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btrfs_get_bdev_and_sb(): call set_blocksize() only for exclusive opens

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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@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2024-04-18 00:21:25 -04:00
parent b1439b179d
commit b85c42981a
1 changed files with 7 additions and 4 deletions
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11
fs/btrfs/volumes.c
View file

@ -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;
}