block: move __dev from disk to part0

Move disk->__dev to part0->__dev.  This simplifies bdget_disk() and
lookup_devt() and allows common sysfs attributes to be unified.
part_to_disk() is updated to handle part0 -> disk.

Updated to include a fix from Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>,
he writes:

"part0 is a "special" partition and doesn't need to have capacity set - this
fixes regression caused by "block: move __dev from disk to part0" commit."

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

1 files changed, 12 insertions, 28 deletions

diff --git a/block/genhd.c b/block/genhd.c
index 65b7386c26d8..36b9f1bdd91f 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -537,22 +537,15 @@ struct gendisk *get_gendisk(dev_t devt, int *partno)
  */
 extern struct block_device *bdget_disk(struct gendisk *disk, int partno)
 {
-        dev_t devt = MKDEV(0, 0);
+        struct hd_struct *part;
+        struct block_device *bdev = NULL;
 
-        if (partno == 0)
-                devt = disk_devt(disk);
-        else {
-                struct hd_struct *part;
+        part = disk_get_part(disk, partno);
+        if (part && (part->nr_sects || partno == 0))
+                bdev = bdget(part_devt(part));
+        disk_put_part(part);
 
-                part = disk_get_part(disk, partno);
-                if (part && part->nr_sects)
-                        devt = part_devt(part);
-                disk_put_part(part);
-        }
-
-        if (likely(devt != MKDEV(0, 0)))
-                return bdget(devt);
-        return NULL;
+        return bdev;
 }
 EXPORT_SYMBOL(bdget_disk);
 
@@ -1000,27 +993,18 @@ dev_t blk_lookup_devt(const char *name, int partno)
         class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
         while ((dev = class_dev_iter_next(&iter))) {
                 struct gendisk *disk = dev_to_disk(dev);
+                struct hd_struct *part;
 
                 if (strcmp(dev->bus_id, name))
                         continue;
-                if (partno < 0 || partno >= disk_max_parts(disk))
-                        continue;
-
-                if (partno == 0)
-                        devt = disk_devt(disk);
-                else {
-                        struct hd_struct *part;
-
-                        part = disk_get_part(disk, partno);
-                        if (!part || !part->nr_sects) {
-                                disk_put_part(part);
-                                continue;
-                        }
 
+                part = disk_get_part(disk, partno);
+                if (part && (part->nr_sects || partno == 0)) {
                         devt = part_devt(part);
                         disk_put_part(part);
+                        break;
                 }
-                break;
+                disk_put_part(part);
         }
         class_dev_iter_exit(&iter);
         return devt;