diff options
Diffstat (limited to 'include/linux/lru_cache.h')
| -rw-r--r-- | include/linux/lru_cache.h | 71 |
1 files changed, 45 insertions, 26 deletions
diff --git a/include/linux/lru_cache.h b/include/linux/lru_cache.h index 7a71ffad037c..4019013c6593 100644 --- a/include/linux/lru_cache.h +++ b/include/linux/lru_cache.h @@ -52,8 +52,8 @@ We replicate IO (more or less synchronously) to local and remote disk. For crash recovery after replication node failure, we need to resync all regions that have been target of in-flight WRITE IO - (in use, or "hot", regions), as we don't know wether or not those WRITEs have - made it to stable storage. + (in use, or "hot", regions), as we don't know whether or not those WRITEs + have made it to stable storage. To avoid a "full resync", we need to persistently track these regions. @@ -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); @@ -258,32 +269,40 @@ 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 * - * Note that the reference counts and order on the active and lru lists may - * still change. Returns true if we acquired the lock. + * 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(struct lru_cache *lc) +static inline int lc_try_lock_for_transaction(struct lru_cache *lc) { - return !test_and_set_bit(__LC_DIRTY, &lc->flags); + 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. 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(). + */ +extern int lc_try_lock(struct lru_cache *lc); + +/** * lc_unlock - unlock @lc, allow lc_get() to change the set again * @lc: the lru cache to operate on */ static inline void lc_unlock(struct lru_cache *lc) { clear_bit(__LC_DIRTY, &lc->flags); - smp_mb__after_clear_bit(); + 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) |