Date: Tue, 23 Mar 2004 01:25:14 -0800
From: Andrew Morton <akpm@osdl.org>
To: Daniel McNeil <daniel@osdl.org>
Cc: mason@suse.com, linux-kernel@vger.kernel.org, linux-aio@kvack.org
Subject: Re: 2.6.5-rc1-mm2 and direct_read_under and wb
Message-Id: <20040323012514.7670f622.akpm@osdl.org>
In-Reply-To: <1080003067.6930.78.camel@ibm-c.pdx.osdl.net>
References: <20040314172809.31bd72f7.akpm@osdl.org>
	<20040317123324.46411197.akpm@osdl.org>
	<1079563568.4185.1947.camel@watt.suse.com>
	<20040317150909.7fd121bd.akpm@osdl.org>
	<1079566076.4186.1959.camel@watt.suse.com>
	<20040317155111.49d09a87.akpm@osdl.org>
	<1079568387.4186.1964.camel@watt.suse.com>
	<20040317161338.28b21c35.akpm@osdl.org>
	<1079569870.4186.1967.camel@watt.suse.com>
	<20040317163332.0385d665.akpm@osdl.org>
	<1079572511.6930.5.camel@ibm-c.pdx.osdl.net>
	<1079632431.6930.30.camel@ibm-c.pdx.osdl.net>
	<1079635678.4185.2100.camel@watt.suse.com>
	<1079637004.6930.42.camel@ibm-c.pdx.osdl.net>
	<1079714990.6930.49.camel@ibm-c.pdx.osdl.net>
	<1079715901.6930.52.camel@ibm-c.pdx.osdl.net>
	<1079879799.11062.348.camel@watt.suse.com>
	<1079979016.6930.62.camel@ibm-c.pdx.osdl.net>
	<1079980512.11058.524.camel@watt.suse.com>
	<1079981473.6930.71.camel@ibm-c.pdx.osdl.net>
	<20040322151312.6b629736.akpm@osdl.org>
	<1080003067.6930.78.camel@ibm-c.pdx.osdl.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1708
Lines: 48

Daniel McNeil <daniel@osdl.org> wrote:
>
> The test has been running over 5 hours now without seeing uninitialized
>  data.  I'll let it run overnight, but it looks like the small 
>  __block_write_full_page patch fixes the problem.

OK, thanks.  It does cause gargantuan amounts of CPU consumption as
expected.  The below version fixes that up.  I'm not 100% happy with it,
but it seems OK on the profiles.


diff -puN fs/buffer.c~block_write_full_page-redirty fs/buffer.c
--- 25/fs/buffer.c~block_write_full_page-redirty	2004-03-23 01:06:59.281253176 -0800
+++ 25-akpm/fs/buffer.c	2004-03-23 01:09:11.313181272 -0800
@@ -1810,14 +1810,18 @@ static int __block_write_full_page(struc
 		get_bh(bh);
 		if (!buffer_mapped(bh))
 			continue;
-		if (wbc->sync_mode != WB_SYNC_NONE) {
+		/*
+		 * If it's a fully non-blocking write attempt and we cannot
+		 * lock the buffer then redirty the page.  Note that this can
+		 * potentially cause a busy-wait loop from pdflush and kswapd
+		 * activity, but those code paths have their own higher-level
+		 * throttling.
+		 */
+		if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
 			lock_buffer(bh);
-		} else {
-			if (test_set_buffer_locked(bh)) {
-				if (buffer_dirty(bh))
-					__set_page_dirty_nobuffers(page);
-				continue;
-			}
+		} else if (test_set_buffer_locked(bh)) {
+			__set_page_dirty_nobuffers(page);
+			continue;
 		}
 		if (test_clear_buffer_dirty(bh)) {
 			if (!buffer_uptodate(bh))

_

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/