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From: Nick Piggin <npiggin@suse.de>
To: Andrew Morton <akpm@osdl.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
	Linux Filesystems <linux-fsdevel@vger.kernel.org>,
	Nick Piggin <npiggin@suse.de>,
	Linux Memory Management <linux-mm@kvack.org>
Subject: [patch 5/9] mm: debug write deadlocks
Date: Mon, 29 Jan 2007 11:32:24 +0100 (CET)	[thread overview]
Message-ID: <20070129081951.23584.52646.sendpatchset@linux.site> (raw)
In-Reply-To: <20070129081905.23584.97878.sendpatchset@linux.site>

Allow CONFIG_DEBUG_VM to switch off the prefaulting logic, to simulate the
difficult race where the page may be unmapped before calling copy_from_user.
Makes the race much easier to hit.

This is useful for demonstration and testing purposes, but is removed in a
subsequent patch.

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c
+++ linux-2.6/mm/filemap.c
@@ -1894,6 +1894,7 @@ generic_file_buffered_write(struct kiocb
 		if (maxlen > bytes)
 			maxlen = bytes;
 
+#ifndef CONFIG_DEBUG_VM
 		/*
 		 * Bring in the user page that we will copy from _first_.
 		 * Otherwise there's a nasty deadlock on copying from the
@@ -1901,6 +1902,7 @@ generic_file_buffered_write(struct kiocb
 		 * up-to-date.
 		 */
 		fault_in_pages_readable(buf, maxlen);
+#endif
 
 		page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
 		if (!page) {

  parent reply	other threads:[~2007-01-29 10:33 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-29 10:31 [patch 0/9] buffered write deadlock fix Nick Piggin
2007-01-29 10:31 ` [patch 1/9] fs: libfs buffered write leak fix Nick Piggin
2007-02-02 23:52   ` Andrew Morton
2007-02-03  1:33     ` Nick Piggin
2007-02-03  1:58       ` Andrew Morton
2007-02-03  2:09         ` Nick Piggin
2007-02-03  2:19           ` Andrew Morton
2007-02-03  2:28             ` Nick Piggin
2007-02-03 17:49       ` Jörn Engel
2007-02-04  3:55         ` Nick Piggin
2007-01-29 10:31 ` [patch 2/9] mm: revert "generic_file_buffered_write(): handle zero length iovec segments" Nick Piggin
2007-01-29 10:32 ` [patch 3/9] mm: revert "generic_file_buffered_write(): deadlock on vectored write" Nick Piggin
2007-01-29 10:32 ` [patch 4/9] mm: generic_file_buffered_write cleanup Nick Piggin
2007-01-29 10:32 ` Nick Piggin [this message]
2007-01-29 10:32 ` [patch 6/9] mm: be sure to trim blocks Nick Piggin
2007-01-29 10:32 ` [patch 7/9] mm: cleanup pagecache insertion operations Nick Piggin
2007-01-29 10:32 ` [patch 8/9] mm: generic_file_buffered_write iovec cleanup Nick Piggin
2007-01-29 10:33 ` [patch 9/9] mm: fix pagecache write deadlocks Nick Piggin
2007-01-29 11:11   ` Nick Piggin
2007-02-02 23:53   ` Andrew Morton
2007-02-03  1:38     ` Nick Piggin
2007-01-30 20:55 ` [patch 0/9] buffered write deadlock fix Andrew Morton
2007-01-30 23:21   ` Andrew Morton
2007-01-31  1:31     ` Nick Piggin
2007-01-31  0:32   ` Nick Piggin
2007-02-02 23:52 ` Andrew Morton
2007-02-03  1:22   ` Nick Piggin
2007-02-03  6:43   ` Suparna Bhattacharya
     [not found]   ` <370516630.03363@ustc.edu.cn>
2007-02-03 15:31     ` Fengguang Wu
2007-02-04  8:49 Nick Piggin
2007-02-04  8:50 ` [patch 5/9] mm: debug write deadlocks Nick Piggin

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