Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756811AbaJHWF6 (ORCPT ); Wed, 8 Oct 2014 18:05:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:23831 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754357AbaJHWF5 (ORCPT ); Wed, 8 Oct 2014 18:05:57 -0400 From: Mike Snitzer To: axboe@kernel.dk, linux-kernel@vger.kernel.org Cc: martin.petersen@oracle.com, dm-devel@redhat.com Subject: [PATCH] block: fix alignment_offset math that assumes io_min is a power-of-2 Date: Wed, 8 Oct 2014 18:05:52 -0400 Message-Id: <1412805952-15316-1-git-send-email-snitzer@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The math in both blk_stack_limits() and queue_limit_alignment_offset() assume that a block device's io_min (aka minimum_io_size) is always a power-of-2. Fix the math such that it works for non-power-of-2 io_min. This issue (of alignment_offset != 0) became apparent when testing dm-thinp with a thinp blocksize that matches a RAID6 stripesize of 1280K. Commit fdfb4c8c1 ("dm thin: set minimum_io_size to pool's data block size") unlocked the potential for alignment_offset != 0 due to the dm-thin-pool's io_min possibly being a non-power-of-2. Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- block/blk-settings.c | 4 ++-- include/linux/blkdev.h | 5 ++--- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/block/blk-settings.c b/block/blk-settings.c index f1a1795..aa02247 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -574,7 +574,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, bottom = max(b->physical_block_size, b->io_min) + alignment; /* Verify that top and bottom intervals line up */ - if (max(top, bottom) & (min(top, bottom) - 1)) { + if (max(top, bottom) % min(top, bottom)) { t->misaligned = 1; ret = -1; } @@ -619,7 +619,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, /* Find lowest common alignment_offset */ t->alignment_offset = lcm(t->alignment_offset, alignment) - & (max(t->physical_block_size, t->io_min) - 1); + % max(t->physical_block_size, t->io_min); /* Verify that new alignment_offset is on a logical block boundary */ if (t->alignment_offset & (t->logical_block_size - 1)) { diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 038b40f..e077b92 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1279,10 +1279,9 @@ static inline int queue_alignment_offset(struct request_queue *q) static inline int queue_limit_alignment_offset(struct queue_limits *lim, sector_t sector) { unsigned int granularity = max(lim->physical_block_size, lim->io_min); - unsigned int alignment = (sector << 9) & (granularity - 1); + unsigned int alignment = sector_div(sector, granularity >> 9); - return (granularity + lim->alignment_offset - alignment) - & (granularity - 1); + return (granularity + lim->alignment_offset - alignment) % granularity; } static inline int bdev_alignment_offset(struct block_device *bdev) -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/