linux-kernel - [086/200] md: Fix read balancing in RAID1 and RAID10 on drives

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Message-Id: <20100701174253.691749866@clark.site>
Date:	Thu, 01 Jul 2010 10:42:56 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	NeilBrown <neilb@...e.de>
Subject: [086/200] md: Fix read balancing in RAID1 and RAID10 on drives > 2TB

2.6.34-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@...e.de>

commit af3a2cd6b8a479345786e7fe5e199ad2f6240e56 upstream.

read_balance uses a "unsigned long" for a sector number which
will get truncated beyond 2TB.
This will cause read-balancing to be non-optimal, and can cause
data to be read from the 'wrong' branch during a resync.  This has a
very small chance of returning wrong data.

Reported-by: Jordan Russell <jr-list-2010@....to>
Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/md/raid1.c  |    4 ++--
 drivers/md/raid10.c |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -418,7 +418,7 @@ static void raid1_end_write_request(stru
  */
 static int read_balance(conf_t *conf, r1bio_t *r1_bio)
 {
-	const unsigned long this_sector = r1_bio->sector;
+	const sector_t this_sector = r1_bio->sector;
 	int new_disk = conf->last_used, disk = new_disk;
 	int wonly_disk = -1;
 	const int sectors = r1_bio->sectors;
@@ -434,7 +434,7 @@ static int read_balance(conf_t *conf, r1
  retry:
 	if (conf->mddev->recovery_cp < MaxSector &&
 	    (this_sector + sectors >= conf->next_resync)) {
-		/* Choose the first operation device, for consistancy */
+		/* Choose the first operational device, for consistancy */
 		new_disk = 0;
 
 		for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -494,7 +494,7 @@ static int raid10_mergeable_bvec(struct
  */
 static int read_balance(conf_t *conf, r10bio_t *r10_bio)
 {
-	const unsigned long this_sector = r10_bio->sector;
+	const sector_t this_sector = r10_bio->sector;
 	int disk, slot, nslot;
 	const int sectors = r10_bio->sectors;
 	sector_t new_distance, current_distance;


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