From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5467C433DB for ; Thu, 18 Mar 2021 20:28:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8A7C964F18 for ; Thu, 18 Mar 2021 20:28:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233068AbhCRU17 (ORCPT ); Thu, 18 Mar 2021 16:27:59 -0400 Received: from mx2.suse.de ([195.135.220.15]:43790 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233060AbhCRU14 (ORCPT ); Thu, 18 Mar 2021 16:27:56 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id C327EAC1E; Thu, 18 Mar 2021 20:27:54 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 116A3DA6E2; Thu, 18 Mar 2021 21:25:52 +0100 (CET) Date: Thu, 18 Mar 2021 21:25:51 +0100 From: David Sterba To: Qu Wenruo Cc: Omar Sandoval , linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Al Viro , Christoph Hellwig , Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v8 04/10] btrfs: fix check_data_csum() error message for direct I/O Message-ID: <20210318202551.GA7604@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Qu Wenruo , Omar Sandoval , linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, Al Viro , Christoph Hellwig , Dave Chinner , Jann Horn , Amir Goldstein , Aleksa Sarai , linux-api@vger.kernel.org, kernel-team@fb.com References: <3a20de6d6ea2a8ebbed0637480f9aa8fff8da19c.1615922644.git.osandov@fb.com> <885fa39a-713f-f594-53ae-241d9cd7a113@gmx.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Thu, Mar 18, 2021 at 07:47:29AM +0800, Qu Wenruo wrote: > > > On 2021/3/18 上午2:33, Omar Sandoval wrote: > > On Wed, Mar 17, 2021 at 07:21:46PM +0800, Qu Wenruo wrote: > >> > >> > >> On 2021/3/17 上午3:43, Omar Sandoval wrote: > >>> From: Omar Sandoval > >>> > >>> Commit 1dae796aabf6 ("btrfs: inode: sink parameter start and len to > >>> check_data_csum()") replaced the start parameter to check_data_csum() > >>> with page_offset(), but page_offset() is not meaningful for direct I/O > >>> pages. Bring back the start parameter. > >> > >> So direct IO pages doesn't have page::index set at all? > > > > No, they don't. Usually you do direct I/O into an anonymous page, but I > > suppose you could even do direct I/O into a page mmap'd from another > > file or filesystem. In either case, the index isn't meaningful for the > > file you're doing direct I/O from. > > > >> Any reproducer? I'd like to try to reproduce it first. > > > > The easiest way to see this issue is to apply this patch: > > > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > > index 2a92211439e8..a962b3026573 100644 > > --- a/fs/btrfs/inode.c > > +++ b/fs/btrfs/inode.c > > @@ -3114,6 +3114,9 @@ static int check_data_csum(struct inode *inode, struct btrfs_io_bio *io_bio, > > u8 *csum_expected; > > u8 csum[BTRFS_CSUM_SIZE]; > > > > + WARN_ONCE(page_offset(page) + pgoff != start, > > + "page offset %llu != start %llu\n", > > + page_offset(page) + pgoff, start); > > ASSERT(pgoff + len <= PAGE_SIZE); > > > > offset_sectors = bio_offset >> fs_info->sectorsize_bits; > > > > Run this simple test: > > > > $ dd if=/dev/zero of=foo bs=4k count=1024 > > 1024+0 records in > > 1024+0 records out > > 4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.00456495 s, 919 MB/s > > $ sync > > $ dd if=foo of=/dev/null iflag=direct bs=4k > > 1024+0 records in > > 1024+0 records out > > 4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.163079 s, 25.7 MB/s > > > > And you'll get a warning like: > > > > [ 84.896486] ------------[ cut here ]------------ > > [ 84.897370] page offset 