linux-kernel - [PATCH 1/1] um: ubd: Fix data corruption

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Date:	Tue, 28 Sep 2010 23:47:36 +0200
From:	Richard Weinberger <richard@....at>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, jdike@...toit.com,
	user-mode-linux-devel@...ts.sourceforge.net,
	user-mode-linux-user@...ts.sourceforge.net, janjaap@....nl,
	geert@...ux-m68k.org, jaxboe@...ionio.com,
	martin.petersen@...cle.com, adobriyan@...il.com,
	cdfrey@...rsquare.net, Richard Weinberger <richard@....at>
Subject: [PATCH 1/1] um: ubd: Fix data corruption

Under high load the file system gets corrupted.
This patch fixes the issue.

Many thanks to Janjaap Bos <janjaap@....nl>!

LKML-Reference: <AANLkTi=PTp7YW_eYxtF-H2QSxgei3whWH59wU0C9oCkz () mail ! gmail ! com>
Signed-off-by: Richard Weinberger <richard@....at>
---
 arch/um/drivers/ubd_kern.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 1bcd208..2874b83 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -748,9 +748,12 @@ static int ubd_open_dev(struct ubd *ubd_dev)
 	}
 	ubd_dev->fd = fd;
 
-	if(ubd_dev->cow.file != NULL){
-		blk_queue_max_hw_sectors(ubd_dev->queue, 8 * sizeof(long));
+	/* A setting higher than 1 sector currently (>= v2.6.31) generates
+		data loss, both for raw and cow ubd. */
+	blk_queue_max_hw_sectors(ubd_dev->queue, 1 * sizeof(long));
+	blk_queue_max_segments(ubd_dev->queue, 1 * sizeof(long));
 
+	if (ubd_dev->cow.file != NULL) {
 		err = -ENOMEM;
 		ubd_dev->cow.bitmap = vmalloc(ubd_dev->cow.bitmap_len);
 		if(ubd_dev->cow.bitmap == NULL){
-- 
1.6.6.1

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