[ 76/98] md/raid5: schedule_construction should abort if nothing to do.

Greg Kroah-Hartman
2013-03-26T23:32:25Z

From: NeilBrown <neilb@suse.de>

commit ce7d363aaf1e28be8406a2976220944ca487e8ca upstream.

Since commit 1ed850f356a0a422013846b5291acff08815008b
md/raid5: make sure to_read and to_write never go negative.

It has been possible for handle_stripe_dirtying to be called
when there isn't actually any work to do.
It then calls schedule_reconstruction() which will set R5_LOCKED
on the parity block(s) even when nothing else is happening.
This then causes problems in do_release_stripe().

So add checks to schedule_reconstruction() so that if it doesn't
find anything to do, it just aborts.

This bug was introduced in v3.7, so the patch is suitable
for -stable kernels since then.

Reported-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/raid5.c | 38 ++++++++++++++++++++++----------------
1 file changed, 22 insertions(+), 16 deletions(-)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2319,17 +2319,6 @@ schedule_reconstruction(struct stripe_he
int level = conf->level;

if (rcw) {
- /* if we are not expanding this is a proper write request, and
- * there will be bios with new data to be drained into the
- * stripe cache
- */
- if (!expand) {
- sh->reconstruct_state = reconstruct_state_drain_run;
- set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
- } else
- sh->reconstruct_state = reconstruct_state_run;
-
- set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);

for (i = disks; i--; ) {
struct r5dev *dev = &sh->dev[i];
@@ -2342,6 +2331,21 @@ schedule_reconstruction(struct stripe_he
s->locked++;
}
}
+ /* if we are not expanding this is a proper write request, and
+ * there will be bios with new data to be drained into the
+ * stripe cache
+ */
+ if (!expand) {
+ if (!s->locked)
+ /* False alarm, nothing to do */
+ return;
+ sh->reconstruct_state = reconstruct_state_drain_run;
+ set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
+ } else
+ sh->reconstruct_state = reconstruct_state_run;
+
+ set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
+
if (s->locked + conf->max_degraded == disks)
if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
atomic_inc(&conf->pending_full_writes);
@@ -2350,11 +2354,6 @@ schedule_reconstruction(struct stripe_he
BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));

- sh->reconstruct_state = reconstruct_state_prexor_drain_run;
- set_bit(STRIPE_OP_PREXOR, &s->ops_request);
- set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
- set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
-
for (i = disks; i--; ) {
struct r5dev *dev = &sh->dev[i];
if (i == pd_idx)
@@ -2369,6 +2368,13 @@ schedule_reconstruction(struct stripe_he
s->locked++;
}
}
+ if (!s->locked)
+ /* False alarm - nothing to do */
+ return;
+ sh->reconstruct_state = reconstruct_state_prexor_drain_run;
+ set_bit(STRIPE_OP_PREXOR, &s->ops_request);
+ set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
+ set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
}

/* keep the parity disk(s) locked while asynchronous operations