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Commit c66c6e0c authored by Alex Elder's avatar Alex Elder Committed by Alex Elder
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rbd: document rbd_spec structure 



I promised Josh I would document whether there were any restrictions
needed for accessing fields of an rbd_spec structure.  This adds a
big block of comments that documents the structure and how it is
used--including the fact that we don't attempt to synchronize access
to it.

Signed-off-by: default avatarAlex Elder <elder@inktank.com>
Reviewed-by: default avatarDavid Zafman <david.zafman@inktank.com>
Reviewed-by: default avatarJosh Durgin <josh.durgin@inktank.com>
parent c3acb181

drivers/block/rbd.c

+20 −1
Original line number Diff line number Diff line
@@ -119,7 +119,26 @@ struct rbd_image_header { 
 * An rbd image specification.

 *

 * The tuple (pool_id, image_id, snap_id) is sufficient to uniquely

 * identify an image.

 * identify an image.  Each rbd_dev structure includes a pointer to

 * an rbd_spec structure that encapsulates this identity.

 *

 * Each of the id's in an rbd_spec has an associated name.  For a

 * user-mapped image, the names are supplied and the id's associated

 * with them are looked up.  For a layered image, a parent image is

 * defined by the tuple, and the names are looked up.

 *

 * An rbd_dev structure contains a parent_spec pointer which is

 * non-null if the image it represents is a child in a layered

 * image.  This pointer will refer to the rbd_spec structure used

 * by the parent rbd_dev for its own identity (i.e., the structure

 * is shared between the parent and child).

 *

 * Since these structures are populated once, during the discovery

 * phase of image construction, they are effectively immutable so

 * we make no effort to synchronize access to them.

 *

 * Note that code herein does not assume the image name is known (it

 * could be a null pointer).

 */

struct rbd_spec {

	u64		pool_id;