In add_stripe_bio(), if the stripe_head is in batch list, the incoming
bio is regarded as overlapping, and the bit R5_Overlap on this stripe_head
is set. break_stripe_batch_list() checks bit R5_Overlap on each stripe_head
first then assigns NULL to sh->batch_head.
If break_stripe_batch_list() checks bit R5_Overlap on stripe_head A
after add_stripe_bio() finds stripe_head A is in batch list and before
add_stripe_bio() sets bit R5_Overlapt of stripe_head A,
break_stripe_batch_list() would not know there's a process in
wait_for_overlap and needs to call wake_up(). There's a huge chance a
process never returns from schedule() if add_stripe_bio() is called
from raid5_make_request().
In break_stripe_batch_list(), assigning NULL to sh->batch_head should
be done before it checks bit R5_Overlap of a stripe_head.
Signed-off-by: Amy Chiang <amychiang@xxxxxxxx>
---
drivers/md/raid5.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 928e24a..65f9af0 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4611,15 +4611,15 @@ static void break_stripe_batch_list(struct stripe_head *head_sh,
sh->check_state = head_sh->check_state;
sh->reconstruct_state = head_sh->reconstruct_state;
+ spin_lock_irq(&sh->stripe_lock);
+ sh->batch_head = NULL;
+ spin_unlock_irq(&sh->stripe_lock);
for (i = 0; i < sh->disks; i++) {
if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
do_wakeup = 1;
sh->dev[i].flags = head_sh->dev[i].flags &
(~((1 << R5_WriteError) | (1 << R5_Overlap)));
}
- spin_lock_irq(&sh->stripe_lock);
- sh->batch_head = NULL;
- spin_unlock_irq(&sh->stripe_lock);
if (handle_flags == 0 ||
sh->state & handle_flags)
set_bit(STRIPE_HANDLE, &sh->state);
--
2.7.4
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