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raid5: Use sequence counter with associated spinlock 

A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Song Liu <song@kernel.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-20-a.darwish@linutronix.de
This commit is contained in:
Ahmed S. Darwish 2020-07-20 17:55:25 +02:00 committed by Peter Zijlstra
parent 2647537197
commit 0a87b25ff2
2 changed files with 2 additions and 2 deletions
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2
drivers/md/raid5.c
View File

@ -6935,7 +6935,7 @@ static struct r5conf *setup_conf(struct mddev *mddev)
} else
goto abort;
spin_lock_init(&conf->device_lock);
seqcount_init(&conf->gen_lock);
seqcount_spinlock_init(&conf->gen_lock, &conf->device_lock);
mutex_init(&conf->cache_size_mutex);
init_waitqueue_head(&conf->wait_for_quiescent);
init_waitqueue_head(&conf->wait_for_stripe);

2
drivers/md/raid5.h
View File

@ -589,7 +589,7 @@ struct r5conf {
int prev_chunk_sectors;
int prev_algo;
short generation; /* increments with every reshape */
seqcount_t gen_lock; /* lock against generation changes */
seqcount_spinlock_t gen_lock; /* lock against generation changes */
unsigned long reshape_checkpoint; /* Time we last updated
* metadata */
long long min_offset_diff; /* minimum difference between