From: Matthew Wilcox <willy@infradead.org>
To: Dave Chinner <david@fromorbit.com>
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
Subject: Re: [PATCH] iomap: Handle I/O errors gracefully in page_mkwrite
Date: Thu, 4 Jun 2020 16:05:19 -0700 [thread overview]
Message-ID: <20200604230519.GW19604@bombadil.infradead.org> (raw)
In-Reply-To: <20200604225726.GU2040@dread.disaster.area>
On Fri, Jun 05, 2020 at 08:57:26AM +1000, Dave Chinner wrote:
> On Thu, Jun 04, 2020 at 01:23:40PM -0700, Matthew Wilcox wrote:
> > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> >
> > Test generic/019 often results in:
> >
> > WARNING: at fs/iomap/buffered-io.c:1069 iomap_page_mkwrite_actor+0x57/0x70
> >
> > Since this can happen due to a storage error, we should not WARN for it.
> > Just return -EIO, which will be converted to a SIGBUS for the hapless
> > task attempting to write to the page that we can't read.
>
> Why didn't the "read" part of the fault which had the EIO error fail
> the page fault? i.e. why are we waiting until deep inside the write
> fault path to error out on a failed page read?
I have a hypothesis that I don't know how to verify.
First the task does a load from the page and we put a read-only PTE in
the page tables. Then it writes to the page using write(). The page
gets written back, but hits an error in iomap_writepage_map()
which calls ClearPageUptodate(). Then the task with it mapped attempts
to store to it.
I haven't dug through what generic/019 does, so I don't know how plausible
this is.
next prev parent reply other threads:[~2020-06-04 23:12 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-04 20:23 [PATCH] iomap: Handle I/O errors gracefully in page_mkwrite Matthew Wilcox
2020-06-04 22:57 ` Dave Chinner
2020-06-04 23:05 ` Matthew Wilcox [this message]
2020-06-04 23:30 ` Dave Chinner
2020-06-04 23:50 ` Matthew Wilcox
2020-06-05 0:31 ` Dave Chinner
2020-06-05 2:24 ` Matthew Wilcox
2020-06-05 3:07 ` Dave Chinner
2020-06-05 12:48 ` Matthew Wilcox
2020-06-05 16:18 ` Darrick J. Wong
2020-06-05 21:48 ` Dave Chinner
2020-06-05 22:49 ` Matthew Wilcox
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