Leverage fact that dm_queue_split() enables use of noclone support even
for targets that require additional splitting (via ti->max_io_len).
To achieve this move noclone processing from dm_make_request() to
dm_process_bio() and check if bio->bi_end_io is already set to
noclone_endio. This also fixes dm_wq_work() to be able to support
noclone bios (because it calls dm_process_bio()).
While at it, clean up ->map() return processing to be comparable to
__map_bio() and add some code comments that explain why certain
conditionals exist to prevent the use of noclone.
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm.c | 102 +++++++++++++++++++++++++++++++++-----------------------
1 file changed, 61 insertions(+), 41 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index cbda11b34635..6868b80fc70c 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1769,14 +1769,74 @@ static blk_qc_t dm_process_bio(struct mapped_device *md,
* If in ->make_request_fn we need to use blk_queue_split(), otherwise
* queue_limits for abnormal requests (e.g. discard, writesame, etc)
* won't be imposed.
+ *
+ * For normal READ and WRITE requests we benefit from upfront splitting
+ * via dm_queue_split() because we can then leverage noclone support below.
*/
- if (current->bio_list) {
+ if (current->bio_list && (bio->bi_end_io != noclone_endio)) {
+ /*
+ * It is fine to use {blk,dm}_queue_split() before opting to use noclone
+ * because any ->bi_private and ->bi_end_io will get saved off below.
+ * Once noclone_endio() is called the bio_chain's endio will kick in.
+ * - __split_and_process_bio() can split further, but any targets that
+ * require late _DM_ initiated splitting (e.g. dm_accept_partial_bio()
+ * callers) shouldn't set ti->no_clone.
+ */
if (is_abnormal_io(bio))
blk_queue_split(md->queue, &bio);
else
dm_queue_split(md, ti, &bio);
}
+ if (dm_table_supports_noclone(map) &&
+ (bio_op(bio) == REQ_OP_READ || bio_op(bio) == REQ_OP_WRITE) &&
+ likely(!(bio->bi_opf & REQ_PREFLUSH)) &&
+ likely(!bio_integrity(bio)) && /* integrity requires specialized processing */
+ likely(!dm_stats_used(&md->stats))) { /* noclone doesn't support dm-stats */
+ int r;
+ struct dm_noclone *noclone;
+
+ /* Already been here if bio->bi_end_io is noclone_endio, reentered via dm_wq_work() */
+ if (bio->bi_end_io != noclone_endio) {
+ noclone = kmem_cache_alloc(_noclone_cache, GFP_NOWAIT);
+ if (unlikely(!noclone))
+ goto no_fast_path;
+
+ noclone->md = md;
+ noclone->start_time = jiffies;
+ noclone->orig_bi_end_io = bio->bi_end_io;
+ noclone->orig_bi_private = bio->bi_private;
+ bio->bi_end_io = noclone_endio;
+ bio->bi_private = noclone;
+ }
+
+ start_io_acct(md, bio);
+ r = ti->type->map(ti, bio);
+ switch (r) {
+ case DM_MAPIO_SUBMITTED:
+ break;
+ case DM_MAPIO_REMAPPED:
+ /* the bio has been remapped so dispatch it */
+ if (md->type == DM_TYPE_NVME_BIO_BASED)
+ ret = direct_make_request(bio);
+ else
+ ret = generic_make_request(bio);
+ break;
+ case DM_MAPIO_KILL:
+ bio_io_error(bio);
+ break;
+ case DM_MAPIO_REQUEUE:
+ bio->bi_status = BLK_STS_DM_REQUEUE;
+ noclone_endio(bio);
+ break;
+ default:
+ DMWARN("unimplemented target map return value: %d", r);
+ BUG();
+ }
+
+ return ret;
+ }
+no_fast_path:
if (dm_get_md_type(md) == DM_TYPE_NVME_BIO_BASED)
return __process_bio(md, map, bio, ti);
else
@@ -1803,48 +1863,8 @@ static blk_qc_t dm_make_request(struct request_queue *q, struct bio *bio)
return ret;
}
- if (dm_table_supports_noclone(map) &&
- (bio_op(bio) == REQ_OP_READ || bio_op(bio) == REQ_OP_WRITE) &&
- likely(!(bio->bi_opf & REQ_PREFLUSH)) &&
- !bio_flagged(bio, BIO_CHAIN) &&
- likely(!bio_integrity(bio)) &&
- likely(!dm_stats_used(&md->stats))) {
- int r;
- struct dm_noclone *noclone;
- struct dm_target *ti = dm_table_find_target(map, bio->bi_iter.bi_sector);
- if (unlikely(!dm_target_is_valid(ti)))
- goto no_fast_path;
- if (unlikely(bio_sectors(bio) > max_io_len(bio->bi_iter.bi_sector, ti)))
- goto no_fast_path;
- noclone = kmem_cache_alloc(_noclone_cache, GFP_NOWAIT);
- if (unlikely(!noclone))
- goto no_fast_path;
- noclone->md = md;
- noclone->start_time = jiffies;
- noclone->orig_bi_end_io = bio->bi_end_io;
- noclone->orig_bi_private = bio->bi_private;
- bio->bi_end_io = noclone_endio;
- bio->bi_private = noclone;
- start_io_acct(md, bio);
- r = ti->type->map(ti, bio);
- ret = BLK_QC_T_NONE;
- if (likely(r == DM_MAPIO_REMAPPED)) {
- ret = generic_make_request(bio);
- } else if (likely(r == DM_MAPIO_SUBMITTED)) {
- } else if (r == DM_MAPIO_KILL) {
- bio->bi_status = BLK_STS_IOERR;
- noclone_endio(bio);
- } else {
- DMWARN("unimplemented target map return value: %d", r);
- BUG();
- }
- goto put_table_ret;
- }
-
-no_fast_path:
ret = dm_process_bio(md, map, bio);
-put_table_ret:
dm_put_live_table(md, srcu_idx);
return ret;
}
--
2.15.0
--
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