Commit dd777df4 authored by NeilBrown's avatar NeilBrown Committed by Greg Kroah-Hartman

md/raid1: be more cautious where we read-balance during resync.

commit c6d119cf upstream.

commit 79ef3a8a made
it possible for reads to happen concurrently with resync.
This means that we need to be more careful where read_balancing
is allowed during resync - we can no longer be sure that any
resync that has already started will definitely finish.

So keep read_balancing to before recovery_cp, which is conservative
but safe.

This bug makes it possible to read from a device that doesn't
have up-to-date data, so it can cause data corruption.
So it is suitable for any kernel since 3.11.

Fixes: 79ef3a8aSigned-off-by: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3ab661d9
......@@ -540,11 +540,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
has_nonrot_disk = 0;
choose_next_idle = 0;
if (conf->mddev->recovery_cp < MaxSector &&
(this_sector + sectors >= conf->next_resync))
choose_first = 1;
else
choose_first = 0;
choose_first = (conf->mddev->recovery_cp < this_sector + sectors);
for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
sector_t dist;
......
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