xfs: store xfs_mount in the buftarg instead of in the xfs_buf

Each buffer contains both a buftarg pointer and a mount pointer. If
we add a mount pointer into the buftarg, we can avoid needing the
b_mount field in every buffer and grab it from the buftarg when
needed instead. This shrinks the xfs_buf by 8 bytes.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>

5 files changed, 20 insertions, 21 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 22c7bff77ad2..d6928970097f 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -894,7 +894,7 @@ xfs_buf_lock(
         trace_xfs_buf_lock(bp, _RET_IP_);
 
         if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
-                xfs_log_force(bp->b_mount, 0);
+                xfs_log_force(bp->b_target->bt_mount, 0);
         if (atomic_read(&bp->b_io_remaining))
                 blk_run_address_space(bp->b_target->bt_mapping);
         down(&bp->b_sema);
@@ -1017,7 +1017,6 @@ xfs_bwrite(
 {
         int                     error;
 
-        bp->b_mount = mp;
         bp->b_flags |= XBF_WRITE;
         bp->b_flags &= ~(XBF_ASYNC | XBF_READ);
 
@@ -1038,8 +1037,6 @@ xfs_bdwrite(
 {
         trace_xfs_buf_bdwrite(bp, _RET_IP_);
 
-        bp->b_mount = mp;
-
         bp->b_flags &= ~XBF_READ;
         bp->b_flags |= (XBF_DELWRI | XBF_ASYNC);
 
@@ -1128,7 +1125,7 @@ int
 xfs_bdstrat_cb(
         struct xfs_buf  *bp)
 {
-        if (XFS_FORCED_SHUTDOWN(bp->b_mount)) {
+        if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
                 trace_xfs_bdstrat_shut(bp, _RET_IP_);
                 /*
                  * Metadata write that didn't get logged but
@@ -1644,6 +1641,7 @@ out_error:
 
 xfs_buftarg_t *
 xfs_alloc_buftarg(
+        struct xfs_mount        *mp,
         struct block_device     *bdev,
         int                     external,
         const char              *fsname)
@@ -1652,6 +1650,7 @@ xfs_alloc_buftarg(
 
         btp = kmem_zalloc(sizeof(*btp), KM_SLEEP);
 
+        btp->bt_mount = mp;
         btp->bt_dev =  bdev->bd_dev;
         btp->bt_bdev = bdev;
         if (xfs_setsize_buftarg_early(btp, bdev))
diff --git a/fs/xfs/linux-2.6/xfs_buf.h b/fs/xfs/linux-2.6/xfs_buf.h
index 57eedc750ee6..def2cea2b4d6 100644
--- a/fs/xfs/linux-2.6/xfs_buf.h
+++ b/fs/xfs/linux-2.6/xfs_buf.h
@@ -132,6 +132,7 @@ typedef struct xfs_buftarg {
         dev_t                   bt_dev;
         struct block_device     *bt_bdev;
         struct address_space    *bt_mapping;
+        struct xfs_mount        *bt_mount;
         unsigned int            bt_bsize;
         unsigned int            bt_sshift;
         size_t                  bt_smask;
@@ -189,7 +190,6 @@ typedef struct xfs_buf {
         struct completion       b_iowait;       /* queue for I/O waiters */
         void                    *b_fspriv;
         void                    *b_fspriv2;
-        struct xfs_mount        *b_mount;
         unsigned short          b_error;        /* error code on I/O */
         unsigned int            b_page_count;   /* size of page array */
         unsigned int            b_offset;       /* page offset in first page */
@@ -377,7 +377,8 @@ static inline void xfs_buf_relse(xfs_buf_t *bp)
 /*
  *      Handling of buftargs.
  */
-extern xfs_buftarg_t *xfs_alloc_buftarg(struct block_device *, int, const char *);
+extern xfs_buftarg_t *xfs_alloc_buftarg(struct xfs_mount *,
+                        struct block_device *, int, const char *);
 extern void xfs_free_buftarg(struct xfs_mount *, struct xfs_buftarg *);
 extern void xfs_wait_buftarg(xfs_buftarg_t *);
 extern int xfs_setsize_buftarg(xfs_buftarg_t *, unsigned int, unsigned int);
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 83154c0a3175..4759be4daa26 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -758,18 +758,20 @@ xfs_open_devices(
          * Setup xfs_mount buffer target pointers
          */
         error = ENOMEM;
-        mp->m_ddev_targp = xfs_alloc_buftarg(ddev, 0, mp->m_fsname);
+        mp->m_ddev_targp = xfs_alloc_buftarg(mp, ddev, 0, mp->m_fsname);
         if (!mp->m_ddev_targp)
                 goto out_close_rtdev;
 
