[08/23] md: Fix read balancing in RAID1 and RAID10 on drives > 2TB

Greg KH
2010-07-01T18:13:42Z

2.6.27-stable review patch. If anyone has any objections, please let us know.

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

From: NeilBrown <neilb@suse.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@quo.to>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.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
@@ -413,7 +413,7 @@ 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;
@@ -429,7 +429,7 @@ 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
@@ -490,7 +490,7 @@ 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;