
   
   /*
    * These flags are kept in b_flags.
    *
    * Notes:
    *
    *      B_ASYNC         VOP calls on bp's are usually async whether or not
    *                      B_ASYNC is set, but some subsystems, such as NFS, like 
    *                      to know what is best for the caller so they can
    *                      optimize the I/O.
    *
    *      B_PAGING        Indicates that bp is being used by the paging system or
    *                      some paging system and that the bp is not linked into
    *                      the b_vp's clean/dirty linked lists or ref counts.
    *                      Buffer vp reassignments are illegal in this case.
    *
    *      B_CACHE         This may only be set if the buffer is entirely valid.
    *                      The situation where B_DELWRI is set and B_CACHE is
    *                      clear MUST be committed to disk by getblk() so 
    *                      B_DELWRI can also be cleared.  See the comments for
    *                      getblk() in kern/vfs_bio.c.  If B_CACHE is clear,
    *                      the caller is expected to clear B_ERROR|B_INVAL,
    *                      set B_READ, and initiate an I/O.
    *
    *                      The 'entire buffer' is defined to be the range from
    *                      0 through b_bcount.
    *
    *      B_MALLOC        Request that the buffer be allocated from the malloc
    *                      pool, DEV_BSIZE aligned instead of PAGE_SIZE aligned.
    *
    *      B_CLUSTEROK     This flag is typically set for B_DELWRI buffers
    *                      by filesystems that allow clustering when the buffer
    *                      is fully dirty and indicates that it may be clustered
    *                      with other adjacent dirty buffers.  Note the clustering
    *                      may not be used with the stage 1 data write under NFS
    *                      but may be used for the commit rpc portion.
    *
    *      B_VMIO          Indicates that the buffer is tied into an VM object.
    *                      The buffer's data is always PAGE_SIZE aligned even
    *                      if b_bufsize and b_bcount are not.  ( b_bufsize is 
    *                      always at least DEV_BSIZE aligned, though ).
    *      
    *      B_DIRECT        Hint that we should attempt to completely free
    *                      the pages underlying the buffer.   B_DIRECT is 
    *                      sticky until the buffer is released and typically
    *                      only has an effect when B_RELBUF is also set.
    *
    *      B_NOWDRAIN      This flag should be set when a device (like VN)
    *                      does a turn-around VOP_WRITE from its strategy
    *                      routine.  This flag prevents bwrite() from blocking
    *                      in wdrain, avoiding a deadlock situation.
    */
   
   #define B_AGE           0x00000001      /* Move to age queue when I/O done. */
   #define B_NEEDCOMMIT    0x00000002      /* Append-write in progress. */
   #define B_ASYNC         0x00000004      /* Start I/O, do not wait. */
   #define B_DIRECT        0x00000008      /* direct I/O flag (pls free vmio) */
   #define B_DEFERRED      0x00000010      /* Skipped over for cleaning */
   #define B_CACHE         0x00000020      /* Bread found us in the cache. */
   #define B_CALL          0x00000040      /* Call b_iodone from biodone. */
   #define B_DELWRI        0x00000080      /* Delay I/O until buffer reused. */
   #define B_FREEBUF       0x00000100      /* Instruct driver: free blocks */
   #define B_DONE          0x00000200      /* I/O completed. */
   #define B_EINTR         0x00000400      /* I/O was interrupted */
   #define B_ERROR         0x00000800      /* I/O error occurred. */
   #define B_SCANNED       0x00001000      /* VOP_FSYNC funcs mark written bufs */
   #define B_INVAL         0x00002000      /* Does not contain valid info. */
   #define B_LOCKED        0x00004000      /* Locked in core (not reusable). */
   #define B_NOCACHE       0x00008000      /* Do not cache block after use. */
   #define B_MALLOC        0x00010000      /* malloced b_data */
   #define B_CLUSTEROK     0x00020000      /* Pagein op, so swap() can count it. */
   #define B_PHYS          0x00040000      /* I/O to user memory. */
   #define B_RAW           0x00080000      /* Set by physio for raw transfers. */
   #define B_READ          0x00100000      /* Read buffer. */
   #define B_DIRTY         0x00200000      /* Needs writing later. */
   #define B_RELBUF        0x00400000      /* Release VMIO buffer. */
   #define B_WANT          0x00800000      /* Used by vm_pager.c */
   #define B_WRITE         0x00000000      /* Write buffer (pseudo flag). */
   #define B_WRITEINPROG   0x01000000      /* Write in progress. */
   #define B_XXX           0x02000000      /* Debugging flag. */
   #define B_PAGING        0x04000000      /* volatile paging I/O -- bypass VMIO */
   #define B_ORDERED       0x08000000      /* Must guarantee I/O ordering */
   #define B_RAM           0x10000000      /* Read ahead mark (flag) */
   #define B_VMIO          0x20000000      /* VMIO flag */
   #define B_CLUSTER       0x40000000      /* pagein op, so swap() can count it */
   #define B_NOWDRAIN      0x80000000      /* Avoid wdrain deadlock */
   
