From: Nick Piggin <npiggin@suse.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: hugh.dickins@tiscali.co.uk, riel@redhat.com,
chris.mason@oracle.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
fengguang.wu@intel.com, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v5
Date: Tue, 9 Jun 2009 13:14:32 +0200 [thread overview]
Message-ID: <20090609111432.GL14820@wotan.suse.de> (raw)
In-Reply-To: <20090609095155.GA14820@wotan.suse.de>
On Tue, Jun 09, 2009 at 11:51:55AM +0200, Nick Piggin wrote:
> On Wed, Jun 03, 2009 at 08:46:47PM +0200, Andi Kleen wrote:
> > +static int me_pagecache_clean(struct page *p, unsigned long pfn)
> > +{
> > + struct address_space *mapping;
> > +
> > + if (!isolate_lru_page(p))
> > + page_cache_release(p);
> > +
> > + /*
> > + * Now truncate the page in the page cache. This is really
> > + * more like a "temporary hole punch"
> > + * Don't do this for block devices when someone else
> > + * has a reference, because it could be file system metadata
> > + * and that's not safe to truncate.
> > + */
> > + mapping = page_mapping(p);
> > + if (mapping && S_ISBLK(mapping->host->i_mode) && page_count(p) > 1) {
> > + printk(KERN_ERR
> > + "MCE %#lx: page looks like a unsupported file system metadata page\n",
> > + pfn);
> > + return FAILED;
> > + }
>
> page_count check is racy. Hmm, S_ISBLK should handle xfs's private mapping.
> AFAIK btrfs has a similar private mapping but a quick grep does not show
> up S_IFBLK anywhere, so I don't know what the situation is there.
>
> Unfortunately though, the linear mapping is not the only metadata mapping
> a filesystem might have. Many work on directories in seperate mappings
> (ext2, for example, which is where I first looked and will still oops with
> your check).
>
> Also, others may have other interesting inodes they use for metadata. Do
> any of them go through the pagecache? I dont know. The ext3 journal,
> for example? How does that work?
>
> Unfortunately I don't know a good way to detect regular data mappings
> easily. Ccing linux-fsdevel. Until that is worked out, you'd need to
> use the safe pagecache invalidate rather than unsafe truncate.
Maybe just testing S_ISREG would be better. Definitely safer than
ISBLK.
Note that for !ISREG files, then you can still attempt the
non-destructive invalidate (after extracting a suitable function
similarly to the truncate one). Most likely the fs is not using
the page right now, so it should give bit more coverage.
I still don't exactly know about, say, ext3 journal. Probably
it doesn't use pagecache anyway. Do any other filesystems do
crazy things with S_ISREG files? They probably deserve to oops
if they do ;)
prev parent reply other threads:[~2009-06-09 11:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20090603846.816684333@firstfloor.org>
[not found] ` <20090603184648.2E2131D028F@basil.firstfloor.org>
2009-06-09 9:51 ` [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v5 Nick Piggin
2009-06-09 11:14 ` Nick Piggin [this message]
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