94199157981184 != start 0 > > [ 84.898128] WARNING: CPU: 1 PID: 459 at fs/btrfs/inode.c:3119 check_data_csum+0x189/0x260 [btrfs] > > [ 84.899547] Modules linked in: btrfs blake2b_generic xor pata_acpi ata_piix libata scsi_mod raid6_pq virtio_net net_failover virtio_rng libcrc32c rng_core failover > > [ 84.901742] CPU: 1 PID: 459 Comm: kworker/u56:2 Not tainted 5.12.0-rc3-00060-ge0cd3910d8cb-dirty #139 > > [ 84.903205] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 > > [ 84.904875] Workqueue: btrfs-endio btrfs_work_helper [btrfs] > > [ 84.905749] RIP: 0010:check_data_csum+0x189/0x260 [btrfs] > > [ 84.906576] Code: 57 11 00 00 0f 85 03 ff ff ff 4c 89 ca 48 c7 c7 50 ba 35 c0 4c 89 44 24 10 48 89 44 24 08 c6 05 04 57 11 00 01 e8 22 e0 cf d4 <0f> 0b 4c 8b 44 24 10 48 8b 44 24 08 e9 d2 fe ff ff 41 8b 45 00 4d > > [ 84.909288] RSP: 0018:ffffb6e9c164bb98 EFLAGS: 00010282 > > [ 84.910061] RAX: 0000000000000000 RBX: ffffe96b84a05f40 RCX: 0000000000000001 > > [ 84.911109] RDX: 0000000080000001 RSI: ffffffff9573d067 RDI: 00000000ffffffff > > [ 84.912149] RBP: 0000000000000000 R08: 0000000000000000 R09: c0000000ffffdfff > > [ 84.913197] R10: 0000000000000001 R11: ffffb6e9c164b9c0 R12: 0000000000000000 > > [ 84.914247] R13: ffff9d32a28c8dc0 R14: ffff9d32ac495e10 R15: 0000000000000004 > > [ 84.915304] FS: 0000000000000000(0000) GS:ffff9d399f640000(0000) knlGS:0000000000000000 > > [ 84.916478] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 84.917340] CR2: 000055ad52f97120 CR3: 00000001292f4002 CR4: 0000000000370ee0 > > [ 84.918435] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > [ 84.919473] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > [ 84.920515] Call Trace: > > [ 84.920884] ? find_busiest_group+0x41/0x380 > > [ 84.921518] ? load_balance+0x176/0xc10 > > [ 84.922082] ? kvm_sched_clock_read+0x5/0x10 > > [ 84.922711] ? sched_clock+0x5/0x10 > > [ 84.923236] btrfs_end_dio_bio+0x2fb/0x310 [btrfs] > > [ 84.923982] end_workqueue_fn+0x29/0x40 [btrfs] > > [ 84.924698] btrfs_work_helper+0xc1/0x350 [btrfs] > > [ 84.925435] process_one_work+0x1c8/0x390 > > [ 84.926025] ? process_one_work+0x390/0x390 > > [ 84.926650] worker_thread+0x30/0x370 > > [ 84.927209] ? process_one_work+0x390/0x390 > > [ 84.927875] kthread+0x13d/0x160 > > [ 84.928466] ? kthread_park+0x80/0x80 > > [ 84.929008] ret_from_fork+0x22/0x30 > > [ 84.929543] ---[ end trace 4f87c4a13fa476d4 ]--- > > > >>> > >>> Fixes: 265d4ac03fdf ("btrfs: sink parameter start and len to check_data_csum") > >>> Signed-off-by: Omar Sandoval > >>> --- > >>> fs/btrfs/inode.c | 14 +++++++++----- > >>> 1 file changed, 9 insertions(+), 5 deletions(-) > >>> > >>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > >>> index ef6cb7b620d0..d2ece8554416 100644 > >>> --- a/fs/btrfs/inode.c > >>> +++ b/fs/btrfs/inode.c > >>> @@ -2947,11 +2947,13 @@ void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start, > >>> * @bio_offset: offset to the beginning of the bio (in bytes) > >>> * @page: page where is the data to be verified > >>> * @pgoff: offset inside the page > >>> + * @start: logical offset in the file > >> > >> Please add some comment if only for direct IO we need that @start parameter. > > > > Won't that add more confusion? Someone might read that and assume that > > they don't need to pass start for a page cache page. In my opinion, > > having this change in the git log is enough. > > > That's fine. > > Then this patch looks fine to me. > > Reviewed-by: Qu Wenruo Added to misc-next, thanks.