3 files changed, 45 insertions, 2 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 3dcedfe4f759..ae8dcc406805 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -339,6 +339,7 @@ static inline unsigned long btrfs_chunk_item_size(int num_stripes)
  * File system states
  */
 #define BTRFS_FS_STATE_ERROR            0
+#define BTRFS_FS_STATE_REMOUNTING       1
 
 /* Super block flags */
 /* Errors detected */
@@ -1902,6 +1903,7 @@ struct btrfs_ioctl_defrag_range_args {
 
 #define btrfs_clear_opt(o, opt)         ((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)           ((o) |= BTRFS_MOUNT_##opt)
+#define btrfs_raw_test_opt(o, opt)      ((o) & BTRFS_MOUNT_##opt)
 #define btrfs_test_opt(root, opt)       ((root)->fs_info->mount_opt & \
                                          BTRFS_MOUNT_##opt)
 /*
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 9f67e623206d..6e6dd8cdad92 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -374,6 +374,11 @@ int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
 
         atomic_inc(&fs_info->defrag_running);
         while(1) {
+                /* Pause the auto defragger. */
+                if (test_bit(BTRFS_FS_STATE_REMOUNTING,
+                             &fs_info->fs_state))
+                        break;
+
                 if (!__need_auto_defrag(fs_info->tree_root))
                         break;
 
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index db1ba9a2ed64..68a29a1ea068 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1202,6 +1202,38 @@ static void btrfs_resize_thread_pool(struct btrfs_fs_info *fs_info,
                               new_pool_size);
 }
 
+static inline void btrfs_remount_prepare(struct btrfs_fs_info *fs_info,
+                                         unsigned long old_opts, int flags)
+{
+        set_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);
+
+        if (btrfs_raw_test_opt(old_opts, AUTO_DEFRAG) &&
+            (!btrfs_raw_test_opt(fs_info->mount_opt, AUTO_DEFRAG) ||
+             (flags & MS_RDONLY))) {
+                /* wait for any defraggers to finish */
+                wait_event(fs_info->transaction_wait,
+                           (atomic_read(&fs_info->defrag_running) == 0));
+                if (flags & MS_RDONLY)
+                        sync_filesystem(fs_info->sb);
+        }
+}
+
+static inline void btrfs_remount_cleanup(struct btrfs_fs_info *fs_info,
+                                         unsigned long old_opts)
+{
+        /*
+         * We need cleanup all defragable inodes if the autodefragment is
+         * close or the fs is R/O.
+         */
+        if (btrfs_raw_test_opt(old_opts, AUTO_DEFRAG) &&
+            (!btrfs_raw_test_opt(fs_info->mount_opt, AUTO_DEFRAG) ||
+             (fs_info->sb->s_flags & MS_RDONLY))) {
+                btrfs_cleanup_defrag_inodes(fs_info);
+        }
+
+        clear_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);
+}
+
 static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 {
         struct btrfs_fs_info *fs_info = btrfs_sb(sb);
@@ -1215,6 +1247,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
         unsigned int old_metadata_ratio = fs_info->metadata_ratio;
         int ret;
 
+        btrfs_remount_prepare(fs_info, old_opts, *flags);
+
         ret = btrfs_parse_options(root, data);
         if (ret) {
                 ret = -EINVAL;
@@ -1225,7 +1259,7 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
                 fs_info->thread_pool_size, old_thread_pool_size);
 
         if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
-                return 0;
+                goto out;
 
         if (*flags & MS_RDONLY) {
                 /*
@@ -1280,7 +1314,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
                 }
                 sb->s_flags &= ~MS_RDONLY;
         }
-
+out:
+        btrfs_remount_cleanup(fs_info, old_opts);
         return 0;
 
 restore:
@@ -1297,6 +1332,7 @@ restore:
         btrfs_resize_thread_pool(fs_info,
                 old_thread_pool_size, fs_info->thread_pool_size);
         fs_info->metadata_ratio = old_metadata_ratio;
+        btrfs_remount_cleanup(fs_info, old_opts);
         return ret;
 }