linux-kernel - Re: [PATCH] mm: fix page_mkclean

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Date:	Wed, 27 Dec 2006 21:32:00 -0700
From:	"Gordon Farquharson" <gordonfarquharson@...il.com>
To:	"Linus Torvalds" <torvalds@...l.org>
Cc:	"David Miller" <davem@...emloft.net>, ranma@...edrich.de,
	tbm@...ius.com, "Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	andrei.popa@...eo.ro, "Andrew Morton" <akpm@...l.org>,
	hugh@...itas.com, nickpiggin@...oo.com.au, arjan@...radead.org,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: fix page_mkclean_one

On 12/27/06, Linus Torvalds <torvalds@...l.org> wrote:

> [ Modified test-program that tells you where the corruption happens (and
>   when the missing parts were supposed to be written out) appended, in
>   case people care. ]

For the record, this is the output from a run on our ARM machine (32
MB RAM) with 2.6.18 + the following patches:

   mm: tracking shared dirty pages
   mm: balance dirty pages
   mm: optimize the new mprotect() code a bit
   mm: small cleanup of install_page()
   mm: fixup do_wp_page()
   mm: msync() cleanup

It is at all suprising that the second offset within a page can be
less than the first offset within a page ? e.g.

Chunk 260 corrupted (1-1455)  (2769-127)

$ ./linus-test
Writing chunk 279/280 (99%)
Chunk 256 corrupted (1-1455)  (1025-2479)
Expected 0, got 1
Written as (82)175(56)
Chunk 258 corrupted (1-1455)  (3945-1303)
Expected 2, got 3
Written as (56)51(20)
Chunk 260 corrupted (1-1455)  (2769-127)
Expected 4, got 5
Written as (20)30(18)
Chunk 262 corrupted (1-1455)  (1593-3047)
Expected 6, got 7
Written as (18)196(158)
Chunk 264 corrupted (1-1455)  (417-1871)
Expected 8, got 9
Written as (158)133(146)
Chunk 266 corrupted (1-1455)  (3337-695)
Expected 10, got 11
Written as (146)43(77)
Chunk 268 corrupted (1-1455)  (2161-3615)
Expected 12, got 13
Written as (77)251(211)
Chunk 270 corrupted (1-1455)  (985-2439)
Expected 14, got 15
Written as (211)257(231)
Chunk 272 corrupted (1-1455)  (3905-1263)
Expected 16, got 17
Written as (231)254(154)
Chunk 274 corrupted (1-1455)  (2729-87)
Expected 18, got 19
Written as (154)11(85)
Chunk 276 corrupted (1-1455)  (1553-3007)
Expected 20, got 21
Written as (85)230(134)
Chunk 278 corrupted (1-1455)  (377-1831)
Expected 22, got 23
Written as (134)233(103)
Checking chunk 279/280 (99%)

Gordon

-- 
Gordon Farquharson
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