From: Andrew Morton <email@example.com> To: Matthew Wilcox <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.org, Kent Overstreet <email@example.com>, Christoph Hellwig <firstname.lastname@example.org> Subject: Re: [PATCH] mm/filemap: Use filemap_read_page in filemap_fault Date: Wed, 3 Mar 2021 12:12:53 -0800 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <20210303132640.GB2723601@casper.infradead.org> On Wed, 3 Mar 2021 13:26:40 +0000 Matthew Wilcox <firstname.lastname@example.org> wrote: > But here's the thing ... invalidate_mapping_pages() doesn't > ClearPageUptodate. The only places where we ClearPageUptodate is on an > I/O error. yup. > So ... as far as I can tell, the only way to hit this is: > > - Get an I/O error during the wait > - Have another thread cause the page to be removed from the page cache > (eg do direct I/O to the file) before this thread is run. > > and the consequence to this change is that we have another attempt to > read the page instead of returning an error immediately. I'm OK with > that unintentional change, although I think the previous behaviour was > also perfectly acceptable (after all, there was an I/O error while trying > to read this page). > > Delving into the linux-fullhistory tree, this code was introduced by ... > > commit 56f0d5fe6851037214a041a5cb4fc66199256544 > Author: Andrew Morton <email@example.com> > Date: Fri Jan 7 22:03:01 2005 -0800 > > [PATCH] readpage-vs-invalidate fix > > A while ago we merged a patch which tried to solve a problem wherein a > concurrent read() and invalidate_inode_pages() would cause the read() to > return -EIO because invalidate cleared PageUptodate() at the wrong time. > > We no longer clear PageUptodate, so I think this is stale code? Perhaps > you could check with the original author ... Which code do you think might be stale? We need the !PageUptodate check to catch IO errors and we need the !page->mapping check to catch invalidates. Am a bit confused.
next prev parent reply other threads:[~2021-03-04 0:21 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-02-26 14:00 Matthew Wilcox (Oracle) 2021-03-03 1:30 ` Andrew Morton 2021-03-03 1:33 ` Matthew Wilcox 2021-03-03 6:07 ` Andrew Morton 2021-03-03 13:26 ` Matthew Wilcox 2021-03-03 20:12 ` Andrew Morton [this message] 2021-03-03 20:57 ` Matthew Wilcox 2021-03-03 21:51 ` Andrew Morton 2021-03-03 22:31 ` Matthew Wilcox
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