dm: add name and uuid to sysfs

Implement simple read-only sysfs entry for device-mapper block device.

This patch adds a simple sysfs directory named "dm" under block device
properties and implements
	- name attribute (string containing mapped device name)
	- uuid attribute (string containing UUID, or empty string if not set)

The kobject is embedded in mapped_device struct, so no additional
memory allocation is needed for initializing sysfs entry.

During the processing of sysfs attribute we need to lock mapped device
which is done by a new function dm_get_from_kobj, which returns the md
associated with kobject and increases the usage count.

Each 'show attribute' function is responsible for its own locking.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 9f9aa64f7336..51ba1db4b3e7 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2001, 2002 Sistina Software (UK) Limited.
- * Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
  *
  * This file is released under the GPL.
  */
@@ -167,6 +167,9 @@ struct mapped_device {
 
         /* forced geometry settings */
         struct hd_geometry geometry;
+
+        /* sysfs handle */
+        struct kobject kobj;
 };
 
 #define MIN_IOS 256
@@ -1285,6 +1288,8 @@ int dm_create(int minor, struct mapped_device **result)
         if (!md)
                 return -ENXIO;
 
+        dm_sysfs_init(md);
+
         *result = md;
         return 0;
 }
@@ -1360,6 +1365,7 @@ void dm_put(struct mapped_device *md)
                         dm_table_presuspend_targets(map);
                         dm_table_postsuspend_targets(map);
                 }
+                dm_sysfs_exit(md);
                 dm_table_put(map);
                 __unbind(md);
                 free_dev(md);
@@ -1699,6 +1705,27 @@ struct gendisk *dm_disk(struct mapped_device *md)
         return md->disk;
 }
 
+struct kobject *dm_kobject(struct mapped_device *md)
+{
+        return &md->kobj;
+}
+
+/*
+ * struct mapped_device should not be exported outside of dm.c
+ * so use this check to verify that kobj is part of md structure
+ */
+struct mapped_device *dm_get_from_kobject(struct kobject *kobj)
+{
+        struct mapped_device *md;
+
+        md = container_of(kobj, struct mapped_device, kobj);
+        if (&md->kobj != kobj)
+                return NULL;
+
+        dm_get(md);
+        return md;
+}
+
 int dm_suspended(struct mapped_device *md)
 {
         return test_bit(DMF_SUSPENDED, &md->flags);