[PATCH RFC 08/11] btrfs: allow btrfs_map_bio() to split bio according to chunk stripe boundaries

Qu Wenruo
2021-11-28T05:55:33Z

With the new btrfs_bio_split() helper, we are able to split bio
according to chunk stripe boundaries at btrfs_map_bio() time.

Although currently due bio split at submit_extent_page() this ability is
not yet utilized.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/volumes.c | 53 +++++++++++++++++++++++++++++++---------------
1 file changed, 36 insertions(+), 17 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e6ed71195e18..7f7e13e4caa3 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6878,29 +6878,48 @@ static int submit_one_mapped_range(struct btrfs_fs_info *fs_info, struct bio *bi
blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
int mirror_num)
{
- u64 logical = bio->bi_iter.bi_sector << 9;
- u64 length = 0;
- u64 map_length;
+ const u64 orig_logical = bio->bi_iter.bi_sector << SECTOR_SHIFT;
+ const unsigned int orig_length = bio->bi_iter.bi_size;
+ const enum btrfs_map_op op = btrfs_op(bio);
+ u64 cur_logical = orig_logical;
int ret;
- struct btrfs_io_context *bioc = NULL;

- length = bio->bi_iter.bi_size;
- map_length = length;
+ while (cur_logical < orig_logical + orig_length) {
+ u64 map_length = orig_logical + orig_length - cur_logical;
+ struct btrfs_io_context *bioc = NULL;
+ struct bio *cur_bio;

- btrfs_bio_counter_inc_blocked(fs_info);
- ret = __btrfs_map_block(fs_info, btrfs_op(bio), logical,
- &map_length, &bioc, mirror_num, 1);
- if (ret) {
- btrfs_bio_counter_dec(fs_info);
- return errno_to_blk_status(ret);
- }
+ ret = __btrfs_map_block(fs_info, op, cur_logical, &map_length,
+ &bioc, mirror_num, 1);
+ if (ret)
+ return errno_to_blk_status(ret);

- ret = submit_one_mapped_range(fs_info, bio, bioc, map_length, mirror_num);
- if (ret < 0) {
+ if (cur_logical + map_length < orig_logical + orig_length) {
+ /*
+ * For now zoned write should never cross stripe
+ * boundary
+ */
+ ASSERT(bio_op(bio) != REQ_OP_ZONE_APPEND);
+
+ /* Need to split */
+ cur_bio = btrfs_bio_split(fs_info, bio, map_length);
+ if (IS_ERR(cur_bio)) {
+ btrfs_put_bioc(bioc);
+ ret = PTR_ERR(cur_bio);
+ return errno_to_blk_status(ret);
+ }
+ } else {
+ /* Can use the existing bio directly */
+ cur_bio = bio;
+ }
+ btrfs_bio_counter_inc_blocked(fs_info);
+ ret = submit_one_mapped_range(fs_info, cur_bio, bioc,
+ map_length, mirror_num);
btrfs_bio_counter_dec(fs_info);
- return errno_to_blk_status(ret);
+ if (ret < 0)
+ return errno_to_blk_status(ret);
+ cur_logical += map_length;
}
- btrfs_bio_counter_dec(fs_info);
return BLK_STS_OK;
}

--
2.34.0