Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759264AbcDEPYe (ORCPT ); Tue, 5 Apr 2016 11:24:34 -0400 Received: from mail-yw0-f195.google.com ([209.85.161.195]:35945 "EHLO mail-yw0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759216AbcDEPYb (ORCPT ); Tue, 5 Apr 2016 11:24:31 -0400 MIME-Version: 1.0 In-Reply-To: <20160405124902.GA11986@infradead.org> References: <1459857443-20611-1-git-send-email-tom.leiming@gmail.com> <1459857443-20611-12-git-send-email-tom.leiming@gmail.com> <20160405124902.GA11986@infradead.org> Date: Tue, 5 Apr 2016 23:24:30 +0800 Message-ID: Subject: Re: [PATCH 11/27] bcache: io.c: use bio_set_vec_table From: Ming Lei To: Christoph Hellwig Cc: Jens Axboe , Linux Kernel Mailing List , linux-block@vger.kernel.org, Boaz Harrosh , Kent Overstreet , Shaohua Li , "open list:BCACHE (BLOCK LAYER CACHE)" , "open list:SOFTWARE RAID (Multiple Disks) SUPPORT" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1553 Lines: 35 On Tue, Apr 5, 2016 at 8:49 PM, Christoph Hellwig wrote: > On Tue, Apr 05, 2016 at 07:56:56PM +0800, Ming Lei wrote: >> 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. I suggest to keep this usage for the following reasons: - bio can be embedded into one biger instance, which is often allocated dynamically, so one extra allocation for bio can be avoided. - we should support arbitrary bio size by this way, at least bio_add_page() supports this usage. Also code gets lots of simplication with arbitrary bio size support, such as prio_io(): bcache BTW, the root cause for bcache crash still isn't clear now because blk_bio_segment_split() should split big bio into proper size with all queue's limits. Maybe the max segment limit isn't figured out correctly. Thanks, Ming Lei