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>
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 @@
* 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,