   #define PRINT_BUF_FLAGS "\2\40nowdrain\37cluster\36vmio\35ram\34ordered" \
           "\33paging\32xxx\31writeinprog\30want\27relbuf\26dirty" \
           "\25read\24raw\23phys\22clusterok\21malloc\20nocache" \
           "\17locked\16inval\15scanned\14error\13eintr\12done\11freebuf" \
           "\10delwri\7call\6cache\4direct\3async\2needcommit\1age"
   
   /*
    * These flags are kept in b_xflags.
    */
   #define BX_VNDIRTY      0x00000001      /* On vnode dirty list */
   #define BX_VNCLEAN      0x00000002      /* On vnode clean list */
   #define BX_BKGRDWRITE   0x00000004      /* Do writes in background */
   #define BX_BKGRDINPROG  0x00000008      /* Background write in progress */
   #define BX_BKGRDWAIT    0x00000010      /* Background write waiting */
   #define BX_AUTOCHAINDONE 0x00000020     /* pager I/O chain auto mode */
   
   #define NOOFFSET        (-1LL)          /* No buffer offset calculated yet */
   
   #ifdef _KERNEL
   /*
    * Buffer locking
    */
   struct simplelock buftimelock;          /* Interlock on setting prio and timo */
   extern char *buf_wmesg;                 /* Default buffer lock message */
   #define BUF_WMESG "bufwait"
   #include <sys/proc.h>                   /* XXX for curproc */
   /*
    * Initialize a lock.
    */
   #define BUF_LOCKINIT(bp) \
           lockinit(&(bp)->b_lock, PRIBIO + 4, buf_wmesg, 0, 0)
   /*
    *
    * Get a lock sleeping non-interruptably until it becomes available.
    */
   static __inline int BUF_LOCK __P((struct buf *, int));
   static __inline int
   BUF_LOCK(struct buf *bp, int locktype)
   {
           int s, ret;
   
           s = splbio();
           simple_lock(&buftimelock);
           locktype |= LK_INTERLOCK;
           bp->b_lock.lk_wmesg = buf_wmesg;
           bp->b_lock.lk_prio = PRIBIO + 4;
           /* bp->b_lock.lk_timo = 0;   not necessary */
           ret = lockmgr(&(bp)->b_lock, locktype, &buftimelock, curproc);
           splx(s);
           return ret;
   }
   /*
    * Get a lock sleeping with specified interruptably and timeout.
    */
   static __inline int BUF_TIMELOCK __P((struct buf *, int, char *, int, int));
   static __inline int
   BUF_TIMELOCK(struct buf *bp, int locktype, char *wmesg, int catch, int timo)
   {
           int s, ret;
   
           s = splbio();
           simple_lock(&buftimelock);
           locktype |= LK_INTERLOCK | LK_TIMELOCK;
           bp->b_lock.lk_wmesg = wmesg;
           bp->b_lock.lk_prio = (PRIBIO + 4) | catch;
           bp->b_lock.lk_timo = timo;
           ret = lockmgr(&(bp)->b_lock, (locktype), &buftimelock, curproc);
           splx(s);
           return ret;
   }
   /*
    * Release a lock. Only the acquiring process may free the lock unless
    * it has been handed off to biodone.
    */
   static __inline void BUF_UNLOCK __P((struct buf *));
   static __inline void
   BUF_UNLOCK(struct buf *bp)
   {
           int s;
   
           s = splbio();
           lockmgr(&(bp)->b_lock, LK_RELEASE, NULL, curproc);
           splx(s);
   }
   
