afs: Convert to separately allocated bdi

Allocate struct backing_dev_info separately instead of embedding it
inside the superblock. This unifies handling of bdi among users.

CC: David Howells <dhowells@redhat.com>
CC: linux-afs@lists.infradead.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

fs/afs/internal.h

@@ -318,7 +318,6 @@ struct afs_volume {
 	unsigned short		rjservers;	/* number of servers discarded due to -ENOMEDIUM */
 	struct afs_server	*servers[8];	/* servers on which volume resides (ordered) */
 	struct rw_semaphore	server_sem;	/* lock for accessing current server */
-	struct backing_dev_info	bdi;
 };
 
 /*

fs/afs/super.c

@@ -319,7 +319,10 @@ static int afs_fill_super(struct super_block *sb,
 	sb->s_blocksize_bits	= PAGE_SHIFT;
 	sb->s_magic		= AFS_FS_MAGIC;
 	sb->s_op		= &afs_super_ops;
-	sb->s_bdi		= &as->volume->bdi;
+	ret = super_setup_bdi(sb);
+	if (ret)
+		return ret;
+	sb->s_bdi->ra_pages	= VM_MAX_READAHEAD * 1024 / PAGE_SIZE;
 	strlcpy(sb->s_id, as->volume->vlocation->vldb.name, sizeof(sb->s_id));
 
 	/* allocate the root inode and dentry */

fs/afs/volume.c

@@ -106,11 +106,6 @@ struct afs_volume *afs_volume_lookup(struct afs_mount_params *params)
 	volume->cell		= params->cell;
 	volume->vid		= vlocation->vldb.vid[params->type];
 
-	volume->bdi.ra_pages	= VM_MAX_READAHEAD*1024/PAGE_SIZE; 
-	ret = bdi_setup_and_register(&volume->bdi, "afs");
-	if (ret)
-		goto error_bdi;
-
 	init_rwsem(&volume->server_sem);
 
 	/* look up all the applicable server records */
@@ -156,8 +151,6 @@ struct afs_volume *afs_volume_lookup(struct afs_mount_params *params)
 	return ERR_PTR(ret);
 
 error_discard:
-	bdi_destroy(&volume->bdi);
-error_bdi:
 	up_write(&params->cell->vl_sem);
 
 	for (loop = volume->nservers - 1; loop >= 0; loop--)
@@ -207,7 +200,6 @@ void afs_put_volume(struct afs_volume *volume)
 	for (loop = volume->nservers - 1; loop >= 0; loop--)
 		afs_put_server(volume->servers[loop]);
 
-	bdi_destroy(&volume->bdi);
 	kfree(volume);
 
 	_leave(" [destroyed]");