From 76fd9cf0770e32f7e14f929bfb1eac43428515c8 Mon Sep 17 00:00:00 2001 From: Logan Gunthorpe Date: Wed, 8 Jun 2022 10:27:51 -0600 Subject: [PATCH] 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: Logan Gunthorpe Reviewed-by: Christoph Hellwig Signed-off-by: Song Liu Signed-off-by: Jens Axboe --- drivers/md/raid5-cache.c | 16 +++++----------- 1 file changed, 5 insertions(+), 11 deletions(-) diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c index 4da88888fbfc2..d9b94e25e815f 100644 --- a/drivers/md/raid5-cache.c +++ b/drivers/md/raid5-cache.c @@ -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); -- 2.39.5