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authorNeilBrown <neilb@suse.com>2016-06-02 16:19:53 +1000
committerShaohua Li <shli@fb.com>2016-06-13 11:54:22 -0700
commitd787be4092e27728cb4c012bee9762098ef3c662 (patch)
treeb8de57ed842d3c01f6fdd4f6ee5be6408763a993
parentf5b67ae86ee317db20c0e10d54f16a0bbbd3207d (diff)
downloadop-kernel-dev-d787be4092e27728cb4c012bee9762098ef3c662.zip
op-kernel-dev-d787be4092e27728cb4c012bee9762098ef3c662.tar.gz
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 <neilb@suse.com> Signed-off-by: Shaohua Li <shli@fb.com>
-rw-r--r--drivers/md/md.c29
-rw-r--r--drivers/md/md.h5
-rw-r--r--drivers/md/multipath.c14
-rw-r--r--drivers/md/raid1.c17
-rw-r--r--drivers/md/raid10.c19
-rw-r--r--drivers/md/raid5.c15
6 files changed, 69 insertions, 30 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 0793754..2ed547f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8180,15 +8180,34 @@ static int remove_and_add_spares(struct mddev *mddev,
struct md_rdev *rdev;
int spares = 0;
int removed = 0;
+ bool remove_some = false;
- rdev_for_each(rdev, mddev)
+ rdev_for_each(rdev, mddev) {
+ if ((this == NULL || rdev == this) &&
+ rdev->raid_disk >= 0 &&
+ !test_bit(Blocked, &rdev->flags) &&
+ test_bit(Faulty, &rdev->flags) &&
+ atomic_read(&rdev->nr_pending)==0) {
+ /* Faulty non-Blocked devices with nr_pending == 0
+ * never get nr_pending incremented,
+ * never get Faulty cleared, and never get Blocked set.
+ * So we can synchronize_rcu now rather than once per device
+ */
+ remove_some = true;
+ set_bit(RemoveSynchronized, &rdev->flags);
+ }
+ }
+
+ if (remove_some)
+ synchronize_rcu();
+ rdev_for_each(rdev, mddev) {
if ((this == NULL || rdev == this) &&
rdev->raid_disk >= 0 &&
!test_bit(Blocked, &rdev->flags) &&
- (test_bit(Faulty, &rdev->flags) ||
+ ((test_bit(RemoveSynchronized, &rdev->flags) ||
(!test_bit(In_sync, &rdev->flags) &&
!test_bit(Journal, &rdev->flags))) &&
- atomic_read(&rdev->nr_pending)==0) {
+ atomic_read(&rdev->nr_pending)==0)) {
if (mddev->pers->hot_remove_disk(
mddev, rdev) == 0) {
sysfs_unlink_rdev(mddev, rdev);
@@ -8196,6 +8215,10 @@ static int remove_and_add_spares(struct mddev *mddev,
removed++;
}
}
+ if (remove_some && test_bit(RemoveSynchronized, &rdev->flags))
+ clear_bit(RemoveSynchronized, &rdev->flags);
+ }
+
if (removed && mddev->kobj.sd)
sysfs_notify(&mddev->kobj, NULL, "degraded");
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 03b19aa..dc65ca6 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -163,6 +163,11 @@ enum flag_bits {
* than other devices in the array
*/
ClusterRemove,
+ RemoveSynchronized, /* synchronize_rcu() was called after
+ * this device was known to be faulty,
+ * so it is safe to remove without
+ * another synchronize_rcu() call.
+ */
};
static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 7eb9972..c145a5a 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -298,12 +298,14 @@ static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
goto abort;
}
p->rdev = NULL;
- synchronize_rcu();
- if (atomic_read(&rdev->nr_pending)) {
- /* lost the race, try later */
- err = -EBUSY;
- p->rdev = rdev;
- goto abort;
+ if (!test_bit(RemoveSynchronized, &rdev->flags)) {
+ synchronize_rcu();
+ if (atomic_read(&rdev->nr_pending)) {
+ /* lost the race, try later */
+ err = -EBUSY;
+ p->rdev = rdev;
+ goto abort;
+ }
}
err = md_integrity_register(mddev);
}
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 34f20c0..5027ef4 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1656,13 +1656,16 @@ static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
goto abort;
}
p->rdev = NULL;
- synchronize_rcu();
- if (atomic_read(&rdev->nr_pending)) {
- /* lost the race, try later */
- err = -EBUSY;
- p->rdev = rdev;
- goto abort;
- } else if (conf->mirrors[conf->raid_disks + number].rdev) {
+ if (!test_bit(RemoveSynchronized, &rdev->flags)) {
+ synchronize_rcu();
+ if (atomic_read(&rdev->nr_pending)) {
+ /* lost the race, try later */
+ err = -EBUSY;
+ p->rdev = rdev;
+ goto abort;
+ }
+ }
+ if (conf->mirrors[conf->raid_disks + number].rdev) {
/* We just removed a device that is being replaced.
* Move down the replacement. We drain all IO before
* doing this to avoid confusion.
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 34facda..8ee5d96 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);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index f6a191a..413cc7d 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7197,12 +7197,15 @@ static int raid5_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;
- } 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;
+ }
+ }
+ if (p->replacement) {
/* We must have just cleared 'rdev' */
p->rdev = p->replacement;
clear_bit(Replacement, &p->replacement->flags);
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