block: fix genhd refcounting in blkio_policy_parse_and_set()

blkio_policy_parse_and_set() calls blkio_check_dev_num() to check
whether the given dev_t is valid.  blkio_check_dev_num() uses
get_gendisk() for verification but never puts the returned genhd
leaking the reference.

This patch collapses blkio_check_dev_num() into its caller and updates
it such that the genhd is put before returning.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 23 insertions, 33 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b596e54ddd7..d61ec5636ce 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -768,25 +768,14 @@ static uint64_t blkio_get_stat(struct blkio_group *blkg,
         return disk_total;
 }
 
-static int blkio_check_dev_num(dev_t dev)
-{
-        int part = 0;
-        struct gendisk *disk;
-
-        disk = get_gendisk(dev, &part);
-        if (!disk || part)
-                return -ENODEV;
-
-        return 0;
-}
-
 static int blkio_policy_parse_and_set(char *buf,
         struct blkio_policy_node *newpn, enum blkio_policy_id plid, int fileid)
 {
+        struct gendisk *disk = NULL;
         char *s[4], *p, *major_s = NULL, *minor_s = NULL;
-        int ret;
         unsigned long major, minor;
-        int i = 0;
+        int i = 0, ret = -EINVAL;
+        int part;
         dev_t dev;
         u64 temp;
 
@@ -804,37 +793,36 @@ static int blkio_policy_parse_and_set(char *buf,
         }
 
         if (i != 2)
-                return -EINVAL;
+                goto out;
 
         p = strsep(&s[0], ":");
         if (p != NULL)
                 major_s = p;
         else
-                return -EINVAL;
+                goto out;
 
         minor_s = s[0];
         if (!minor_s)
-                return -EINVAL;
+                goto out;
 
-        ret = strict_strtoul(major_s, 10, &major);
-        if (ret)
-                return -EINVAL;
+        if (strict_strtoul(major_s, 10, &major))
+                goto out;
 
-        ret = strict_strtoul(minor_s, 10, &minor);
-        if (ret)
-                return -EINVAL;
+        if (strict_strtoul(minor_s, 10, &minor))
+                goto out;
 
         dev = MKDEV(major, minor);
 
-        ret = strict_strtoull(s[1], 10, &temp);
-        if (ret)
-                return -EINVAL;
+        if (strict_strtoull(s[1], 10, &temp))
+                goto out;
 
         /* For rule removal, do not check for device presence. */
         if (temp) {
-                ret = blkio_check_dev_num(dev);
-                if (ret)
-                        return ret;
+                disk = get_gendisk(dev, &part);
+                if (!disk || part) {
+                        ret = -ENODEV;
+                        goto out;
+                }
         }
 
         newpn->dev = dev;
@@ -843,7 +831,7 @@ static int blkio_policy_parse_and_set(char *buf,
         case BLKIO_POLICY_PROP:
                 if ((temp < BLKIO_WEIGHT_MIN && temp > 0) ||
                      temp > BLKIO_WEIGHT_MAX)
-                        return -EINVAL;
+                        goto out;
 
                 newpn->plid = plid;
                 newpn->fileid = fileid;
@@ -860,7 +848,7 @@ static int blkio_policy_parse_and_set(char *buf,
                 case BLKIO_THROTL_read_iops_device:
                 case BLKIO_THROTL_write_iops_device:
                         if (temp > THROTL_IOPS_MAX)
-                                return -EINVAL;
+                                goto out;
 
                         newpn->plid = plid;
                         newpn->fileid = fileid;
@@ -871,8 +859,10 @@ static int blkio_policy_parse_and_set(char *buf,
         default:
                 BUG();
         }
-
-        return 0;
+        ret = 0;
+out:
+        put_disk(disk);
+        return ret;
 }
 
 unsigned int blkcg_get_weight(struct blkio_cgroup *blkcg,