block: remove rcu_read_lock() from part_stat_lock()
The RCU lock is required only in disk_map_sector_rcu() to lookup the
partition. After that request holds reference to related hd_struct.
Replace get_cpu() with preempt_disable() - returned cpu index is unused.
[hch: rebased]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/genhd.c b/block/genhd.c
index 3e7df0a..1a76593 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -321,11 +321,12 @@ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector)
struct hd_struct *part;
int i;
+ rcu_read_lock();
ptbl = rcu_dereference(disk->part_tbl);
part = rcu_dereference(ptbl->last_lookup);
if (part && sector_in_part(part, sector) && hd_struct_try_get(part))
- return part;
+ goto out_unlock;
for (i = 1; i < ptbl->len; i++) {
part = rcu_dereference(ptbl->part[i]);
@@ -339,10 +340,14 @@ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector)
if (!hd_struct_try_get(part))
break;
rcu_assign_pointer(ptbl->last_lookup, part);
- return part;
+ goto out_unlock;
}
}
- return &disk->part0;
+
+ part = &disk->part0;
+out_unlock:
+ rcu_read_unlock();
+ return part;
}
/**