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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 14:40:53 -0800 |
| commit | b581e762b1a452ac94d452117a6c953f4d011767 (patch) | |
| tree | bfaa0d05b640d08e5501854e69cbb0ba2cc799e5 /drivers | |
| parent | 58f0e96a4358f164f3857ee0d609d1b75a3ccf7d (diff) | |
| download | lwn-b581e762b1a452ac94d452117a6c953f4d011767.tar.gz lwn-b581e762b1a452ac94d452117a6c953f4d011767.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>
Diffstat (limited to 'drivers')
| -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 e885dbf08c40..86ac4a4ccc01 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -557,7 +557,7 @@ 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) @@ -566,7 +566,8 @@ 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; } |