Commit 7769085c authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Jens Axboe
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md/raid5-cache: Drop RCU usage of conf->log 



The only place that uses RCU to access conf->log is in
r5l_log_disk_error(). This function is mostly used in the IO path
and once with mddev_lock() held in raid5_change_consistency_policy().

It is known that the IO will be suspended before the log is freed and
r5l_log_exit() is called with the mddev_lock() held.

This should mean that conf->log can not be freed while the function is
being called, so the RCU protection is not necessary. Drop the
rcu_read_lock() as well as the synchronize_rcu() and
rcu_assign_pointer() usage.

Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 78ede6a0

drivers/md/raid5-cache.c

+5 −11
Original line number Diff line number Diff line
@@ -1590,18 +1590,13 @@ void r5l_quiesce(struct r5l_log *log, int quiesce) 


bool r5l_log_disk_error(struct r5conf *conf)

{

	struct r5l_log *log;

	bool ret;

	/* don't allow write if journal disk is missing */

	rcu_read_lock();

	log = rcu_dereference(conf->log);

	struct r5l_log *log = conf->log;



	/* don't allow write if journal disk is missing */

	if (!log)

		ret = test_bit(MD_HAS_JOURNAL, &conf->mddev->flags);

		return test_bit(MD_HAS_JOURNAL, &conf->mddev->flags);

	else

		ret = test_bit(Faulty, &log->rdev->flags);

	rcu_read_unlock();

	return ret;

		return test_bit(Faulty, &log->rdev->flags);

}



#define R5L_RECOVERY_PAGE_POOL_SIZE 256
@@ -3148,7 +3143,7 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev) 
	spin_lock_init(&log->stripe_in_journal_lock);

	atomic_set(&log->stripe_in_journal_count, 0);



	rcu_assign_pointer(conf->log, log);

	conf->log = log;



	set_bit(MD_HAS_JOURNAL, &conf->mddev->flags);

	return 0;
@@ -3171,7 +3166,6 @@ void r5l_exit_log(struct r5conf *conf) 
	struct r5l_log *log = conf->log;



	conf->log = NULL;

	synchronize_rcu();



	/* Ensure disable_writeback_work wakes up and exits */

	wake_up(&conf->mddev->sb_wait);