block: fix kabi broken in struct hd_struct

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I57S8D
CVE: NA

--------------------------------

Use reserved fields to fix kabi broken for field 'stat_time'. However,
for the field 'bd_stat_lock', spinlock_t can be up to 64 bytes, thus
reserved fields is not enough. And struct 'hd_struct' is internal of
other sutrct, thus declare a wrapper is infeasible. In order to fix
kabi broken for 'bd_stat_lock', use 'dev->mutex' instead.
Signed-off-by: NYu Kuai <yukuai3@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

block/genhd.c

@@ -1312,10 +1312,10 @@ static void part_get_stat_info(struct hd_struct *hd, struct disk_stats *stat,
 
 	if (queue_is_mq(q)) {
 		part_stat_lock();
-		spin_lock(&hd->bd_stat_lock);
+		mutex_lock(&part_to_dev(hd)->mutex);
 		part_set_stat_time(hd);
 		*inflight = blk_mq_in_flight_with_stat(q, hd);
-		spin_unlock(&hd->bd_stat_lock);
+		mutex_unlock(&part_to_dev(hd)->mutex);
 		part_stat_unlock();
 	} else {
 		*inflight = part_in_flight(hd);

block/partitions/core.c

@@ -416,7 +416,6 @@ static struct hd_struct *add_partition(struct gendisk *disk, int partno,
 	p->partno = partno;
 	p->read_only = get_disk_ro(disk) | test_bit(partno, disk->user_ro_bitmap);
 	p->stat_time = 0;
-	spin_lock_init(&p->bd_stat_lock);
 
 	if (info) {
 		struct partition_meta_info *pinfo;

include/linux/genhd.h

@@ -63,8 +63,6 @@ struct hd_struct {
 	seqcount_t nr_sects_seq;
 #endif
 	unsigned long stamp;
-	spinlock_t bd_stat_lock;
-	u64 stat_time;
 	struct disk_stats __percpu *dkstats;
 	struct percpu_ref ref;
 
@@ -78,7 +76,7 @@ struct hd_struct {
 #endif
 	struct rcu_work rcu_work;
 
-	KABI_RESERVE(1)
+	KABI_USE(1, u64 stat_time)
 	KABI_RESERVE(2)
 	KABI_RESERVE(3)
 	KABI_RESERVE(4)