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From: Andrew Morton <>
To: Matthew Wilcox <>
	Kent Overstreet <>,
	Christoph Hellwig <>
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: <> (raw)
In-Reply-To: <>

On Wed, 3 Mar 2021 13:26:40 +0000 Matthew Wilcox <> wrote:

> But here's the thing ... invalidate_mapping_pages() doesn't
> ClearPageUptodate.  The only places where we ClearPageUptodate is on an
> I/O error.


> 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 <>
> 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.

  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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