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>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 78ccbdc..0e2619c 100644 (file)
--- 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:

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 261248e..bed9e43 100644 (file)
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -234,6 +234,7 @@ struct blkg_conf_ctx {
        char                            *body;
 };
 
+struct gendisk *blkcg_conf_get_disk(char **inputp);
 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
                   char *input, struct blkg_conf_ctx *ctx);
 void blkg_conf_finish(struct blkg_conf_ctx *ctx);