[PATCH v4 06/11] md/raid5-cache: Drop RCU usage of conf->log
From: Logan Gunthorpe <logang@deltatee.com>
Date: 2022-06-08 16:28:51
Also in:
lkml
Subsystem:
software raid (multiple disks) support, the rest · Maintainers:
Song Liu, Yu Kuai, Linus Torvalds
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 <logang@deltatee.com> Reviewed-by: Christoph Hellwig <hch@lst.de> --- 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 ca8fc317da95..b1fc65e113f8 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);
--
2.30.2