blkcg: separate blkcg_conf_get_disk() out of blkg_conf_prep()

Separate out blkcg_conf_get_disk() so that it can be used by blkcg
policy interface file input parsers before the policy is actually
enabled.  This doesn't introduce any functional changes.

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

1 files changed, 43 insertions, 19 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 78ccbdcfe723..0e2619c1a422 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -755,6 +755,44 @@ static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg,
 
 /**
  * blkg_conf_prep - parse and prepare for per-blkg config update
+ * @inputp: input string pointer
+ *
+ * Parse the device node prefix part, MAJ:MIN, of per-blkg config update
+ * from @input and get and return the matching gendisk.  *@inputp is
+ * updated to point past the device node prefix.  Returns an ERR_PTR()
+ * value on error.
+ *
+ * Use this function iff blkg_conf_prep() can't be used for some reason.
+ */
+struct gendisk *blkcg_conf_get_disk(char **inputp)
+{
+        char *input = *inputp;
+        unsigned int major, minor;
+        struct gendisk *disk;
+        int key_len, part;
+
+        if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
+                return ERR_PTR(-EINVAL);
+
+        input += key_len;
+        if (!isspace(*input))
+                return ERR_PTR(-EINVAL);
+        input = skip_spaces(input);
+
+        disk = get_gendisk(MKDEV(major, minor), &part);
+        if (!disk)
+                return ERR_PTR(-ENODEV);
+        if (part) {
+                put_disk_and_module(disk);
+                return ERR_PTR(-ENODEV);
+        }
+
+        *inputp = input;
+        return disk;
+}
+
+/**
+ * blkg_conf_prep - parse and prepare for per-blkg config update
  * @blkcg: target block cgroup
  * @pol: target policy
  * @input: input string
@@ -772,25 +810,11 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
         struct gendisk *disk;
         struct request_queue *q;
         struct blkcg_gq *blkg;
-        unsigned int major, minor;
-        int key_len, part, ret;
-        char *body;
-
-        if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
-                return -EINVAL;
-
-        body = input + key_len;
-        if (!isspace(*body))
-                return -EINVAL;
-        body = skip_spaces(body);
+        int ret;
 
-        disk = get_gendisk(MKDEV(major, minor), &part);
-        if (!disk)
-                return -ENODEV;
-        if (part) {
-                ret = -ENODEV;
-                goto fail;
-        }
+        disk = blkcg_conf_get_disk(&input);
+        if (IS_ERR(disk))
+                return PTR_ERR(disk);
 
         q = disk->queue;
 
@@ -856,7 +880,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 success:
         ctx->disk = disk;
         ctx->blkg = blkg;
-        ctx->body = body;
+        ctx->body = input;
         return 0;
 
 fail_unlock: