From d787be4092e27728cb4c012bee9762098ef3c662 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 2 Jun 2016 16:19:53 +1000 Subject: md: reduce the number of synchronize_rcu() calls when multiple devices fail. Every time a device is removed with ->hot_remove_disk() a synchronize_rcu() call is made which can delay several milliseconds in some case. If lots of devices fail at once - as could happen with a large RAID10 where one set of devices are removed all at once - these delays can add up to be very inconcenient. As failure is not reversible we can check for that first, setting a separate flag if it is found, and then all synchronize_rcu() once for all the flagged devices. Then ->hot_remove_disk() function can skip the synchronize_rcu() step if the flag is set. fix build error(Shaohua) Signed-off-by: NeilBrown Signed-off-by: Shaohua Li --- drivers/md/raid10.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) (limited to 'drivers/md/raid10.c') diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 34facda18e72..8ee5d96e6a2d 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -1766,7 +1766,7 @@ static int raid10_remove_disk(struct mddev *mddev, struct md_rdev *rdev) err = -EBUSY; goto abort; } - /* Only remove faulty devices if recovery + /* Only remove non-faulty devices if recovery * is not possible. */ if (!test_bit(Faulty, &rdev->flags) && @@ -1778,13 +1778,16 @@ static int raid10_remove_disk(struct mddev *mddev, struct md_rdev *rdev) goto abort; } *rdevp = NULL; - synchronize_rcu(); - if (atomic_read(&rdev->nr_pending)) { - /* lost the race, try later */ - err = -EBUSY; - *rdevp = rdev; - goto abort; - } else if (p->replacement) { + if (!test_bit(RemoveSynchronized, &rdev->flags)) { + synchronize_rcu(); + if (atomic_read(&rdev->nr_pending)) { + /* lost the race, try later */ + err = -EBUSY; + *rdevp = rdev; + goto abort; + } + } + if (p->replacement) { /* We must have just cleared 'rdev' */ p->rdev = p->replacement; clear_bit(Replacement, &p->replacement->flags); -- cgit v1.2.3