btrfs: get rid of btrfs_read_dev_super()

The function is introduced by commit a512bbf855ff ("Btrfs: superblock
duplication") at the beginning of btrfs.

It leaved a comment saying we'd need a special mount option to read all
super blocks, but it's never been implemented and there was not
need/request for it. The check/rescue tools are able to start from a
specific copy and use it as primary eventually.

This means btrfs_read_dev_super() is always reading the first super
block, making all the code finding the latest super block unnecessary.

Just remove that function and replace all call sites with
btrfs_read_disk_super(bdev, 0, false).

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

3 files changed, 2 insertions, 31 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1768618d8a60..308e8f384ecb 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3317,7 +3317,7 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
 	/*
 	 * Read super block and check the signature bytes only
 	 */
-	disk_super = btrfs_read_dev_super(fs_devices->latest_dev->bdev);
+	disk_super = btrfs_read_disk_super(fs_devices->latest_dev->bdev, 0, false);
 	if (IS_ERR(disk_super)) {
 		ret = PTR_ERR(disk_super);
 		goto fail_alloc;
@@ -3712,34 +3712,6 @@ static void btrfs_end_super_write(struct bio *bio)
 	bio_put(bio);
 }
 
-struct btrfs_super_block *btrfs_read_dev_super(struct block_device *bdev)
-{
-	struct btrfs_super_block *super, *latest = NULL;
-	int i;
-	u64 transid = 0;
-
-	/* we would like to check all the supers, but that would make
-	 * a btrfs mount succeed after a mkfs from a different FS.
-	 * So, we need to add a special mount option to scan for
-	 * later supers, using BTRFS_SUPER_MIRROR_MAX instead
-	 */
-	for (i = 0; i < 1; i++) {
-		super = btrfs_read_disk_super(bdev, i, false);
-		if (IS_ERR(super))
-			continue;
-
-		if (!latest || btrfs_super_generation(super) > transid) {
-			if (latest)
-				btrfs_release_disk_super(super);
-
-			latest = super;
-			transid = btrfs_super_generation(super);
-		}
-	}
-
-	return super;
-}
-
 /*
  * Write superblock @sb to the @device. Do not wait for completion, all the
  * folios we use for writing are locked.
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 0ac9baf1215f..864a55a96226 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -58,7 +58,6 @@ int btrfs_validate_super(const struct btrfs_fs_info *fs_info,
 			 const struct btrfs_super_block *sb, int mirror_num);
 int btrfs_check_features(struct btrfs_fs_info *fs_info, bool is_rw_mount);
 int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors);
-struct btrfs_super_block *btrfs_read_dev_super(struct block_device *bdev);
 int btrfs_commit_super(struct btrfs_fs_info *fs_info);
 struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
 					const struct btrfs_key *key);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 8478fb5ce446..db1c924a636b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -493,7 +493,7 @@ btrfs_get_bdev_and_sb(const char *device_path, blk_mode_t flags, void *holder,
 		}
 	}
 	invalidate_bdev(bdev);
-	*disk_super = btrfs_read_dev_super(bdev);
+	*disk_super = btrfs_read_disk_super(bdev, 0, false);
 	if (IS_ERR(*disk_super)) {
 		ret = PTR_ERR(*disk_super);
 		fput(*bdev_file);