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dm raid: add discard support for RAID levels 4, 5 and 6 

In case of RAID levels 4, 5 and 6 we have to verify each RAID members'
ability to zero data on discards to avoid stripe data corruption -- if
discard_zeroes_data is not set for each RAID member discard support must
be disabled.  But given the uncertainty of whether or not a RAID member
properly supports zeroing data on discard we require the user to
explicitly allow discard support on RAID levels 4, 5, and 6 by setting
a dm-raid module paramter, e.g.: dm-raid.devices_handle_discard_safely=Y
Otherwise, discards could cause data corruption on RAID4/5/6.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Heinz Mauelshagen 2014-09-24 17:47:19 +02:00 committed by Mike Snitzer
parent 75b8e04bbf
commit 48cf06bc5f
1 changed files with 34 additions and 4 deletions
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38
drivers/md/dm-raid.c
View File

@ -18,6 +18,8 @@
#define DM_MSG_PREFIX "raid"
static bool devices_handle_discard_safely = false;
/*
* The following flags are used by dm-raid.c to set up the array state.
* They must be cleared before md_run is called.
@ -475,6 +477,8 @@ too_many:
* will form the "stripe"
* [[no]sync] Force or prevent recovery of the
* entire array
* [devices_handle_discard_safely] Allow discards on RAID4/5/6; useful if RAID
* member device(s) properly support TRIM/UNMAP
* [rebuild <idx>] Rebuild the drive indicated by the index
* [daemon_sleep <ms>] Time between bitmap daemon work to
* clear bits
@ -1150,23 +1154,45 @@ static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
}
/*
* Enable/disable discard support on RAID set depending on RAID level.
* Enable/disable discard support on RAID set depending on
* RAID level and discard properties of underlying RAID members.
*/
static void configure_discard_support(struct dm_target *ti, struct raid_set *rs)
{
int i;
bool raid456;
/* Assume discards not supported until after checks below. */
ti->discards_supported = false;
/* RAID level 4,5,6 require discard_zeroes_data for data integrity! */
if (rs->md.level == 4 || rs->md.level == 5 || rs->md.level == 6)
return; /* discard_zeroes_data cannot be trusted as reliable */
raid456 = (rs->md.level == 4 || rs->md.level == 5 || rs->md.level == 6);
for (i = 0; i < rs->md.raid_disks; i++) {
struct request_queue *q = bdev_get_queue(rs->dev[i].rdev.bdev);
if (!q || !blk_queue_discard(q))
return;
if (raid456) {
if (!q->limits.discard_zeroes_data)
return;
if (!devices_handle_discard_safely) {
DMERR("raid456 discard support disabled due to discard_zeroes_data uncertainty.");
DMERR("Set dm-raid.devices_handle_discard_safely=Y to override.");
return;
}
}
}
/* All RAID members properly support discards */
ti->discards_supported = true;
/*
* RAID1 and RAID10 personalities require bio splitting,
* RAID0/4/5/6 don't and process large discard bios properly.
*/
ti->split_discard_bios = true;
ti->split_discard_bios = !!(rs->md.level == 1 || rs->md.level == 10);
ti->num_discard_bios = 1;
}
@ -1709,6 +1735,10 @@ static void __exit dm_raid_exit(void)
module_init(dm_raid_init);
module_exit(dm_raid_exit);
module_param(devices_handle_discard_safely, bool, 0644);
MODULE_PARM_DESC(devices_handle_discard_safely,
"Set to Y if all devices in each array reliably return zeroes on reads from discarded regions");
MODULE_DESCRIPTION(DM_NAME " raid4/5/6 target");
MODULE_ALIAS("dm-raid1");
MODULE_ALIAS("dm-raid10");