From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751643AbcFCD1z (ORCPT ); Thu, 2 Jun 2016 23:27:55 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:17436 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751238AbcFCD0f (ORCPT ); Thu, 2 Jun 2016 23:26:35 -0400 To: Shaohua Li Cc: , , , , , , Subject: Re: [PATCH] block: correctly fallback for zeroout From: "Martin K. Petersen" Organization: Oracle Corporation References: <20160526180813.GA49039@shli-mbp.local> Date: Thu, 02 Jun 2016 23:26:22 -0400 In-Reply-To: <20160526180813.GA49039@shli-mbp.local> (Shaohua Li's message of "Thu, 26 May 2016 11:08:14 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> "Shaohua" == Shaohua Li writes: Shaohua> blkdev_issue_zeroout try discard/writesame first, if they fail, Shaohua> zeroout fallback to regular write. The problem is Shaohua> discard/writesame doesn't return error for -EOPNOTSUPP, then Shaohua> zeroout can't do fallback and leave disk data not Shaohua> changed. zeroout should have guaranteed zero-fill behavior. As discussed at LSF/MM, let's explicitly separate the exported/ioctl() functions from the __/do_foo_bar iterators. That's essentially what you have done. And then put all error handling and policy in the ioctl() wrappers instead of the worker functions. diff --git a/block/blk-lib.c b/block/blk-lib.c index 23d7f30..232f9ea 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -95,8 +95,9 @@ EXPORT_SYMBOL(__blkdev_issue_discard); * Description: * Issue a discard request for the sectors in question. */ -int blkdev_issue_discard(struct block_device *bdev, sector_t sector, - sector_t nr_sects, gfp_t gfp_mask, unsigned long flags) +static int do_blkdev_issue_discard(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask, unsigned long flags, + bool ignore_nosupport) { int type = REQ_WRITE | REQ_DISCARD; struct bio *bio = NULL; @@ -111,13 +112,20 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, &bio); if (!ret && bio) { ret = submit_bio_wait(type, bio); - if (ret == -EOPNOTSUPP) + if (ignore_nosupport && ret == -EOPNOTSUPP) ret = 0; } blk_finish_plug(&plug); return ret; } + +int blkdev_issue_discard(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask, unsigned long flags) +{ + return do_blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, + flags, true); +} I'd prefer to do the EOPNOTSUPP mapping for the ioctl here instead of in the do_blkdev_issue_discard() function. Then you don't need the ignore_nosupport flag. EXPORT_SYMBOL(blkdev_issue_discard); /** @@ -131,9 +139,9 @@ EXPORT_SYMBOL(blkdev_issue_discard); * Description: * Issue a write same request for the sectors in question. */ -int blkdev_issue_write_same(struct block_device *bdev, sector_t sector, +static int do_blkdev_issue_write_same(struct block_device *bdev, sector_t sector, sector_t nr_sects, gfp_t gfp_mask, - struct page *page) + struct page *page, bool ignore_nosupport) { struct request_queue *q = bdev_get_queue(bdev); unsigned int max_write_same_sectors; @@ -167,7 +175,15 @@ int blkdev_issue_write_same(struct block_device *bdev, sector_t sector, if (bio) ret = submit_bio_wait(REQ_WRITE | REQ_WRITE_SAME, bio); - return ret != -EOPNOTSUPP ? ret : 0; + return (ret != -EOPNOTSUPP || !ignore_nosupport) ? ret : 0; +} + +int blkdev_issue_write_same(struct block_device *bdev, sector_t sector, + sector_t nr_sects, gfp_t gfp_mask, + struct page *page) +{ + return do_blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, + page, true); } EXPORT_SYMBOL(blkdev_issue_write_same); There should not be a "soft" fail for WRITE SAME, it's not a hint. @@ -238,12 +254,13 @@ int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, struct request_queue *q = bdev_get_queue(bdev); if (discard && blk_queue_discard(q) && q->limits.discard_zeroes_data && - blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, 0) == 0) + do_blkdev_issue_discard(bdev, sector, nr_sects, gfp_mask, 0, + false) == 0) return 0; if (bdev_write_same(bdev) && - blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, - ZERO_PAGE(0)) == 0) + do_blkdev_issue_write_same(bdev, sector, nr_sects, gfp_mask, + ZERO_PAGE(0), false) == 0) return 0; return __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask); -- Martin K. Petersen Oracle Linux Engineering