[RFC PATCH v1 11/17] block: avoid scheduling from non-blocking helper allocations

[Yu Kuai]

From: Yu Kuai <yukuai at fygo.io>

blk_alloc_discard_bio() and blk_rq_map_bio_alloc() can be used with
non-blocking GFP masks.  Their bio allocation now handles bdev association in
nowait mode, so the helpers can pass the target bdev directly and avoid local
open-coded association paths.

The discard helper can also be reached from io_uring with GFP_NOWAIT.  Keep
its long-loop cond_resched() only for blocking callers.

Signed-off-by: Yu Kuai <yukuai at fygo.io>
---
 block/blk-lib.c | 3 ++-
 block/blk-map.c | 7 +------
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 688bc67cbf73..b5645f8f69b6 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -56,7 +56,8 @@ struct bio *blk_alloc_discard_bio(struct block_device *bdev,
 	 * discards (like mkfs).  Be nice and allow us to schedule out to avoid
 	 * softlocking if preempt is disabled.
 	 */
-	cond_resched();
+	if (gfpflags_allow_blocking(gfp_mask))
+		cond_resched();
 	return bio;
 }
 
diff --git a/block/blk-map.c b/block/blk-map.c
index 768549f19f97..75c7b864c15a 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -46,14 +46,9 @@ static struct bio *blk_rq_map_bio_alloc(struct request *rq,
 		unsigned int nr_vecs, gfp_t gfp_mask)
 {
 	struct block_device *bdev = rq->q->disk ? rq->q->disk->part0 : NULL;
-	struct bio *bio;
 
-	bio = bio_alloc_bioset(bdev, nr_vecs, rq->cmd_flags, gfp_mask,
+	return bio_alloc_bioset(bdev, nr_vecs, rq->cmd_flags, gfp_mask,
 				&fs_bio_set);
-	if (!bio)
-		return NULL;
-
-	return bio;
 }
 
 /**
-- 
2.51.0