From: Miklos Szeredi <miklos@szeredi.hu>
To: akpm@linux-foundation.org, torvalds@linux-foundation.org
Cc: npiggin@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [patch] mm: fix infinite loop in filemap_fault
Date: Thu, 08 May 2008 21:19:45 +0200 [thread overview]
Message-ID: <E1JuBeb-0008Hr-0q@pomaz-ex.szeredi.hu> (raw)
I think this is a pretty obvious fix. The only thing I don't
understand, is how did this manage to go unnoticed for almost a year.
Are persistent read errors *that* rare?
----
From: Miklos Szeredi <mszeredi@suse.cz>
filemap_fault will go into an infinite loop if ->readpage() fails
asynchronously.
AFAICS the bug was introduced by this commit, which removed the wait
after the final readpage:
commit d00806b183152af6d24f46f0c33f14162ca1262a
Author: Nick Piggin <npiggin@suse.de>
Date: Thu Jul 19 01:46:57 2007 -0700
mm: fix fault vs invalidate race for linear mappings
Fix by reintroducing the wait_on_page_locked() after ->readpage() to
make sure the page is up-to-date before jumping back to the beginning
of the function.
I've noticed this while testing nfs exporting on fuse. The patch
fixes it.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: Nick Piggin <npiggin@suse.de>
---
mm/filemap.c | 5 +++++
1 file changed, 5 insertions(+)
Index: linux.git/mm/filemap.c
===================================================================
--- linux.git.orig/mm/filemap.c 2008-05-08 08:17:22.000000000 +0200
+++ linux.git/mm/filemap.c 2008-05-08 11:55:42.000000000 +0200
@@ -1461,6 +1461,11 @@ page_not_uptodate:
*/
ClearPageError(page);
error = mapping->a_ops->readpage(file, page);
+ if (!error) {
+ wait_on_page_locked(page);
+ if (!PageUptodate(page))
+ error = -EIO;
+ }
page_cache_release(page);
if (!error || error == AOP_TRUNCATED_PAGE)
--
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reply other threads:[~2008-05-08 19:19 UTC|newest]
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