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dm cache: Add some documentation to dm-cache-background-tracker.h 

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Joe Thornber 2023-01-26 10:14:26 +00:00 committed by Mike Snitzer
parent 95ab80a8a0
commit 22c40e134c
1 changed files with 37 additions and 3 deletions
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40
drivers/md/dm-cache-background-tracker.h
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@ -12,19 +12,44 @@
/*----------------------------------------------------------------*/
/*
* The cache policy decides what background work should be performed,
* such as promotions, demotions and writebacks. The core cache target
* is in charge of performing the work, and does so when it sees fit.
*
* The background_tracker acts as a go between. Keeping track of future
* work that the policy has decided upon, and handing (issuing) it to
* the core target when requested.
*
* There is no locking in this, so calls will probably need to be
* protected with a spinlock.
*/
struct background_work;
struct background_tracker;
/*
* FIXME: discuss lack of locking in all methods.
* Create a new tracker, it will not be able to queue more than
* 'max_work' entries.
*/
struct background_tracker *btracker_create(unsigned max_work);
/*
* Destroy the tracker. No issued, but not complete, work should
* exist when this is called. It is fine to have queued but unissued
* work.
*/
void btracker_destroy(struct background_tracker *b);
unsigned btracker_nr_writebacks_queued(struct background_tracker *b);
unsigned btracker_nr_demotions_queued(struct background_tracker *b);
/*
* Queue some work within the tracker. 'work' should point to the work
* to queue, this will be copied (ownership doesn't pass). If pwork
* is not NULL then it will be set to point to the tracker's internal
* copy of the work.
*
* returns -EINVAL iff the work is already queued. -ENOMEM if the work
* couldn't be queued for another reason.
*/
@ -33,11 +58,20 @@ int btracker_queue(struct background_tracker *b,
struct policy_work **pwork);
/*
* Hands out the next piece of work to be performed.
* Returns -ENODATA if there's no work.
*/
int btracker_issue(struct background_tracker *b, struct policy_work **work);
void btracker_complete(struct background_tracker *b,
struct policy_work *op);
/*
* Informs the tracker that the work has been completed and it may forget
* about it.
*/
void btracker_complete(struct background_tracker *b, struct policy_work *op);
/*
* Predicate to see if an origin block is already scheduled for promotion.
*/
bool btracker_promotion_already_present(struct background_tracker *b,
dm_oblock_t oblock);