md: reduce the number of synchronize_rcu() calls when multiple devices fail.

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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>

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This commit is contained in:

NeilBrown 2016-06-02 16:19:53 +10:00 • committed by Shaohua Li

parent f5b67ae86e

commit d787be4092

6 changed files with 69 additions and 30 deletions

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29

drivers/md/md.c

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5

drivers/md/md.h

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14

drivers/md/multipath.c

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17

drivers/md/raid1.c

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19

drivers/md/raid10.c

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15

drivers/md/raid5.c

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