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