Re: [PATCH] block: Make __bio_clone_fast() copy bi_vcnt
From: Ming Lei <hidden>
Date: 2018-06-27 23:50:06
On Wed, Jun 27, 2018 at 01:12:31PM -0700, Bart Van Assche wrote:
quoted hunk ↗ jump to hunk
Although __bio_clone_fast() copies bi_io_vec, it does not copy bi_vcnt, the number of elements in bi_io_vec[] that contains data. Copy bi_vcnt such that code that needs this member behaves identically for original and for cloned requests. Signed-off-by: Bart Van Assche <redacted> Cc: Christoph Hellwig <hch@lst.de> Cc: Mike Snitzer <redacted> Cc: Ming Lei <redacted> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <redacted> --- block/bio.c | 1 + 1 file changed, 1 insertion(+)diff --git a/block/bio.c b/block/bio.c index f7e3d88bd0b6..55f8e0dedd69 100644 --- a/block/bio.c +++ b/block/bio.c@@ -605,6 +605,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src) bio->bi_opf = bio_src->bi_opf; bio->bi_write_hint = bio_src->bi_write_hint; bio->bi_iter = bio_src->bi_iter; + bio->bi_vcnt = bio_src->bi_vcnt; bio->bi_io_vec = bio_src->bi_io_vec;
No, don't do that. For a cloned bio, both .bi_vcnt and .bi_io_vec can't be used directly, and we have done huge such cleanup for supporting multipage bvec, that is the great idea of immutable bvecs invented by Kent. Thanks, Ming