Commit c6d119cf authored Sep 09, 2014 by NeilBrown

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



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: 79ef3a8a
cc: stable@vger.kernel.org (v3.13+)
Signed-off-by: NeilBrown <neilb@suse.de>

parent f0cc9a05

drivers/md/raid1.c

+1 −5

Original line number	Diff line number	Diff line
		@@ -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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