2 files changed, 29 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 9f2e398a5616..e9c21454b9e2 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -1318,6 +1318,8 @@ xfs_fs_remount(
 
         /* ro -> rw */
         if ((mp->m_flags & XFS_MOUNT_RDONLY) && !(*flags & MS_RDONLY)) {
+                __uint64_t resblks;
+
                 mp->m_flags &= ~XFS_MOUNT_RDONLY;
                 if (mp->m_flags & XFS_MOUNT_BARRIER)
                         xfs_mountfs_check_barriers(mp);
@@ -1335,11 +1337,37 @@ xfs_fs_remount(
                         }
                         mp->m_update_flags = 0;
                 }
+
+                /*
+                 * Fill out the reserve pool if it is empty. Use the stashed
+                 * value if it is non-zero, otherwise go with the default.
+                 */
+                if (mp->m_resblks_save) {
+                        resblks = mp->m_resblks_save;
+                        mp->m_resblks_save = 0;
+                } else {
+                        resblks = mp->m_sb.sb_dblocks;
+                        do_div(resblks, 20);
+                        resblks = min_t(__uint64_t, resblks, 1024);
+                }
+                xfs_reserve_blocks(mp, &resblks, NULL);
         }
 
         /* rw -> ro */
         if (!(mp->m_flags & XFS_MOUNT_RDONLY) && (*flags & MS_RDONLY)) {
+                /*
+                 * After we have synced the data but before we sync the
+                 * metadata, we need to free up the reserve block pool so that
+                 * the used block count in the superblock on disk is correct at
+                 * the end of the remount. Stash the current reserve pool size
+                 * so that if we get remounted rw, we can return it to the same
+                 * size.
+                 */
+                __uint64_t resblks = 0;
+
                 xfs_quiesce_data(mp);
+                mp->m_resblks_save = mp->m_resblks;
+                xfs_reserve_blocks(mp, &resblks, NULL);
                 xfs_quiesce_attr(mp);
                 mp->m_flags |= XFS_MOUNT_RDONLY;
         }
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index f4d1441f3f15..02d45f213e58 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -225,6 +225,7 @@ typedef struct xfs_mount {
         __uint64_t              m_maxioffset;   /* maximum inode offset */
         __uint64_t              m_resblks;      /* total reserved blocks */
         __uint64_t              m_resblks_avail;/* available reserved blocks */
+        __uint64_t              m_resblks_save; /* reserved blks @ remount,ro */
         int                     m_dalign;       /* stripe unit */
         int                     m_swidth;       /* stripe width */
         int                     m_sinoalign;    /* stripe unit inode alignment */