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lru_cache: allow multiple changes per transaction

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Allow multiple changes to the active set of elements in lru_cache.
The only current user of lru_cache, drbd, is driving this generalisation.

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 13:21:01 +01:00
committed by Philipp Reisner
parent 45dfffebd0
commit 46a15bc3ec
4 changed files with 226 additions and 141 deletions
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70
include/linux/lru_cache.h
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@@ -166,9 +166,11 @@ struct lc_element {
/* if we want to track a larger set of objects,
* it needs to become arch independend u64 */
unsigned lc_number;
/* special label when on free list */
#define LC_FREE (~0U)
/* for pending changes */
unsigned lc_new_number;
};
struct lru_cache {
@@ -176,6 +178,7 @@ struct lru_cache {
struct list_head lru;
struct list_head free;
struct list_head in_use;
struct list_head to_be_changed;
/* the pre-created kmem cache to allocate the objects from */
struct kmem_cache *lc_cache;
@@ -186,7 +189,7 @@ struct lru_cache {
size_t element_off;
/* number of elements (indices) */
unsigned int nr_elements;
unsigned int nr_elements;
/* Arbitrary limit on maximum tracked objects. Practical limit is much
* lower due to allocation failures, probably. For typical use cases,
* nr_elements should be a few thousand at most.
@@ -194,18 +197,19 @@ struct lru_cache {
* 8 high bits of .lc_index to be overloaded with flags in the future. */
#define LC_MAX_ACTIVE (1<<24)
/* allow to accumulate a few (index:label) changes,
* but no more than max_pending_changes */
unsigned int max_pending_changes;
/* number of elements currently on to_be_changed list */
unsigned int pending_changes;
/* statistics */
unsigned used; /* number of lelements currently on in_use list */
unsigned long hits, misses, starving, dirty, changed;
unsigned used; /* number of elements currently on in_use list */
unsigned long hits, misses, starving, locked, changed;
/* see below: flag-bits for lru_cache */
unsigned long flags;
/* when changing the label of an index element */
unsigned int new_number;
/* for paranoia when changing the label of an index element */
struct lc_element *changing_element;
void *lc_private;
const char *name;
@@ -221,10 +225,15 @@ enum {
/* debugging aid, to catch concurrent access early.
* user needs to guarantee exclusive access by proper locking! */
__LC_PARANOIA,
/* if we need to change the set, but currently there is a changing
* transaction pending, we are "dirty", and must deferr further
* changing requests */
/* annotate that the set is "dirty", possibly accumulating further
* changes, until a transaction is finally triggered */
__LC_DIRTY,
/* Locked, no further changes allowed.
* Also used to serialize changing transactions. */
__LC_LOCKED,
/* if we need to change the set, but currently there is no free nor
* unused element available, we are "starving", and must not give out
* further references, to guarantee that eventually some refcnt will
@@ -236,9 +245,11 @@ enum {
};
#define LC_PARANOIA (1<<__LC_PARANOIA)
#define LC_DIRTY (1<<__LC_DIRTY)
#define LC_LOCKED (1<<__LC_LOCKED)
#define LC_STARVING (1<<__LC_STARVING)
extern struct lru_cache *lc_create(const char *name, struct kmem_cache *cache,
unsigned max_pending_changes,
unsigned e_count, size_t e_size, size_t e_off);
extern void lc_reset(struct lru_cache *lc);
extern void lc_destroy(struct lru_cache *lc);
@@ -249,7 +260,7 @@ extern struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr);
extern struct lc_element *lc_find(struct lru_cache *lc, unsigned int enr);
extern struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr);
extern unsigned int lc_put(struct lru_cache *lc, struct lc_element *e);
extern void lc_changed(struct lru_cache *lc, struct lc_element *e);
extern void lc_committed(struct lru_cache *lc);
struct seq_file;
extern size_t lc_seq_printf_stats(struct seq_file *seq, struct lru_cache *lc);
@@ -258,16 +269,28 @@ extern void lc_seq_dump_details(struct seq_file *seq, struct lru_cache *lc, char
void (*detail) (struct seq_file *, struct lc_element *));
/**
* lc_try_lock - can be used to stop lc_get() from changing the tracked set
* lc_try_lock_for_transaction - can be used to stop lc_get() from changing the tracked set
* @lc: the lru cache to operate on
*
* Allows (expects) the set to be "dirty". Note that the reference counts and
* order on the active and lru lists may still change. Used to serialize
* changing transactions. Returns true if we aquired the lock.
*/
static inline int lc_try_lock_for_transaction(struct lru_cache *lc)
{
return !test_and_set_bit(__LC_LOCKED, &lc->flags);
}
/**
* lc_try_lock - variant to stop lc_get() from changing the tracked set
* @lc: the lru cache to operate on
*
* Note that the reference counts and order on the active and lru lists may
* still change. Returns true if we acquired the lock.
* still change. Only works on a "clean" set. Returns true if we aquired the
* lock, which means there are no pending changes, and any further attempt to
* change the set will not succeed until the next lc_unlock().
*/
static inline int lc_try_lock(struct lru_cache *lc)
{
return !test_and_set_bit(__LC_DIRTY, &lc->flags);
}
extern int lc_try_lock(struct lru_cache *lc);
/**
* lc_unlock - unlock @lc, allow lc_get() to change the set again
@@ -275,14 +298,11 @@ static inline int lc_try_lock(struct lru_cache *lc)
*/
static inline void lc_unlock(struct lru_cache *lc)
{
clear_bit_unlock(__LC_DIRTY, &lc->flags);
clear_bit(__LC_DIRTY, &lc->flags);
clear_bit_unlock(__LC_LOCKED, &lc->flags);
}
static inline int lc_is_used(struct lru_cache *lc, unsigned int enr)
{
struct lc_element *e = lc_find(lc, enr);
return e && e->refcnt;
}
extern bool lc_is_used(struct lru_cache *lc, unsigned int enr);
#define lc_entry(ptr, type, member) \
container_of(ptr, type, member)