   /*
    * Free a buffer lock.
    */
   #define BUF_LOCKFREE(bp)                        \
           if (BUF_REFCNT(bp) > 0)                 \
                   panic("free locked buf")
   /*
    * When initiating asynchronous I/O, change ownership of the lock to the
    * kernel. Once done, the lock may legally released by biodone. The
    * original owning process can no longer acquire it recursively, but must
    * wait until the I/O is completed and the lock has been freed by biodone.
    */
   static __inline void BUF_KERNPROC __P((struct buf *));
   static __inline void
   BUF_KERNPROC(struct buf *bp)
   {
           struct proc *p = curproc;
   
           if (p != NULL && bp->b_lock.lk_lockholder == p->p_pid)
                   p->p_locks--;
           bp->b_lock.lk_lockholder = LK_KERNPROC;
   }
   /*
    * Find out the number of references to a lock.
    */
   static __inline int BUF_REFCNT __P((struct buf *));
   static __inline int
   BUF_REFCNT(struct buf *bp)
   {
           int s, ret;
   
           s = splbio();
           ret = lockcount(&(bp)->b_lock);
           splx(s);
           return ret;
   }
   
   #endif /* _KERNEL */
   
   struct buf_queue_head {
           TAILQ_HEAD(buf_queue, buf) queue;
           daddr_t last_pblkno;
           struct  buf *insert_point;
           struct  buf *switch_point;
   };
   
   /*
    * This structure describes a clustered I/O.  It is stored in the b_saveaddr
    * field of the buffer on which I/O is done.  At I/O completion, cluster
    * callback uses the structure to parcel I/O's to individual buffers, and
    * then free's this structure.
    */
   struct cluster_save {
           long    bs_bcount;              /* Saved b_bcount. */
           long    bs_bufsize;             /* Saved b_bufsize. */
           void    *bs_saveaddr;           /* Saved b_addr. */
           int     bs_nchildren;           /* Number of associated buffers. */
           struct buf **bs_children;       /* List of associated buffers. */
   };
   
   #ifdef _KERNEL
   static __inline void bufq_init __P((struct buf_queue_head *head));
   
   static __inline void bufq_insert_tail __P((struct buf_queue_head *head,
                                              struct buf *bp));
   
   static __inline void bufq_remove __P((struct buf_queue_head *head,
                                         struct buf *bp));
   
   static __inline struct buf *bufq_first __P((struct buf_queue_head *head));
   
   static __inline void
   bufq_init(struct buf_queue_head *head)
   {
           TAILQ_INIT(&head->queue);
           head->last_pblkno = 0;
           head->insert_point = NULL;
           head->switch_point = NULL;
   }
   
   static __inline void
   bufq_insert_tail(struct buf_queue_head *head, struct buf *bp)
   {
           if ((bp->b_flags & B_ORDERED) != 0) {
                   head->insert_point = bp;
                   head->switch_point = NULL;
           }
           TAILQ_INSERT_TAIL(&head->queue, bp, b_act);
   }
   
   static __inline void
   bufq_remove(struct buf_queue_head *head, struct buf *bp)
   {
           if (bp == head->switch_point)
                   head->switch_point = TAILQ_NEXT(bp, b_act);
           if (bp == head->insert_point) {
                   head->insert_point = TAILQ_PREV(bp, buf_queue, b_act);
                   if (head->insert_point == NULL)
                           head->last_pblkno = 0;
           } else if (bp == TAILQ_FIRST(&head->queue))
                   head->last_pblkno = bp->b_pblkno;
           TAILQ_REMOVE(&head->queue, bp, b_act);
           if (TAILQ_FIRST(&head->queue) == head->switch_point)
                   head->switch_point = NULL;
   }
   
   static __inline struct buf *
   bufq_first(struct buf_queue_head *head)
   {
           return (TAILQ_FIRST(&head->queue));
   }
   
   #endif /* _KERNEL */
   
   /*
    * Definitions for the buffer free lists.
    */
   #define BUFFER_QUEUES   6       /* number of free buffer queues */
   
   #define QUEUE_NONE      0       /* on no queue */
   #define QUEUE_LOCKED    1       /* locked buffers */
   #define QUEUE_CLEAN     2       /* non-B_DELWRI buffers */
   #define QUEUE_DIRTY     3       /* B_DELWRI buffers */
   #define QUEUE_EMPTYKVA  4       /* empty buffer headers w/KVA assignment */
   #define QUEUE_EMPTY     5       /* empty buffer headers */
   
