init: refactor name_to_dev_t

Split each case into a self-contained helper, and move the block
dependent code entirely under the pre-existing #ifdef CONFIG_BLOCK.
This allows to remove the blk_lookup_devt stub in genhd.h.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/genhd.h

@@ -388,18 +388,13 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev,
 }
 #endif /* CONFIG_SYSFS */
 
+dev_t blk_lookup_devt(const char *name, int partno);
 #ifdef CONFIG_BLOCK
 void printk_all_partitions(void);
-dev_t blk_lookup_devt(const char *name, int partno);
 #else /* CONFIG_BLOCK */
 static inline void printk_all_partitions(void)
 {
 }
-static inline dev_t blk_lookup_devt(const char *name, int partno)
-{
-	dev_t devt = MKDEV(0, 0);
-	return devt;
-}
 #endif /* CONFIG_BLOCK */
 
 #endif /* _LINUX_GENHD_H */

init/do_mounts.c

@@ -90,7 +90,6 @@ static int match_dev_by_uuid(struct device *dev, const void *data)
 	return 0;
 }
 
-
 /**
  * devt_from_partuuid - looks up the dev_t of a partition by its UUID
  * @uuid_str:	char array containing ascii UUID
@@ -186,7 +185,83 @@ static int match_dev_by_label(struct device *dev, const void *data)
 
 	return 0;
 }
-#endif
+
+static dev_t devt_from_partlabel(const char *label)
+{
+	struct device *dev;
+	dev_t devt = 0;
+
+	dev = class_find_device(&block_class, NULL, label, &match_dev_by_label);
+	if (dev) {
+		devt = dev->devt;
+		put_device(dev);
+	}
+
+	return devt;
+}
+
+static dev_t devt_from_devname(const char *name)
+{
+	dev_t devt = 0;
+	int part;
+	char s[32];
+	char *p;
+
+	if (strlen(name) > 31)
+		return 0;
+	strcpy(s, name);
+	for (p = s; *p; p++) {
+		if (*p == '/')
+			*p = '!';
+	}
+
+	devt = blk_lookup_devt(s, 0);
+	if (devt)
+		return devt;
+
+	/*
+	 * Try non-existent, but valid partition, which may only exist after
+	 * opening the device, like partitioned md devices.
+	 */
+	while (p > s && isdigit(p[-1]))
+		p--;
+	if (p == s || !*p || *p == '0')
+		return 0;
+
+	/* try disk name without <part number> */
+	part = simple_strtoul(p, NULL, 10);
+	*p = '\0';
+	devt = blk_lookup_devt(s, part);
+	if (devt)
+		return devt;
+
+	/* try disk name without p<part number> */
+	if (p < s + 2 || !isdigit(p[-2]) || p[-1] != 'p')
+		return 0;
+	p[-1] = '\0';
+	return blk_lookup_devt(s, part);
+}
+#endif /* CONFIG_BLOCK */
+
+static dev_t devt_from_devnum(const char *name)
+{
+	unsigned maj, min, offset;
+	dev_t devt = 0;
+	char *p, dummy;
+
+	if (sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2 ||
+	    sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset, &dummy) == 3) {
+		devt = MKDEV(maj, min);
+		if (maj != MAJOR(devt) || min != MINOR(devt))
+			return 0;
+	} else {
+		devt = new_decode_dev(simple_strtoul(name, &p, 16));
+		if (*p)
+			return 0;
+	}
+
+	return devt;
+}
 
 /*
  *	Convert a name into device number.  We accept the following variants:
@@ -218,101 +293,23 @@ static int match_dev_by_label(struct device *dev, const void *data)
  *	name contains slashes, the device name has them replaced with
  *	bangs.
  */
-
 dev_t name_to_dev_t(const char *name)
 {
-	char s[32];
-	char *p;
-	dev_t res = 0;
-	int part;
-
+	if (strcmp(name, "/dev/nfs") == 0)
+		return Root_NFS;
+	if (strcmp(name, "/dev/cifs") == 0)
+		return Root_CIFS;
+	if (strcmp(name, "/dev/ram") == 0)
+		return Root_RAM0;
 #ifdef CONFIG_BLOCK
-	if (strncmp(name, "PARTUUID=", 9) == 0) {
-		name += 9;
-		res = devt_from_partuuid(name);
-		if (!res)
-			goto fail;
-		goto done;
-	} else if (strncmp(name, "PARTLABEL=", 10) == 0) {
-		struct device *dev;
-
-		dev = class_find_device(&block_class, NULL, name + 10,
-					&match_dev_by_label);
-		if (!dev)
-			goto fail;
-
-		res = dev->devt;
-		put_device(dev);
-		goto done;
-	}
+	if (strncmp(name, "PARTUUID=", 9) == 0)
+		return devt_from_partuuid(name + 9);
+	if (strncmp(name, "PARTLABEL=", 10) == 0)
+		return devt_from_partlabel(name + 10);
+	if (strncmp(name, "/dev/", 5) == 0)
+		return devt_from_devname(name + 5);
 #endif
-
-	if (strncmp(name, "/dev/", 5) != 0) {
-		unsigned maj, min, offset;
-		char dummy;
-
-		if ((sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2) ||
-		    (sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset, &dummy) == 3)) {
-			res = MKDEV(maj, min);
-			if (maj != MAJOR(res) || min != MINOR(res))
-				goto fail;
-		} else {
-			res = new_decode_dev(simple_strtoul(name, &p, 16));
-			if (*p)
-				goto fail;
-		}
-		goto done;
-	}
-
-	name += 5;
-	res = Root_NFS;
-	if (strcmp(name, "nfs") == 0)
-		goto done;
-	res = Root_CIFS;
-	if (strcmp(name, "cifs") == 0)
-		goto done;
-	res = Root_RAM0;
-	if (strcmp(name, "ram") == 0)
-		goto done;
-
-	if (strlen(name) > 31)
-		goto fail;
-	strcpy(s, name);
-	for (p = s; *p; p++)
-		if (*p == '/')
-			*p = '!';
-	res = blk_lookup_devt(s, 0);
-	if (res)
-		goto done;
-
-	/*
-	 * try non-existent, but valid partition, which may only exist
-	 * after revalidating the disk, like partitioned md devices
-	 */
-	while (p > s && isdigit(p[-1]))
-		p--;
-	if (p == s || !*p || *p == '0')
-		goto fail;
-
-	/* try disk name without <part number> */
-	part = simple_strtoul(p, NULL, 10);
-	*p = '\0';
-	res = blk_lookup_devt(s, part);
-	if (res)
-		goto done;
-
-	/* try disk name without p<part number> */
-	if (p < s + 2 || !isdigit(p[-2]) || p[-1] != 'p')
-		goto fail;
-	p[-1] = '\0';
-	res = blk_lookup_devt(s, part);
-	if (res)
-		goto done;
-
-fail:
-	return 0;
-done:
-	return res;
+	return devt_from_devnum(name);
 }
 EXPORT_SYMBOL_GPL(name_to_dev_t);