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md/raid5: remove rcu protection to access rdev from conf

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Because it's safe to accees rdev from conf:
 - If any spinlock is held, because synchronize_rcu() from
   md_kick_rdev_from_array() will prevent 'rdev' to be freed until
   spinlock is released;
 - If 'reconfig_lock' is held, because rdev can't be added or removed from
   array;
 - If there is normal IO inflight, because mddev_suspend() will prevent
   rdev to be added or removed from array;
 - If there is sync IO inflight, because 'MD_RECOVERY_RUNNING' is
   checked in remove_and_add_spares().

And these will cover all the scenarios in raid456.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231125081604.3939938-5-yukuai1@huaweicloud.com
This commit is contained in:
Yu Kuai
2023-11-25 16:16:03 +08:00
committed by Song Liu
parent 2d32777d60
commit ad8606702f
4 changed files with 69 additions and 144 deletions
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11
drivers/md/raid5-cache.c
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@@ -1890,28 +1890,22 @@ r5l_recovery_replay_one_stripe(struct r5conf *conf,
continue;
/* in case device is broken */
rcu_read_lock();
rdev = rcu_dereference(conf->disks[disk_index].rdev);
rdev = conf->disks[disk_index].rdev;
if (rdev) {
atomic_inc(&rdev->nr_pending);
rcu_read_unlock();
sync_page_io(rdev, sh->sector, PAGE_SIZE,
sh->dev[disk_index].page, REQ_OP_WRITE,
false);
rdev_dec_pending(rdev, rdev->mddev);
rcu_read_lock();
}
rrdev = rcu_dereference(conf->disks[disk_index].replacement);
rrdev = conf->disks[disk_index].replacement;
if (rrdev) {
atomic_inc(&rrdev->nr_pending);
rcu_read_unlock();
sync_page_io(rrdev, sh->sector, PAGE_SIZE,
sh->dev[disk_index].page, REQ_OP_WRITE,
false);
rdev_dec_pending(rrdev, rrdev->mddev);
rcu_read_lock();
}
rcu_read_unlock();
}
ctx->data_parity_stripes++;
out:
@@ -2948,7 +2942,6 @@ bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect)
if (!log)
return false;
WARN_ON_ONCE(!rcu_read_lock_held());
tree_index = r5c_tree_index(conf, sect);
slot = radix_tree_lookup(&log->big_stripe_tree, tree_index);
return slot != NULL;