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Date: Thu, 16 Jul 2015 11:16:45 +0800
From: Ming Lei <tom.leiming@...il.com>
To: Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Cc: Mike Snitzer <snitzer@...hat.com>, Tejun Heo <tj@...nel.org>,
Ming Lei <tom.leiming@...il.com>
Subject: [PATCH 2/4] block: partition: convert percpu ref
Percpu refcount is the perfect match for partition's case,
and the conversion is quite straight.
With the convertion, one pair of atomic inc/dec can be saved
for accounting block I/O, which is run in hot path of block I/O.
Signed-off-by: Ming Lei <tom.leiming@...il.com>
---
block/genhd.c | 6 +++++-
block/partition-generic.c | 9 +++++----
include/linux/genhd.h | 27 +++++++++++++++++----------
3 files changed, 27 insertions(+), 15 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index ed3f5b9..3213b66 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1284,7 +1284,11 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
* converted to make use of bd_mutex and sequence counters.
*/
seqcount_init(&disk->part0.nr_sects_seq);
- hd_ref_init(&disk->part0);
+ if (hd_ref_init(&disk->part0)) {
+ hd_free_part(&disk->part0);
+ kfree(disk);
+ return NULL;
+ }
disk->minors = minors;
rand_initialize_disk(disk);
diff --git a/block/partition-generic.c b/block/partition-generic.c
index eca0d02..e771113 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -232,8 +232,9 @@ static void delete_partition_rcu_cb(struct rcu_head *head)
put_device(part_to_dev(part));
}
-void __delete_partition(struct hd_struct *part)
+void __delete_partition(struct percpu_ref *ref)
{
+ struct hd_struct *part = container_of(ref, struct hd_struct, ref);
call_rcu(&part->rcu_head, delete_partition_rcu_cb);
}
@@ -254,7 +255,7 @@ void delete_partition(struct gendisk *disk, int partno)
kobject_put(part->holder_dir);
device_del(part_to_dev(part));
- hd_struct_put(part);
+ hd_struct_kill(part);
}
static ssize_t whole_disk_show(struct device *dev,
@@ -355,8 +356,8 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
if (!dev_get_uevent_suppress(ddev))
kobject_uevent(&pdev->kobj, KOBJ_ADD);
- hd_ref_init(p);
- return p;
+ if (!hd_ref_init(p))
+ return p;
out_free_info:
free_part_info(p);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index a221220..2adbfa6 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -13,6 +13,7 @@
#include <linux/kdev_t.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
+#include <linux/percpu-refcount.h>
#ifdef CONFIG_BLOCK
@@ -124,7 +125,7 @@ struct hd_struct {
#else
struct disk_stats dkstats;
#endif
- atomic_t ref;
+ struct percpu_ref ref;
struct rcu_head rcu_head;
};
@@ -611,7 +612,7 @@ extern struct hd_struct * __must_check add_partition(struct gendisk *disk,
sector_t len, int flags,
struct partition_meta_info
*info);
-extern void __delete_partition(struct hd_struct *);
+extern void __delete_partition(struct percpu_ref *);
extern void delete_partition(struct gendisk *, int);
extern void printk_all_partitions(void);
@@ -640,33 +641,39 @@ extern ssize_t part_fail_store(struct device *dev,
const char *buf, size_t count);
#endif /* CONFIG_FAIL_MAKE_REQUEST */
-static inline void hd_ref_init(struct hd_struct *part)
+static inline int hd_ref_init(struct hd_struct *part)
{
- atomic_set(&part->ref, 1);
- smp_mb();
+ if (percpu_ref_init(&part->ref, __delete_partition, 0,
+ GFP_KERNEL))
+ return -ENOMEM;
+ return 0;
}
static inline void hd_struct_get(struct hd_struct *part)
{
- atomic_inc(&part->ref);
- smp_mb__after_atomic();
+ percpu_ref_get(&part->ref);
}
static inline int hd_struct_try_get(struct hd_struct *part)
{
- return atomic_inc_not_zero(&part->ref);
+ return percpu_ref_tryget_live(&part->ref);
}
static inline void hd_struct_put(struct hd_struct *part)
{
- if (atomic_dec_and_test(&part->ref))
- __delete_partition(part);
+ percpu_ref_put(&part->ref);
+}
+
+static inline void hd_struct_kill(struct hd_struct *part)
+{
+ percpu_ref_kill(&part->ref);
}
static inline void hd_free_part(struct hd_struct *part)
{
free_part_stats(part);
free_part_info(part);
+ percpu_ref_exit(&part->ref);
}
/*
--
1.9.1
--
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