Re: [REGRESSION] "split bio_kmalloc from bio_alloc_bioset" causing crash shortly after bootup

[Christoph Hellwig <hch@lst.de>]

On Tue, Feb 23, 2021 at 03:51:23AM +0000, Chaitanya Kulkarni wrote:
> Looking at the other call sites do we need something like following ?

> Since __blk_queue_bounce() passes the NULL for the passthru case as a
> bio_set value ?

Well, that is a somewhat odd calling convention.  What about the patch below
instead?  That being we really need to kill this bouncing code off..


diff --git a/block/bounce.c b/block/bounce.c
index fc55314aa4269a..789fbcacb1e92a 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -214,9 +214,9 @@ static void bounce_end_io_read_isa(struct bio *bio)
 	__bounce_end_io_read(bio, &isa_page_pool);
 }
 
-static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
-		struct bio_set *bs)
+static struct bio *bounce_clone_bio(struct bio *bio_src, bool passthrough)
 {
+	unsigned int nr_vecs = bio_segments(bio_src);
 	struct bvec_iter iter;
 	struct bio_vec bv;
 	struct bio *bio;
@@ -242,8 +242,10 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
 	 *    asking for trouble and would force extra work on
 	 *    __bio_clone_fast() anyways.
 	 */
-
-	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
+	if (passthrough)
+		bio = bio_kmalloc(GFP_NOIO, nr_vecs);
+	else
+		bio = bio_alloc_bioset(GFP_NOIO, nr_vecs, &bounce_bio_set);
 	if (!bio)
 		return NULL;
 	bio->bi_bdev		= bio_src->bi_bdev;
@@ -269,11 +271,11 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
 		break;
 	}
 
-	if (bio_crypt_clone(bio, bio_src, gfp_mask) < 0)
+	if (bio_crypt_clone(bio, bio_src, GFP_NOIO) < 0)
 		goto err_put;
 
 	if (bio_integrity(bio_src) &&
-	    bio_integrity_clone(bio, bio_src, gfp_mask) < 0)
+	    bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0)
 		goto err_put;
 
 	bio_clone_blkg_association(bio, bio_src);
@@ -313,8 +315,7 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 		submit_bio_noacct(*bio_orig);
 		*bio_orig = bio;
 	}
-	bio = bounce_clone_bio(*bio_orig, GFP_NOIO, passthrough ? NULL :
-			&bounce_bio_set);
+	bio = bounce_clone_bio(*bio_orig, passthrough);
 
 	/*
 	 * Bvec table can't be updated by bio_for_each_segment_all(),