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13 June 2022, 11:31:42 UTC
Revision d1901ef099c38afd11add4cfb3312c02ef21ec4a authored by Tomáš Hodek on 23 February 2015, 00:00:38 UTC, committed by NeilBrown on 25 February 2015, 00:37:02 UTC 
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+)
1 parent c517d83
History
Tip revision: d1901ef099c38afd11add4cfb3312c02ef21ec4a authored by Tomáš Hodek on 23 February 2015, 00:00:38 UTC
md/raid1: fix read balance when a drive is write-mostly.
Tip revision: d1901ef
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