From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: [PATCH 1/2] block: simple improvements for bio->flags Date: Fri, 07 Apr 2017 11:10:44 +1000 Message-ID: <149152744444.17489.7959643077115840287.stgit@noble> References: <149152735878.17489.16036848644242802943.stgit@noble> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <149152735878.17489.16036848644242802943.stgit@noble> Sender: linux-block-owner@vger.kernel.org To: Jens Axboe Cc: linux-raid@vger.kernel.org, Mike Snitzer , Christoph Hellwig , Ming Lei , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, dm-devel@redhat.com, Shaohua Li , Alasdair Kergon List-Id: linux-raid.ids The comment for the 'flags' field of 'bio' mentions "command" which is no longer stored there, and doesn't mention the bvec pool number, which is. BIO_RESET_BITS is set in such a way that it would need to be updated if new bits were added, which is easy to miss. BVEC_POOL_BITS is larger than needed. The BVEC_POOL_IDX() ranges from 0 to 6, so 3 bits are sufficient. This patch make improvements in each of these areas. Signed-off-by: NeilBrown --- include/linux/blk_types.h | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index d703acb55d0f..ff07d891f38f 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -29,7 +29,7 @@ struct bio { * top bits REQ_OP. Use * accessors. */ - unsigned short bi_flags; /* status, command, etc */ + unsigned short bi_flags; /* status, etc and bvec pool number */ unsigned short bi_ioprio; struct bvec_iter bi_iter; @@ -102,12 +102,7 @@ struct bio { #define BIO_REFFED 8 /* bio has elevated ->bi_cnt */ #define BIO_THROTTLED 9 /* This bio has already been subjected to * throttling rules. Don't do it again. */ - -/* - * Flags starting here get preserved by bio_reset() - this includes - * BVEC_POOL_IDX() - */ -#define BIO_RESET_BITS 10 +/* See BVEC_POOL_OFFSET below before adding new flags */ /* * We support 6 different bvec pools, the last one is magic in that it @@ -117,13 +112,22 @@ struct bio { #define BVEC_POOL_MAX (BVEC_POOL_NR - 1) /* - * Top 4 bits of bio flags indicate the pool the bvecs came from. We add + * Top 3 bits of bio flags indicate the pool the bvecs came from. We add * 1 to the actual index so that 0 indicates that there are no bvecs to be * freed. */ -#define BVEC_POOL_BITS (4) +#define BVEC_POOL_BITS (3) #define BVEC_POOL_OFFSET (16 - BVEC_POOL_BITS) #define BVEC_POOL_IDX(bio) ((bio)->bi_flags >> BVEC_POOL_OFFSET) +#if (1<< BVEC_POOL_BITS) < (BVEC_POOL_NR+1) +# error "BVEC_POOL_BITS is too small" +#endif + +/* + * Flags starting here get preserved by bio_reset() - this includes + * only BVEC_POOL_IDX() + */ +#define BIO_RESET_BITS BVEC_POOL_OFFSET /* * Operations and flags common to the bio and request structures.