1 files changed, 28 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 9f2e398..e9c2145 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;
 	}