All of lore.kernel.org
 help / color / mirror / Atom feed
From: Andrew Morton <akpm@linux-foundation.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	Kent Overstreet <kent.overstreet@gmail.com>,
	Christoph Hellwig <hch@lst.de>
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: <20210303121253.9f44d8129f148b1e2e78cc81@linux-foundation.org> (raw)
In-Reply-To: <20210303132640.GB2723601@casper.infradead.org>

On Wed, 3 Mar 2021 13:26:40 +0000 Matthew Wilcox <willy@infradead.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 <akpm@osdl.org>
> 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210303121253.9f44d8129f148b1e2e78cc81@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=hch@lst.de \
    --cc=kent.overstreet@gmail.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=willy@infradead.org \
    --subject='Re: [PATCH] mm/filemap: Use filemap_read_page in filemap_fault' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.