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lru_cache: consolidate lc_get and lc_try_get

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Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2011-02-21 13:20:58 +01:00 committed by Philipp Reisner
parent 0097f0405d
commit a9efc748d6
1 changed files with 69 additions and 67 deletions
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136
lib/lru_cache.c
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@ -308,6 +308,58 @@ static int lc_unused_element_available(struct lru_cache *lc)
return 0; return 0;
} }
static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, bool may_change)
{
struct lc_element *e;
PARANOIA_ENTRY();
if (lc->flags & LC_STARVING) {
++lc->starving;
RETURN(NULL);
}
e = lc_find(lc, enr);
if (e) {
++lc->hits;
if (e->refcnt++ == 0)
lc->used++;
list_move(&e->list, &lc->in_use); /* Not evictable... */
RETURN(e);
}
++lc->misses;
if (!may_change)
RETURN(NULL);
/* In case there is nothing available and we can not kick out
* the LRU element, we have to wait ...
*/
if (!lc_unused_element_available(lc)) {
__set_bit(__LC_STARVING, &lc->flags);
RETURN(NULL);
}
/* it was not present in the active set.
* we are going to recycle an unused (or even "free") element.
* user may need to commit a transaction to record that change.
* we serialize on flags & LC_DIRTY */
if (test_and_set_bit(__LC_DIRTY, &lc->flags)) {
++lc->dirty;
RETURN(NULL);
}
e = lc_get_unused_element(lc);
BUG_ON(!e);
clear_bit(__LC_STARVING, &lc->flags);
BUG_ON(++e->refcnt != 1);
lc->used++;
lc->changing_element = e;
lc->new_number = enr;
RETURN(e);
}
/** /**
* lc_get - get element by label, maybe change the active set * lc_get - get element by label, maybe change the active set
@ -348,78 +400,28 @@ static int lc_unused_element_available(struct lru_cache *lc)
*/ */
struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr) struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr)
{ {
struct lc_element *e; return __lc_get(lc, enr, 1);
PARANOIA_ENTRY();
if (lc->flags & LC_STARVING) {
++lc->starving;
RETURN(NULL);
} }
e = lc_find(lc, enr); /**
if (e) { * lc_try_get - get element by label, if present; do not change the active set
++lc->hits; * @lc: the lru cache to operate on
if (e->refcnt++ == 0) * @enr: the label to look up
lc->used++; *
list_move(&e->list, &lc->in_use); /* Not evictable... */ * Finds an element in the cache, increases its usage count,
RETURN(e); * "touches" and returns it.
} *
* Return values:
++lc->misses; * NULL
* The cache was marked %LC_STARVING,
/* In case there is nothing available and we can not kick out * or the requested label was not in the active set
* the LRU element, we have to wait ... *
*/ * pointer to the element with the REQUESTED element number.
if (!lc_unused_element_available(lc)) { * In this case, it can be used right away
__set_bit(__LC_STARVING, &lc->flags);
RETURN(NULL);
}
/* it was not present in the active set.
* we are going to recycle an unused (or even "free") element.
* user may need to commit a transaction to record that change.
* we serialize on flags & LC_DIRTY */
if (test_and_set_bit(__LC_DIRTY, &lc->flags)) {
++lc->dirty;
RETURN(NULL);
}
e = lc_get_unused_element(lc);
BUG_ON(!e);
clear_bit(__LC_STARVING, &lc->flags);
BUG_ON(++e->refcnt != 1);
lc->used++;
lc->changing_element = e;
lc->new_number = enr;
RETURN(e);
}
/* similar to lc_get,
* but only gets a new reference on an existing element.
* you either get the requested element, or NULL.
* will be consolidated into one function.
*/ */
struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr) struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr)
{ {
struct lc_element *e; return __lc_get(lc, enr, 0);
PARANOIA_ENTRY();
if (lc->flags & LC_STARVING) {
++lc->starving;
RETURN(NULL);
}
e = lc_find(lc, enr);
if (e) {
++lc->hits;
if (e->refcnt++ == 0)
lc->used++;
list_move(&e->list, &lc->in_use); /* Not evictable... */
}
RETURN(e);
} }
/** /**