   /*
    * Zero out the buffer's data area.
    */
   #define clrbuf(bp) {                                                    \
           bzero((bp)->b_data, (u_int)(bp)->b_bcount);                     \
           (bp)->b_resid = 0;                                              \
   }
   
   /*
    * Flags to low-level bitmap allocation routines (balloc).
    *
    * Note: sequential_heuristic() in kern/vfs_vnops.c limits the count
    * to 127.
    */
   #define B_SEQMASK       0x7F000000      /* Sequential heuristic mask. */
   #define B_SEQSHIFT      24              /* Sequential heuristic shift. */
   #define B_SEQMAX        0x7F
   #define B_CLRBUF        0x01            /* Cleared invalid areas of buffer. */
   #define B_SYNC          0x02            /* Do all allocations synchronously. */
   
   #ifdef _KERNEL
   extern int      nbuf;                   /* The number of buffer headers */
   extern int      maxswzone;              /* Max KVA for swap structures */
   extern int      maxbcache;              /* Max KVA for buffer cache */
   extern int      runningbufspace;
   extern int      buf_maxio;              /* nominal maximum I/O for buffer */
   extern struct   buf *buf;               /* The buffer headers. */
   extern char     *buffers;               /* The buffer contents. */
   extern int      bufpages;               /* Number of memory pages in the buffer pool. */
   extern struct   buf *swbuf;             /* Swap I/O buffer headers. */
   extern int      nswbuf;                 /* Number of swap I/O buffer headers. */
   extern TAILQ_HEAD(swqueue, buf) bswlist;
   extern TAILQ_HEAD(bqueues, buf) bufqueues[BUFFER_QUEUES];
   
   struct uio;
   
   caddr_t bufhashinit __P((caddr_t));
   void    bufinit __P((void));
   void    bwillwrite __P((void));
   int     buf_dirty_count_severe __P((void));
   void    bremfree __P((struct buf *));
   int     bread __P((struct vnode *, daddr_t, int,
               struct ucred *, struct buf **));
   int     breadn __P((struct vnode *, daddr_t, int, daddr_t *, int *, int,
               struct ucred *, struct buf **));
   int     bwrite __P((struct buf *));
   void    bdwrite __P((struct buf *));
   void    bawrite __P((struct buf *));
   void    bdirty __P((struct buf *));
   void    bundirty __P((struct buf *));
   int     bowrite __P((struct buf *));
   void    brelse __P((struct buf *));
   void    bqrelse __P((struct buf *));
   int     vfs_bio_awrite __P((struct buf *));
   struct buf *     getpbuf __P((int *));
   struct buf *incore __P((struct vnode *, daddr_t));
   struct buf *gbincore __P((struct vnode *, daddr_t));
   int     inmem __P((struct vnode *, daddr_t));
   struct buf *getblk __P((struct vnode *, daddr_t, int, int, int));
   struct buf *geteblk __P((int));
   int     biowait __P((struct buf *));
   void    biodone __P((struct buf *));
   
   void    cluster_callback __P((struct buf *));
   int     cluster_read __P((struct vnode *, u_quad_t, daddr_t, long,
               struct ucred *, long, int, struct buf **));
   int     cluster_wbuild __P((struct vnode *, long, daddr_t, int));
   void    cluster_write __P((struct buf *, u_quad_t, int));
   int     physio __P((dev_t dev, struct uio *uio, int ioflag));
   #define physread physio
   #define physwrite physio
   void    vfs_bio_set_validclean __P((struct buf *, int base, int size));
   void    vfs_bio_clrbuf __P((struct buf *));
   void    vfs_busy_pages __P((struct buf *, int clear_modify));
   void    vfs_unbusy_pages __P((struct buf *));
   void    vwakeup __P((struct buf *));
   int     vmapbuf __P((struct buf *));
   void    vunmapbuf __P((struct buf *));
   void    relpbuf __P((struct buf *, int *));
   void    brelvp __P((struct buf *));
   void    bgetvp __P((struct vnode *, struct buf *));
   void    pbgetvp __P((struct vnode *, struct buf *));
   void    pbrelvp __P((struct buf *));
   int     allocbuf __P((struct buf *bp, int size));
   void    reassignbuf __P((struct buf *, struct vnode *));
   void    pbreassignbuf __P((struct buf *, struct vnode *));
   struct  buf *trypbuf __P((int *));
   
   #endif /* _KERNEL */
   
   #endif /* !_SYS_BUF_H_ */

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