         if (rtdev) {
-                mp->m_rtdev_targp = xfs_alloc_buftarg(rtdev, 1, mp->m_fsname);
+                mp->m_rtdev_targp = xfs_alloc_buftarg(mp, rtdev, 1,
+                                                        mp->m_fsname);
                 if (!mp->m_rtdev_targp)
                         goto out_free_ddev_targ;
         }
 
         if (logdev && logdev != ddev) {
-                mp->m_logdev_targp = xfs_alloc_buftarg(logdev, 1, mp->m_fsname);
+                mp->m_logdev_targp = xfs_alloc_buftarg(mp, logdev, 1,
+                                                        mp->m_fsname);
                 if (!mp->m_logdev_targp)
                         goto out_free_rtdev_targ;
         } else {
diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 1b09d7a280df..ee7557611b6e 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -692,8 +692,7 @@ xfs_buf_item_init(
          * the first.  If we do already have one, there is
          * nothing to do here so return.
          */
-        if (bp->b_mount != mp)
-                bp->b_mount = mp;
+        ASSERT(bp->b_target->bt_mount == mp);
         if (XFS_BUF_FSPRIVATE(bp, void *) != NULL) {
                 lip = XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *);
                 if (lip->li_type == XFS_LI_BUF) {
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 3d887542b037..351d71117f16 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -322,10 +322,11 @@ xlog_recover_iodone(
                  * this during recovery. One strike!
                  */
                 xfs_ioerror_alert("xlog_recover_iodone",
-                                  bp->b_mount, bp, XFS_BUF_ADDR(bp));
-                xfs_force_shutdown(bp->b_mount, SHUTDOWN_META_IO_ERROR);
+                                        bp->b_target->bt_mount, bp,
+                                        XFS_BUF_ADDR(bp));
+                xfs_force_shutdown(bp->b_target->bt_mount,
+                                        SHUTDOWN_META_IO_ERROR);
         }
-        bp->b_mount = NULL;
         XFS_BUF_CLR_IODONE_FUNC(bp);
         xfs_biodone(bp);
 }
@@ -2276,8 +2277,7 @@ xlog_recover_do_buffer_trans(
                 XFS_BUF_STALE(bp);
                 error = xfs_bwrite(mp, bp);
         } else {
-                ASSERT(bp->b_mount == NULL || bp->b_mount == mp);
-                bp->b_mount = mp;
+                ASSERT(bp->b_target->bt_mount == mp);
                 XFS_BUF_SET_IODONE_FUNC(bp, xlog_recover_iodone);
                 xfs_bdwrite(mp, bp);
         }
@@ -2541,8 +2541,7 @@ xlog_recover_do_inode_trans(
         }
 
 write_inode_buffer:
-        ASSERT(bp->b_mount == NULL || bp->b_mount == mp);
-        bp->b_mount = mp;
+        ASSERT(bp->b_target->bt_mount == mp);
         XFS_BUF_SET_IODONE_FUNC(bp, xlog_recover_iodone);
         xfs_bdwrite(mp, bp);
 error:
@@ -2679,8 +2678,7 @@ xlog_recover_do_dquot_trans(
         memcpy(ddq, recddq, item->ri_buf[1].i_len);
 
         ASSERT(dq_f->qlf_size == 2);
-        ASSERT(bp->b_mount == NULL || bp->b_mount == mp);
-        bp->b_mount = mp;
+        ASSERT(bp->b_target->bt_mount == mp);
         XFS_BUF_SET_IODONE_FUNC(bp, xlog_recover_iodone);
         xfs_bdwrite(mp, bp);