From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-f199.google.com (mail-oi1-f199.google.com [209.85.167.199]) by kanga.kvack.org (Postfix) with ESMTP id 0088B8E0038 for ; Tue, 8 Jan 2019 05:04:47 -0500 (EST) Received: by mail-oi1-f199.google.com with SMTP id a62so1493694oii.23 for ; Tue, 08 Jan 2019 02:04:46 -0800 (PST) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id g5si380445otn.228.2019.01.08.02.04.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Jan 2019 02:04:45 -0800 (PST) Subject: Re: INFO: task hung in generic_file_write_iter References: <0000000000009ce88d05714242a8@google.com> <4b349bff-8ad4-6410-250d-593b13d8d496@I-love.SAKURA.ne.jp> <9b9fcdda-c347-53ee-fdbb-8a7d11cf430e@I-love.SAKURA.ne.jp> <20180720130602.f3d6dc4c943558875a36cb52@linux-foundation.org> <20180806100928.x7anab3c3y5q4ssa@quack2.suse.cz> <20190102144015.GA23089@quack2.suse.cz> <275523c6-f750-44c2-a8a4-f3825eeab788@i-love.sakura.ne.jp> <20190102172636.GA29127@quack2.suse.cz> From: Tetsuo Handa Message-ID: Date: Tue, 8 Jan 2019 19:04:06 +0900 MIME-Version: 1.0 In-Reply-To: <20190102172636.GA29127@quack2.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Andrew Morton , Alexander Viro , syzbot , linux-mm@kvack.org, mgorman@techsingularity.net, Michal Hocko , ak@linux.intel.com, jlayton@redhat.com, linux-kernel@vger.kernel.org, mawilcox@microsoft.com, syzkaller-bugs@googlegroups.com, tim.c.chen@linux.intel.com, linux-fsdevel On 2019/01/03 2:26, Jan Kara wrote: > On Thu 03-01-19 01:07:25, Tetsuo Handa wrote: >> On 2019/01/02 23:40, Jan Kara wrote: >>> I had a look into this and the only good explanation for this I have is >>> that sb->s_blocksize is different from (1 << sb->s_bdev->bd_inode->i_blkbits). >>> If that would happen, we'd get exactly the behavior syzkaller observes >>> because grow_buffers() would populate different page than >>> __find_get_block() then looks up. >>> >>> However I don't see how that's possible since the filesystem has the block >>> device open exclusively and blkdev_bszset() makes sure we also have >>> exclusive access to the block device before changing the block device size. >>> So changing block device block size after filesystem gets access to the >>> device should be impossible. >>> >>> Anyway, could you perhaps add to your debug patch a dump of 'size' passed >>> to __getblk_slow() and bdev->bd_inode->i_blkbits? That should tell us >>> whether my theory is right or not. Thanks! >>> Got two reports. 'size' is 512 while bdev->bd_inode->i_blkbits is 12. https://syzkaller.appspot.com/text?tag=CrashLog&x=1237c3ab400000 [ 385.723941][ T439] kworker/u4:3(439): getblk(): executed=9 bh_count=0 bh_state=0 bdev_super_blocksize=512 size=512 bdev_super_blocksize_bits=9 bdev_inode_blkbits=12 (...snipped...) [ 568.159544][ T439] kworker/u4:3(439): getblk(): executed=9 bh_count=0 bh_state=0 bdev_super_blocksize=512 size=512 bdev_super_blocksize_bits=9 bdev_inode_blkbits=12 https://syzkaller.appspot.com/text?tag=CrashLog&x=143383d7400000 [ 1355.681513][ T6893] syz-executor0(6893): getblk(): executed=9 bh_count=0 bh_state=0 bdev_super_blocksize=512 size=512 bdev_super_blocksize_bits=9 bdev_inode_blkbits=12 [ 1358.274585][T15649] kworker/u4:17(15649): getblk(): executed=9 bh_count=0 bh_state=0 bdev_super_blocksize=512 size=512 bdev_super_blocksize_bits=9 bdev_inode_blkbits=12 (...snipped...) [ 1455.341572][ T6893] syz-executor0(6893): getblk(): executed=9 bh_count=0 bh_state=0 bdev_super_blocksize=512 size=512 bdev_super_blocksize_bits=9 bdev_inode_blkbits=12 [ 1455.541457][T15649] kworker/u4:17(15649): getblk(): executed=9 bh_count=0 bh_state=0 bdev_super_blocksize=512 size=512 bdev_super_blocksize_bits=9 bdev_inode_blkbits=12 >> >> OK. Andrew, will you add (or fold into) this change? >> >> From e6f334380ad2c87457bfc2a4058316c47f75824a Mon Sep 17 00:00:00 2001 >> From: Tetsuo Handa >> Date: Thu, 3 Jan 2019 01:03:35 +0900 >> Subject: [PATCH] fs/buffer.c: dump more info for __getblk_gfp() stall problem >> >> We need to dump more variables on top of >> "fs/buffer.c: add debug print for __getblk_gfp() stall problem". >> >> Signed-off-by: Tetsuo Handa >> Cc: Jan Kara >> --- >> fs/buffer.c | 9 +++++++-- >> 1 file changed, 7 insertions(+), 2 deletions(-) >> >> diff --git a/fs/buffer.c b/fs/buffer.c >> index 580fda0..a50acac 100644 >> --- a/fs/buffer.c >> +++ b/fs/buffer.c >> @@ -1066,9 +1066,14 @@ static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size) >> #ifdef CONFIG_DEBUG_AID_FOR_SYZBOT >> if (!time_after(jiffies, current->getblk_stamp + 3 * HZ)) >> continue; >> - printk(KERN_ERR "%s(%u): getblk(): executed=%x bh_count=%d bh_state=%lx\n", >> + printk(KERN_ERR "%s(%u): getblk(): executed=%x bh_count=%d bh_state=%lx " >> + "bdev_super_blocksize=%lu size=%u " >> + "bdev_super_blocksize_bits=%u bdev_inode_blkbits=%u\n", >> current->comm, current->pid, current->getblk_executed, >> - current->getblk_bh_count, current->getblk_bh_state); >> + current->getblk_bh_count, current->getblk_bh_state, >> + bdev->bd_super->s_blocksize, size, >> + bdev->bd_super->s_blocksize_bits, >> + bdev->bd_inode->i_blkbits); > > Well, bd_super may be NULL if there's no filesystem mounted so it would be > safer to check for this rather than blindly dereferencing it... Otherwise > the change looks good to me. > > Honza >