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md: Just use RCU when checking for overlap between arrays. 

We don't really need the full mddev_lock here, and having to
drop it is messy.
RCU is enough to protect these lists.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2014-09-29 15:33:20 +10:00
parent 50bd377405
commit 8b1afc3d67
1 changed files with 7 additions and 8 deletions
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15
drivers/md/md.c
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@ -2963,20 +2963,20 @@ rdev_size_store(struct md_rdev *rdev, const char *buf, size_t len)
rdev->sectors = sectors;
if (sectors > oldsectors && my_mddev->external) {
/* need to check that all other rdevs with the same ->bdev
* do not overlap. We need to unlock the mddev to avoid
* a deadlock. We have already changed rdev->sectors, and if
* we have to change it back, we will have the lock again.
/* Need to check that all other rdevs with the same
* ->bdev do not overlap. 'rcu' is sufficient to walk
* the rdev lists safely.
* This check does not provide a hard guarantee, it
* just helps avoid dangerous mistakes.
*/
struct mddev *mddev;
int overlap = 0;
struct list_head *tmp;
mddev_unlock(my_mddev);
rcu_read_lock();
for_each_mddev(mddev, tmp) {
struct md_rdev *rdev2;
mddev_lock_nointr(mddev);
rdev_for_each(rdev2, mddev)
if (rdev->bdev == rdev2->bdev &&
rdev != rdev2 &&
@ -2986,13 +2986,12 @@ rdev_size_store(struct md_rdev *rdev, const char *buf, size_t len)
overlap = 1;
break;
}
mddev_unlock(mddev);
if (overlap) {
mddev_put(mddev);
break;
}
}
mddev_lock_nointr(my_mddev);
rcu_read_unlock();
if (overlap) {
/* Someone else could have slipped in a size
* change here, but doing so is just silly.