btrfs: lift read-write mount setup from mount and remount

Mounting rw and remounting from ro to rw naturally share invariants and
functionality which result in a correctly setup rw filesystem. Luckily,
there is even a strong unity in the code which implements them. In
mount's open_ctree, these operations mostly happen after an early return
for ro file systems, and in remount, they happen in a section devoted to
remounting ro->rw, after some remount specific validation passes.

However, there are unfortunately a few differences. There are small
deviations in the order of some of the operations, remount does not
start orphan cleanup in root_tree or fs_tree, remount does not create
the free space tree, and remount does not handle "one-shot" mount
options like clear_cache and uuid tree rescan.

Since we want to add building the free space tree to remount, and also
to start the same orphan cleanup process on a filesystem mounted as ro
then remounted rw, we would benefit from unifying the logic between the
two code paths.

This patch only lifts the existing common functionality, and leaves a
natural path for fixing the discrepancies.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 6 insertions, 31 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 455d924b8d62..49b4a16488c9 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1885,7 +1885,6 @@ static inline void btrfs_remount_cleanup(struct btrfs_fs_info *fs_info,
 static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
-	struct btrfs_root *root = fs_info->tree_root;
 	unsigned old_flags = sb->s_flags;
 	unsigned long old_opts = fs_info->mount_opt;
 	unsigned long old_compress_type = fs_info->compress_type;
@@ -1978,39 +1977,15 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 			goto restore;
 		}
 
-		ret = btrfs_cleanup_fs_roots(fs_info);
-		if (ret)
-			goto restore;
-
-		/* recover relocation */
-		mutex_lock(&fs_info->cleaner_mutex);
-		ret = btrfs_recover_relocation(root);
-		mutex_unlock(&fs_info->cleaner_mutex);
-		if (ret)
-			goto restore;
-
-		ret = btrfs_resume_balance_async(fs_info);
+		/*
+		 * NOTE: when remounting with a change that does writes, don't
+		 * put it anywhere above this point, as we are not sure to be
+		 * safe to write until we pass the above checks.
+		 */
+		ret = btrfs_start_pre_rw_mount(fs_info);
 		if (ret)
 			goto restore;
 
-		ret = btrfs_resume_dev_replace_async(fs_info);
-		if (ret) {
-			btrfs_warn(fs_info, "failed to resume dev_replace");
-			goto restore;
-		}
-
-		btrfs_qgroup_rescan_resume(fs_info);
-
-		if (!fs_info->uuid_root) {
-			btrfs_info(fs_info, "creating UUID tree");
-			ret = btrfs_create_uuid_tree(fs_info);
-			if (ret) {
-				btrfs_warn(fs_info,
-					   "failed to create the UUID tree %d",
-					   ret);
-				goto restore;
-			}
-		}
 		sb->s_flags &= ~SB_RDONLY;
 
 		set_bit(BTRFS_FS_OPEN, &fs_info->flags);