From: Matthew Wilcox <willy@infradead.org>
To: Qian Cai <cai@lca.pw>
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 01:49:06 +0100 [thread overview]
Message-ID: <20201022004906.GQ20115@casper.infradead.org> (raw)
In-Reply-To: <645a3f332f37e09057c10bc32f4f298ce56049bb.camel@lca.pw>
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.
next parent reply other threads:[~2020-10-22 0:49 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <645a3f332f37e09057c10bc32f4f298ce56049bb.camel@lca.pw>
2020-10-22 0:49 ` Matthew Wilcox [this message]
2020-10-22 13:23 ` kernel BUG at mm/page-writeback.c:2241 [ BUG_ON(PageWriteback(page); ] William Kucharski
2020-10-22 16:46 ` Matthew Wilcox
[not found] ` <7ec15e2710db02be81a6c47afc57abed4bf8016c.camel@lca.pw>
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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