Messages in this thread | | | Date | Tue, 29 Mar 2016 14:18:33 -0700 | From | Christoph Hellwig <> | Subject | Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big |
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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.
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