md: stop using for_each_mddev in md_notify_reboot

Just do a simple list_for_each_entry_safe on all_mddevs, and only grab a
reference when we drop the lock.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index f7d5865..f5d4669 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -9585,11 +9585,13 @@ EXPORT_SYMBOL_GPL(rdev_clear_badblocks);
 static int md_notify_reboot(struct notifier_block *this,
                            unsigned long code, void *x)
 {
-       struct list_head *tmp;
-       struct mddev *mddev;
+       struct mddev *mddev, *n;
        int need_delay = 0;
 
-       for_each_mddev(mddev, tmp) {
+       spin_lock(&all_mddevs_lock);
+       list_for_each_entry_safe(mddev, n, &all_mddevs, all_mddevs) {
+               mddev_get(mddev);
+               spin_unlock(&all_mddevs_lock);
                if (mddev_trylock(mddev)) {
                        if (mddev->pers)
                                __md_stop_writes(mddev);
@@ -9598,7 +9600,11 @@ static int md_notify_reboot(struct notifier_block *this,
                        mddev_unlock(mddev);
                }
                need_delay = 1;
+               mddev_put(mddev);
+               spin_lock(&all_mddevs_lock);
        }
+       spin_unlock(&all_mddevs_lock);
+
        /*
         * certain more exotic SCSI devices are known to be
         * volatile wrt too early system reboots. While the