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authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>2020-05-27 08:24:17 +0300
committerJens Axboe <axboe@kernel.dk>2020-05-27 14:21:23 +0300
commit8ab1d40a646e753adb6814642432a093d93dbf47 (patch)
treef70e9ee9cc1ea5823cba3865f380a597ef5db3ca
parentb5af37ab3a2b143e278340d2c6fa5790d53817e7 (diff)
downloadlinux-8ab1d40a646e753adb6814642432a093d93dbf47.tar.xz
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>
-rw-r--r--block/genhd.c11
-rw-r--r--include/linux/part_stat.h4
2 files changed, 10 insertions, 5 deletions
diff --git a/block/genhd.c b/block/genhd.c
index 3e7df0a3e6bb..1a7659327664 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;
}
/**
diff --git a/include/linux/part_stat.h b/include/linux/part_stat.h
index 6644197980b9..a6b0938ce82e 100644
--- a/include/linux/part_stat.h
+++ b/include/linux/part_stat.h
@@ -21,8 +21,8 @@ struct disk_stats {
*
* part_stat_read() can be called at any time.
*/
-#define part_stat_lock() ({ rcu_read_lock(); get_cpu(); })
-#define part_stat_unlock() do { put_cpu(); rcu_read_unlock(); } while (0)
+#define part_stat_lock() preempt_disable()
+#define part_stat_unlock() preempt_enable()
#define part_stat_get_cpu(part, field, cpu) \
(per_cpu_ptr((part)->dkstats, (cpu))->field)