btrfs_get_bdev_and_sb() has two callers - btrfs_open_one_device(),
which asks for open to be exclusive and btrfs_get_dev_args_from_path(),
which doesn't. Currently it does set_blocksize() in all cases.
I'm rather dubious about the need to do set_blocksize() anywhere in btrfs,
to be honest - there's some access to page cache of underlying block
devices in there, but it's nowhere near the hot paths, AFAICT.
In any case, btrfs_get_dev_args_from_path() only needs to read
the on-disk superblock and copy several fields out of it; all
callers are only interested in devices that are already opened
and brought into per-filesystem set, so setting the block size
is redundant for those and actively harmful if we are given
a pathname of unrelated device.
So we only need btrfs_get_bdev_and_sb() to call set_blocksize()
when it's asked to open exclusive.
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/btrfs/volumes.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f15591f3e54f..43af5a9fb547 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -482,10 +482,12 @@ btrfs_get_bdev_and_sb(const char *device_path, blk_mode_t flags, void *holder,
if (flush)
sync_blockdev(bdev);
- ret = set_blocksize(bdev, BTRFS_BDEV_BLOCKSIZE);
- if (ret) {
- fput(*bdev_file);
- goto error;
+ if (holder) {
+ ret = set_blocksize(bdev, BTRFS_BDEV_BLOCKSIZE);
+ if (ret) {
+ fput(*bdev_file);
+ goto error;
+ }
}
invalidate_bdev(bdev);
*disk_super = btrfs_read_dev_super(bdev);
@@ -498,6 +500,7 @@ btrfs_get_bdev_and_sb(const char *device_path, blk_mode_t flags, void *holder,
return 0;
error:
+ *disk_super = NULL;
*bdev_file = NULL;
return ret;
}
--
2.39.2
