On Tue, Mar 29, 2016 at 02:18:33PM -0700, Christoph Hellwig wrote: > On Tue, Mar 29, 2016 at 09:42:33AM -0700, Shaohua Li wrote: > > bio_alloc_bioset() allocates bvecs from bvec_slabs which can only > > allocate maximum 256 bvec (eg, 1M for 4k pages). We can't bump > > BLK_DEF_MAX_SECTORS to exceed this value otherwise bio_alloc_bioset will > > fail. > > This might be true, but it's not a good enough reason. Request based > driver couldn't care less about the limits of bio_alloc_bioset. > > It seems the bug is that somone (would be great to know whoe exactly) > passes a too large value to bio_alloc_bioset. And given that we still > have bio_add_page around for actually adding pages to a bio it seems > like the proper fix would be to simply clamp down the actual allocation > and segment limit inside bio_alloc_bioset. Which would also help to > eventually remove code doing just that in tons of callers. The problem is bcache allocates a big bio (with bio_alloc). The bio is split with blk_queue_split, but it isn't split to small size because queue limit. the bio is cloned later in md, which uses bio_alloc_bioset. bio_alloc_bioset itself can't allocate big size bio. -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html