On Tue, Apr 05, 2016 at 05:49:02AM -0700, Christoph Hellwig wrote:

On Tue, Apr 05, 2016 at 07:56:56PM +0800, Ming Lei wrote:

quoted

diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c
index 86a0bb8..1c48462 100644
--- a/drivers/md/bcache/io.c
+++ b/drivers/md/bcache/io.c

@@ -26,8 +26,7 @@ struct bio *bch_bbio_alloc(struct cache_set *c)
 
 	bio_init(bio);
 	bio->bi_flags		|= BIO_POOL_NONE << BIO_POOL_OFFSET;
-	bio->bi_max_vecs	 = bucket_pages(c);
-	bio->bi_io_vec		 = bio->bi_inline_vecs;
+	bio_set_vec_table(bio, bio->bi_inline_vecs, bucket_pages(c));

All this bcache code needs to move away from bio_init on a bio
embedded in a driver private structure toward properly using
bio_alloc / bio_alloc_bioset.  That will also fix the crash
with bcache over md that Shaohua reported, so I'd suggest to fast
track this part of the series.

Why?

bio_init() is a publicly exported function, it's always been one and bcache is
ot the only driver to use it directly.

bios with > BIO_MAX_PAGES bvecs is a separate issue; I would argue that the bug
is in md's queue_limits; it uses blk_set_stacking_limits() which sets
max_segments = USHRT_MAX, which is wrong if it's going to clone the biovec.