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authorTomáš Hodek <tomas.hodek@volny.cz>2015-02-23 11:00:38 +1100
committerNeilBrown <neilb@suse.de>2015-02-25 11:37:02 +1100
commitd1901ef099c38afd11add4cfb3312c02ef21ec4a (patch)
tree75becab74c257df726f895e5dc477f2883cd34b9 /drivers/md/raid1.c
parentc517d838eb7d07bbe9507871fab3931deccff539 (diff)
md/raid1: fix read balance when a drive is write-mostly.
When a drive is marked write-mostly it should only be the target of reads if there is no other option. This behaviour was broken by commit 9dedf60313fa4dddfd5b9b226a0ef12a512bf9dc md/raid1: read balance chooses idlest disk for SSD which causes a write-mostly device to be *preferred* is some cases. Restore correct behaviour by checking and setting best_dist_disk and best_pending_disk rather than best_disk. We only need to test one of these as they are both changed from -1 or >=0 at the same time. As we leave min_pending and best_dist unchanged, any non-write-mostly device will appear better than the write-mostly device. Reported-by: Tomáš Hodek <tomas.hodek@volny.cz> Reported-by: Dark Penguin <darkpenguin@yandex.ru> Signed-off-by: NeilBrown <neilb@suse.de> Link: http://marc.info/?l=linux-raid&m=135982797322422 Fixes: 9dedf60313fa4dddfd5b9b226a0ef12a512bf9dc Cc: stable@vger.kernel.org (3.6+)
Diffstat (limited to 'drivers/md/raid1.c')
-rw-r--r--drivers/md/raid1.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 4153da5d4011..d34e238afa54 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -560,7 +560,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
if (test_bit(WriteMostly, &rdev->flags)) {
/* Don't balance among write-mostly, just
* use the first as a last resort */
- if (best_disk < 0) {
+ if (best_dist_disk < 0) {
if (is_badblock(rdev, this_sector, sectors,
&first_bad, &bad_sectors)) {
if (first_bad < this_sector)
@@ -569,7 +569,8 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
best_good_sectors = first_bad - this_sector;
} else
best_good_sectors = sectors;
- best_disk = disk;
+ best_dist_disk = disk;
+ best_pending_disk = disk;
}
continue;
}