btrfs: zoned: remove outdated WARN_ON in direct IO

In btrfs_submit_direct() there's a WAN_ON_ONCE() that will trigger if
we're submitting a DIO write on a zoned filesystem but are not using
REQ_OP_ZONE_APPEND to submit the IO to the block device.

This is a left over from a previous version where btrfs_dio_iomap_begin()
didn't use btrfs_use_zone_append() to check for sequential write only
zones.

It is an oversight from the development phase. In v11 (I think) I've
added 08f4555 ("btrfs: zoned: cache if block group is on a
sequential zone") and forgot to remove the WARN_ON_ONCE() for
544d24f ("btrfs: zoned: enable zone append writing for direct IO").

When developing auto relocation I got hit by the WARN as a block groups
where relocated to conventional zone and the dio code calls
btrfs_use_zone_append() introduced by 08f4555 to check if it can
use zone append (a.k.a. if it's a sequential zone) or not and sets the
appropriate flags for iomap.

I've never hit it in testing before, as I was relying on emulation to
test the conventional zones code but this one case wasn't hit, because
on emulation fs_info->max_zone_append_size is 0 and the WARN doesn't
trigger either.

Fixes: 544d24f ("btrfs: zoned: enable zone append writing for direct IO")
Signed-off-by: Johannes Thumshirn <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: morbidrsa

fs/btrfs/inode.c

@@ -8166,10 +8166,6 @@ static blk_qc_t btrfs_submit_direct(struct inode *inode, struct iomap *iomap,
 		bio->bi_end_io = btrfs_end_dio_bio;
 		btrfs_io_bio(bio)->logical = file_offset;
 
-		WARN_ON_ONCE(write && btrfs_is_zoned(fs_info) &&
-			     fs_info->max_zone_append_size &&
-			     bio_op(bio) != REQ_OP_ZONE_APPEND);
-
 		if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
 			status = extract_ordered_extent(BTRFS_I(inode), bio,
 							file_offset);