btrfs: zoned: wait for data BG to be finished on direct IO allocation

Running the fio command below on a ZNS device results in "Resource
temporarily unavailable" error.

  $ sudo fio --name=w --directory=/mnt --filesize=1GB --bs=16MB --numjobs=16 \
        --rw=write --ioengine=libaio --iodepth=128 --direct=1

  fio: io_u error on file /mnt/w.2.0: Resource temporarily unavailable: write offset=117440512, buflen=16777216
  fio: io_u error on file /mnt/w.2.0: Resource temporarily unavailable: write offset=134217728, buflen=16777216
  ...

This happens because -EAGAIN error returned from btrfs_reserve_extent()
called from btrfs_new_extent_direct() is spilling over to the userland.

btrfs_reserve_extent() returns -EAGAIN when there is no active zone
available. Then, the caller should wait for some other on-going IO to
finish a zone and retry the allocation.

This logic is already implemented for buffered write in cow_file_range(),
but it is missing for the direct IO counterpart. Implement the same logic
for it.
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: 2ce543f4 ("btrfs: zoned: wait until zone is finished when allocation didn't progress")
CC: stable@vger.kernel.org # 6.1+
Tested-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -6979,8 +6979,15 @@ static struct extent_map *btrfs_new_extent_direct(struct btrfs_inode *inode,
 	int ret;
 
 	alloc_hint = get_extent_allocation_hint(inode, start, len);
+again:
 	ret = btrfs_reserve_extent(root, len, len, fs_info->sectorsize,
 				   0, alloc_hint, &ins, 1, 1);
+	if (ret == -EAGAIN) {
+		ASSERT(btrfs_is_zoned(fs_info));
+		wait_on_bit_io(&inode->root->fs_info->flags, BTRFS_FS_NEED_ZONE_FINISH,
+			       TASK_UNINTERRUPTIBLE);
+		goto again;
+	}
 	if (ret)
 		return ERR_PTR(ret);