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| author | Tomáš Hodek <tomas.hodek@volny.cz> | 2015-02-23 11:00:38 +1100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-03-06 14:53:05 -0800 |
| commit | 177f6a7ea9cca89e71e0c5771ce237998299f0e3 (patch) | |
| tree | 8092bfabeac3c80eb07a6a96a8371d0f92ebefcb | |
| parent | dbf3bbd13627dd640276a298012a22373ccf7bd1 (diff) | |
| download | lwn-177f6a7ea9cca89e71e0c5771ce237998299f0e3.tar.gz lwn-177f6a7ea9cca89e71e0c5771ce237998299f0e3.zip | |
md/raid1: fix read balance when a drive is write-mostly.
commit d1901ef099c38afd11add4cfb3312c02ef21ec4a upstream.
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/md/raid1.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 40b35be34f8d..2f2f38f4d83c 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; } |