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-   -   DM RAID: Set recovery flags on resume (http://www.linux-archive.org/device-mapper-development/657089-dm-raid-set-recovery-flags-resume.html)

Jonathan Brassow 04-18-2012 02:36 AM

DM RAID: Set recovery flags on resume
 
Properly initialize MD recovery flags when resuming device-mapper devices.

When a device-mapper device is suspended, all I/O must stop. This is done by
calling 'md_stop_writes' and 'mddev_suspend'. These calls in-turn manipulate
the recovery flags - including setting 'MD_RECOVERY_FROZEN'. The DM device
may have been suspended while recovery was not yet complete, so the process
needs to pick-up where it left off. Since 'mddev_resume' does not unset
'MD_RECOVERY_FROZEN' and set 'MD_RECOVERY_NEEDED', we must do it ourselves.
'MD_RECOVERY_NEEDED' can safely be set in 'mddev_resume', but 'MD_RECOVERY_FROZEN'
must be set outside of 'mddev_resume' due to how MD handles RAID reshaping.
(e.g. It is possible for a user to delay reshaping a RAID5->RAID6 by purposefully
setting 'MD_RECOVERY_FROZEN'. Clearing it in 'mddev_resume' would override the
desired behavior.)

Because 'mddev_resume' already unconditionally calls 'md_wakeup_thread(mddev->thread)'
there is no need to make this call from 'raid_resume' since it calls 'mddev_resume'.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>

Index: linux-upstream/drivers/md/dm-raid.c
================================================== =================
--- linux-upstream.orig/drivers/md/dm-raid.c
+++ linux-upstream/drivers/md/dm-raid.c
@@ -1255,9 +1255,9 @@ static void raid_resume(struct dm_target
if (!rs->bitmap_loaded) {
bitmap_load(&rs->md);
rs->bitmap_loaded = 1;
- } else
- md_wakeup_thread(rs->md.thread);
+ }

+ clear_bit(MD_RECOVERY_FROZEN, &rs->md.recovery);
mddev_resume(&rs->md);
}

Index: linux-upstream/drivers/md/md.c
================================================== =================
--- linux-upstream.orig/drivers/md/md.c
+++ linux-upstream/drivers/md/md.c
@@ -400,6 +400,7 @@ void mddev_resume(struct mddev *mddev)
wake_up(&mddev->sb_wait);
mddev->pers->quiesce(mddev, 0);

+ set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
md_wakeup_thread(mddev->thread);
md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
}


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