From: Qian Cai <cai@lca.pw>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
linux-mm@kvack.org
Subject: Re: kernel BUG at mm/page-writeback.c:2241 [ BUG_ON(PageWriteback(page); ]
Date: Thu, 22 Oct 2020 11:35:26 -0400 [thread overview]
Message-ID: <7ec15e2710db02be81a6c47afc57abed4bf8016c.camel@lca.pw> (raw)
In-Reply-To: <20201022004906.GQ20115@casper.infradead.org>
On Thu, 2020-10-22 at 01:49 +0100, Matthew Wilcox wrote:
> On Wed, Oct 21, 2020 at 08:30:18PM -0400, Qian Cai wrote:
> > Today's linux-next starts to trigger this wondering if anyone has any clue.
>
> I've seen that occasionally too. I changed that BUG_ON to VM_BUG_ON_PAGE
> to try to get a clue about it. Good to know it's not the THP patches
> since they aren't in linux-next.
>
> I don't understand how it can happen. We have the page locked, and then we
> do:
>
> if (PageWriteback(page)) {
> if (wbc->sync_mode != WB_SYNC_NONE)
> wait_on_page_writeback(page);
> else
> goto continue_unlock;
> }
>
> VM_BUG_ON_PAGE(PageWriteback(page), page);
>
> Nobody should be able to put this page under writeback while we have it
> locked ... right? The page can be redirtied by the code that's supposed
> to be writing it back, but I don't see how anyone can make PageWriteback
> true while we're holding the page lock.
It happened again on today's linux-next:
[ 7613.579890][T55770] page:00000000a4b35e02 refcount:3 mapcount:0 mapping:00000000457ceb87 index:0x3e pfn:0x1cef4e
[ 7613.590594][T55770] aops:xfs_address_space_operations ino:805d85a dentry name:"doio.f1.55762"
[ 7613.599192][T55770] flags: 0xbfffc0000000bf(locked|waiters|referenced|uptodate|dirty|lru|active)
[ 7613.608596][T55770] raw: 00bfffc0000000bf ffffea0005027d48 ffff88810eaec030 ffff888231f3a6a8
[ 7613.617101][T55770] raw: 000000000000003e 0000000000000000 00000003ffffffff ffff888143724000
[ 7613.625590][T55770] page dumped because: VM_BUG_ON_PAGE(PageWriteback(page))
[ 7613.632695][T55770] page->mem_cgroup:ffff888143724000
next prev parent reply other threads:[~2020-10-22 15:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-22 0:30 kernel BUG at mm/page-writeback.c:2241 [ BUG_ON(PageWriteback(page); ] Qian Cai
2020-10-22 0:49 ` Matthew Wilcox
2020-10-22 13:23 ` William Kucharski
2020-10-22 16:46 ` Matthew Wilcox
2020-10-22 15:35 ` Qian Cai [this message]
2020-10-22 17:12 ` Matthew Wilcox
2020-10-30 12:08 ` Qian Cai
2020-10-26 9:49 ` Jan Kara
2020-10-26 13:13 ` Matthew Wilcox
2020-10-26 13:55 ` Jens Axboe
2020-10-26 14:26 ` Qian Cai
2020-11-04 15:16 ` Jan Kara
2020-11-04 15:40 ` Qian Cai
2020-10-26 14:51 ` Qian Cai
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