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rbd: add target object existence flags 

This creates two new flags for object requests to indicate what is
known about the existence of the object to which a request is to be
sent.  The KNOWN flag will be true if the the EXISTS flag is
meaningful.  That is:

    KNOWN   EXISTS
    -----   ------
      0       0     don't know whether the object exists
      0       1     (not used/invalid)
      1       0     object is known to not exist
      1       0     object is known to exist

This will be used in determining how to handle write requests for
data objects for layered rbd images.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
This commit is contained in:
Alex Elder 2013-02-11 12:33:24 -06:00 committed by Sage Weil
parent 57acbaa7fb
commit 5679c59f60
1 changed files with 37 additions and 0 deletions
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37
drivers/block/rbd.c
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@ -173,6 +173,8 @@ enum obj_request_type {
enum obj_req_flags {
OBJ_REQ_DONE, /* completion flag: not done = 0, done = 1 */
OBJ_REQ_IMG_DATA, /* object usage: standalone = 0, image = 1 */
OBJ_REQ_KNOWN, /* EXISTS flag valid: no = 0, yes = 1 */
OBJ_REQ_EXISTS, /* target exists: no = 0, yes = 1 */
};
struct rbd_obj_request {
@ -1129,6 +1131,37 @@ static bool obj_request_done_test(struct rbd_obj_request *obj_request)
return test_bit(OBJ_REQ_DONE, &obj_request->flags) != 0;
}
/*
* This sets the KNOWN flag after (possibly) setting the EXISTS
* flag. The latter is set based on the "exists" value provided.
*
* Note that for our purposes once an object exists it never goes
* away again. It's possible that the response from two existence
* checks are separated by the creation of the target object, and
* the first ("doesn't exist") response arrives *after* the second
* ("does exist"). In that case we ignore the second one.
*/
static void obj_request_existence_set(struct rbd_obj_request *obj_request,
bool exists)
{
if (exists)
set_bit(OBJ_REQ_EXISTS, &obj_request->flags);
set_bit(OBJ_REQ_KNOWN, &obj_request->flags);
smp_mb();
}
static bool obj_request_known_test(struct rbd_obj_request *obj_request)
{
smp_mb();
return test_bit(OBJ_REQ_KNOWN, &obj_request->flags) != 0;
}
static bool obj_request_exists_test(struct rbd_obj_request *obj_request)
{
smp_mb();
return test_bit(OBJ_REQ_EXISTS, &obj_request->flags) != 0;
}
static void rbd_obj_request_get(struct rbd_obj_request *obj_request)
{
dout("%s: obj %p (was %d)\n", __func__, obj_request,
@ -1623,6 +1656,10 @@ static struct rbd_img_request *rbd_img_request_create(
INIT_LIST_HEAD(&img_request->obj_requests);
kref_init(&img_request->kref);
(void) obj_request_existence_set;
(void) obj_request_known_test;
(void) obj_request_exists_test;
rbd_img_request_get(img_request); /* Avoid a warning */
rbd_img_request_put(img_request); /* TEMPORARY */