From: Yu Kuai yukuai3@huawei.com
mainline inclusion from mainline-next-20231220 commit 7ecab28c3b2c26c1a51154d997433e8432eb49ba category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8T02O
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Because it's safe to accees rdev from conf: - If any spinlock is held, because synchronize_rcu() from md_kick_rdev_from_array() will prevent 'rdev' to be freed until spinlock is released; - If there is normal IO inflight, because mddev_suspend() will prevent rdev to be added or removed from array;
And these will cover all the scenarios in md-multipath.
Signed-off-by: Yu Kuai yukuai3@huawei.com Signed-off-by: Song Liu song@kernel.org Link: https://lore.kernel.org/r/20231125081604.3939938-6-yukuai1@huaweicloud.com Signed-off-by: Li Nan linan122@huawei.com --- drivers/md/md-multipath.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/drivers/md/md-multipath.c b/drivers/md/md-multipath.c index aa77133f3188..19c8625ea642 100644 --- a/drivers/md/md-multipath.c +++ b/drivers/md/md-multipath.c @@ -32,17 +32,15 @@ static int multipath_map (struct mpconf *conf) * now we use the first available disk. */
- rcu_read_lock(); for (i = 0; i < disks; i++) { - struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev); + struct md_rdev *rdev = conf->multipaths[i].rdev; + if (rdev && test_bit(In_sync, &rdev->flags) && !test_bit(Faulty, &rdev->flags)) { atomic_inc(&rdev->nr_pending); - rcu_read_unlock(); return i; } } - rcu_read_unlock();
pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n"); return (-1); @@ -137,14 +135,16 @@ static void multipath_status(struct seq_file *seq, struct mddev *mddev) struct mpconf *conf = mddev->private; int i;
+ lockdep_assert_held(&mddev->lock); + seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->raid_disks - mddev->degraded); - rcu_read_lock(); for (i = 0; i < conf->raid_disks; i++) { - struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev); - seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_"); + struct md_rdev *rdev = READ_ONCE(conf->multipaths[i].rdev); + + seq_printf(seq, "%s", + rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_"); } - rcu_read_unlock(); seq_putc(seq, ']'); }
@@ -182,7 +182,7 @@ static void multipath_error (struct mddev *mddev, struct md_rdev *rdev) conf->raid_disks - mddev->degraded); }
-static void print_multipath_conf (struct mpconf *conf) +static void print_multipath_conf(struct mpconf *conf) { int i; struct multipath_info *tmp; @@ -195,6 +195,7 @@ static void print_multipath_conf (struct mpconf *conf) pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded, conf->raid_disks);
+ lockdep_assert_held(&conf->mddev->reconfig_mutex); for (i = 0; i < conf->raid_disks; i++) { tmp = conf->multipaths + i; if (tmp->rdev) @@ -231,7 +232,7 @@ static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev) rdev->raid_disk = path; set_bit(In_sync, &rdev->flags); spin_unlock_irq(&conf->device_lock); - rcu_assign_pointer(p->rdev, rdev); + WRITE_ONCE(p->rdev, rdev); err = 0; break; } @@ -257,7 +258,7 @@ static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev) err = -EBUSY; goto abort; } - p->rdev = NULL; + WRITE_ONCE(p->rdev, NULL); err = md_integrity_register(mddev); } abort: