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md/raid5: ensure sync and DISCARD don't happen at the same time. 

A number of problems can occur due to races between
resync/recovery and discard.

- if sync_request calls handle_stripe() while a discard is
  happening on the stripe, it might call handle_stripe_clean_event
  before all of the individual discard requests have completed
  (so some devices are still locked, but not all).
  Since commit ca64cae960
     md/raid5: Make sure we clear R5_Discard when discard is finished.
  this will cause R5_Discard to be cleared for the parity device,
  so handle_stripe_clean_event() will not be called when the other
  devices do become unlocked, so their ->written will not be cleared.
  This ultimately leads to a WARN_ON in init_stripe and a lock-up.

- If handle_stripe_clean_event() does clear R5_UPTODATE at an awkward
  time for resync, it can lead to s->uptodate being less than disks
  in handle_parity_checks5(), which triggers a BUG (because it is
  one).

So:
 - keep R5_Discard on the parity device until all other devices have
   completed their discard request
 - make sure we don't try to have a 'discard' and a 'sync' action at
   the same time.
   This involves a new stripe flag to we know when a 'discard' is
   happening, and the use of R5_Overlap on the parity disk so when a
   discard is wanted while a sync is active, so we know to wake up
   the discard at the appropriate time.

Discard support for RAID5 was added in 3.7, so this is suitable for
any -stable kernel since 3.7.

Cc: stable@vger.kernel.org (v3.7+)
Reported-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Tested-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2013-03-12 12:18:06 +11:00
parent 90584fc93d
commit f8dfcffd04
2 changed files with 40 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
drivers/md/raid5.c
View File

@ -2576,6 +2576,8 @@ handle_failed_sync(struct r5conf *conf, struct stripe_head *sh,
int i;
clear_bit(STRIPE_SYNCING, &sh->state);
if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
wake_up(&conf->wait_for_overlap);
s->syncing = 0;
s->replacing = 0;
/* There is nothing more to do for sync/check/repair.
@ -2749,6 +2751,7 @@ static void handle_stripe_clean_event(struct r5conf *conf,
{
int i;
struct r5dev *dev;
int discard_pending = 0;
for (i = disks; i--; )
if (sh->dev[i].written) {
@ -2777,9 +2780,23 @@ static void handle_stripe_clean_event(struct r5conf *conf,
STRIPE_SECTORS,
!test_bit(STRIPE_DEGRADED, &sh->state),
0);
}
} else if (test_bit(R5_Discard, &sh->dev[i].flags))
clear_bit(R5_Discard, &sh->dev[i].flags);
} else if (test_bit(R5_Discard, &dev->flags))
discard_pending = 1;
}
if (!discard_pending &&
test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags)) {
clear_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
if (sh->qd_idx >= 0) {
clear_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
clear_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags);
}
/* now that discard is done we can proceed with any sync */
clear_bit(STRIPE_DISCARD, &sh->state);
if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state))
set_bit(STRIPE_HANDLE, &sh->state);
}
if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
if (atomic_dec_and_test(&conf->pending_full_writes))
@ -3431,9 +3448,15 @@ static void handle_stripe(struct stripe_head *sh)
return;
}
if (test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
set_bit(STRIPE_SYNCING, &sh->state);
clear_bit(STRIPE_INSYNC, &sh->state);
if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
spin_lock(&sh->stripe_lock);
/* Cannot process 'sync' concurrently with 'discard' */
if (!test_bit(STRIPE_DISCARD, &sh->state) &&
test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
set_bit(STRIPE_SYNCING, &sh->state);
clear_bit(STRIPE_INSYNC, &sh->state);
}
spin_unlock(&sh->stripe_lock);
}
clear_bit(STRIPE_DELAYED, &sh->state);
@ -3593,6 +3616,8 @@ static void handle_stripe(struct stripe_head *sh)
test_bit(STRIPE_INSYNC, &sh->state)) {
md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
clear_bit(STRIPE_SYNCING, &sh->state);
if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
wake_up(&conf->wait_for_overlap);
}
/* If the failed drives are just a ReadError, then we might need
@ -4159,6 +4184,13 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
sh = get_active_stripe(conf, logical_sector, 0, 0, 0);
prepare_to_wait(&conf->wait_for_overlap, &w,
TASK_UNINTERRUPTIBLE);
set_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags);
if (test_bit(STRIPE_SYNCING, &sh->state)) {
release_stripe(sh);
schedule();
goto again;
}
clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags);
spin_lock_irq(&sh->stripe_lock);
for (d = 0; d < conf->raid_disks; d++) {
if (d == sh->pd_idx || d == sh->qd_idx)
@ -4171,6 +4203,7 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
goto again;
}
}
set_bit(STRIPE_DISCARD, &sh->state);
finish_wait(&conf->wait_for_overlap, &w);
for (d = 0; d < conf->raid_disks; d++) {
if (d == sh->pd_idx || d == sh->qd_idx)

1
drivers/md/raid5.h
View File

@ -323,6 +323,7 @@ enum {
STRIPE_COMPUTE_RUN,
STRIPE_OPS_REQ_PENDING,
STRIPE_ON_UNPLUG_LIST,
STRIPE_DISCARD,
};
/*