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[PATCH] md: Improve locking around error handling

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The error handling routines don't use proper locking, and so two concurrent
errors could trigger a problem.

So:
  - use test-and-set and test-and-clear to synchonise
    the In_sync bits with the ->degraded count
  - use the spinlock to protect updates to the
    degraded count (could use an atomic_t but that
    would be a bigger change in code, and isn't
    really justified)
  - remove un-necessary locking in raid5

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
NeilBrown
2006-10-03 01:15:53 -07:00
committed by Linus Torvalds
parent 11ce99e625
commit c04be0aa82
3 changed files with 31 additions and 17 deletions
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20
drivers/md/raid5.c
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@@ -636,7 +636,6 @@ static int raid5_end_write_request (struct bio *bi, unsigned int bytes_done,
struct stripe_head *sh = bi->bi_private;
raid5_conf_t *conf = sh->raid_conf;
int disks = sh->disks, i;
unsigned long flags;
int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
if (bi->bi_size)
@@ -654,7 +653,6 @@ static int raid5_end_write_request (struct bio *bi, unsigned int bytes_done,
return 0;
}
spin_lock_irqsave(&conf->device_lock, flags);
if (!uptodate)
md_error(conf->mddev, conf->disks[i].rdev);
@@ -662,8 +660,7 @@ static int raid5_end_write_request (struct bio *bi, unsigned int bytes_done,
clear_bit(R5_LOCKED, &sh->dev[i].flags);
set_bit(STRIPE_HANDLE, &sh->state);
__release_stripe(conf, sh);
spin_unlock_irqrestore(&conf->device_lock, flags);
release_stripe(sh);
return 0;
}
@@ -697,9 +694,11 @@ static void error(mddev_t *mddev, mdk_rdev_t *rdev)
if (!test_bit(Faulty, &rdev->flags)) {
set_bit(MD_CHANGE_DEVS, &mddev->flags);
if (test_bit(In_sync, &rdev->flags)) {
if (test_and_clear_bit(In_sync, &rdev->flags)) {
unsigned long flags;
spin_lock_irqsave(&conf->device_lock, flags);
mddev->degraded++;
clear_bit(In_sync, &rdev->flags);
spin_unlock_irqrestore(&conf->device_lock, flags);
/*
* if recovery was running, make sure it aborts.
*/
@@ -3418,9 +3417,11 @@ static int raid5_spare_active(mddev_t *mddev)
tmp = conf->disks + i;
if (tmp->rdev
&& !test_bit(Faulty, &tmp->rdev->flags)
&& !test_bit(In_sync, &tmp->rdev->flags)) {
&& !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
unsigned long flags;
spin_lock_irqsave(&conf->device_lock, flags);
mddev->degraded--;
set_bit(In_sync, &tmp->rdev->flags);
spin_unlock_irqrestore(&conf->device_lock, flags);
}
}
print_raid5_conf(conf);
@@ -3556,6 +3557,7 @@ static int raid5_start_reshape(mddev_t *mddev)
struct list_head *rtmp;
int spares = 0;
int added_devices = 0;
unsigned long flags;
if (mddev->degraded ||
test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
@@ -3597,7 +3599,9 @@ static int raid5_start_reshape(mddev_t *mddev)
break;
}
spin_lock_irqsave(&conf->device_lock, flags);
mddev->degraded = (conf->raid_disks - conf->previous_raid_disks) - added_devices;
spin_unlock_irqrestore(&conf->device_lock, flags);
mddev->raid_disks = conf->raid_disks;
mddev->reshape_position = 0;
set_bit(MD_CHANGE_DEVS, &mddev->flags);