[XFS] Make hole punching at EOF atomic.

If hole punching at EOF is done as two steps (i.e. truncate then extend)
the file is in a transient state between the two steps where an
application can see the incorrect file size. Punching a hole to EOF needs
to be treated in teh same way as all other hole punching cases so that the
file size is never seen to change.

SGI-PV: 962012
SGI-Modid: xfs-linux-melb:xfs-kern:28641a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Vlad Apostolov <vapo@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>

1 files changed, 18 insertions, 10 deletions

diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 70bc82f65311..6420ca8df5ec 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -1201,13 +1201,15 @@ xfs_fsync(
 }
 
 /*
- * This is called by xfs_inactive to free any blocks beyond eof,
- * when the link count isn't zero.
+ * This is called by xfs_inactive to free any blocks beyond eof
+ * when the link count isn't zero and by xfs_dm_punch_hole() when
+ * punching a hole to EOF.
  */
-STATIC int
-xfs_inactive_free_eofblocks(
+int
+xfs_free_eofblocks(
         xfs_mount_t     *mp,
-        xfs_inode_t     *ip)
+        xfs_inode_t     *ip,
+        int             flags)
 {
         xfs_trans_t     *tp;
         int             error;
@@ -1216,6 +1218,7 @@ xfs_inactive_free_eofblocks(
         xfs_filblks_t   map_len;
         int             nimaps;
         xfs_bmbt_irec_t imap;
+        int             use_iolock = (flags & XFS_FREE_EOF_LOCK);
 
         /*
          * Figure out if there are any blocks beyond the end
@@ -1256,11 +1259,13 @@ xfs_inactive_free_eofblocks(
                  * cache and we can't
                  * do that within a transaction.
                  */
-                xfs_ilock(ip, XFS_IOLOCK_EXCL);
+                if (use_iolock)
+                        xfs_ilock(ip, XFS_IOLOCK_EXCL);
                 error = xfs_itruncate_start(ip, XFS_ITRUNC_DEFINITE,
                                     ip->i_size);
                 if (error) {
-                        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
+                        if (use_iolock)
+                                xfs_iunlock(ip, XFS_IOLOCK_EXCL);
                         return error;
                 }
 
@@ -1297,7 +1302,8 @@ xfs_inactive_free_eofblocks(
                         error = xfs_trans_commit(tp,
                                                 XFS_TRANS_RELEASE_LOG_RES);
                 }
-                xfs_iunlock(ip, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL);
+                xfs_iunlock(ip, (use_iolock ? (XFS_IOLOCK_EXCL|XFS_ILOCK_EXCL)
+                                            : XFS_ILOCK_EXCL));
         }
         return error;
 }
@@ -1573,7 +1579,8 @@ xfs_release(
                      (ip->i_df.if_flags & XFS_IFEXTENTS))  &&
                     (!(ip->i_d.di_flags &
                                 (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)))) {
-                        if ((error = xfs_inactive_free_eofblocks(mp, ip)))
+                        error = xfs_free_eofblocks(mp, ip, XFS_FREE_EOF_LOCK);
+                        if (error)
                                 return error;
                         /* Update linux inode block count after free above */
                         vn_to_inode(vp)->i_blocks = XFS_FSB_TO_BB(mp,
@@ -1654,7 +1661,8 @@ xfs_inactive(
                      (!(ip->i_d.di_flags &
                                 (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)) ||
                       (ip->i_delayed_blks != 0)))) {
-                        if ((error = xfs_inactive_free_eofblocks(mp, ip)))
+                        error = xfs_free_eofblocks(mp, ip, XFS_FREE_EOF_LOCK);
+                        if (error)
                                 return VN_INACTIVE_CACHE;
                         /* Update linux inode block count after free above */
                         vn_to_inode(vp)->i_blocks = XFS_FSB_TO_BB(mp,