printk(KERN_ERR f); \
printk("\n"); \
} while(0)
+
+#define MB_CACHE_WRITER ((unsigned short)~0U >> 1)
+
+DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>");
MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
EXPORT_SYMBOL(mb_cache_entry_alloc);
EXPORT_SYMBOL(mb_cache_entry_insert);
EXPORT_SYMBOL(mb_cache_entry_release);
-EXPORT_SYMBOL(mb_cache_entry_takeout);
EXPORT_SYMBOL(mb_cache_entry_free);
-EXPORT_SYMBOL(mb_cache_entry_dup);
EXPORT_SYMBOL(mb_cache_entry_get);
#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
EXPORT_SYMBOL(mb_cache_entry_find_first);
EXPORT_SYMBOL(mb_cache_entry_find_next);
#endif
+struct mb_cache {
+ struct list_head c_cache_list;
+ const char *c_name;
+ struct mb_cache_op c_op;
+ atomic_t c_entry_count;
+ int c_bucket_bits;
+#ifndef MB_CACHE_INDEXES_COUNT
+ int c_indexes_count;
+#endif
+ kmem_cache_t *c_entry_cache;
+ struct list_head *c_block_hash;
+ struct list_head *c_indexes_hash[0];
+};
+
/*
* Global data: list of all mbcache's, lru list, and a spinlock for
static LIST_HEAD(mb_cache_list);
static LIST_HEAD(mb_cache_lru_list);
-static spinlock_t mb_cache_spinlock = SPIN_LOCK_UNLOCKED;
+static DEFINE_SPINLOCK(mb_cache_spinlock);
static struct shrinker *mb_shrinker;
static inline int
{
struct mb_cache *cache = ce->e_cache;
- mb_assert(atomic_read(&ce->e_used) == 0);
+ mb_assert(!(ce->e_used || ce->e_queued));
if (cache->c_op.free && cache->c_op.free(ce, gfp_mask)) {
/* free failed -- put back on the lru list
for freeing later. */
static inline void
__mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
{
- if (atomic_dec_and_test(&ce->e_used)) {
+ /* Wake up all processes queuing for this cache entry. */
+ if (ce->e_queued)
+ wake_up_all(&mb_cache_queue);
+ if (ce->e_used >= MB_CACHE_WRITER)
+ ce->e_used -= MB_CACHE_WRITER;
+ ce->e_used--;
+ if (!(ce->e_used || ce->e_queued)) {
if (!__mb_cache_entry_is_hashed(ce))
goto forget;
+ mb_assert(list_empty(&ce->e_lru_list));
list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
}
spin_unlock(&mb_cache_spinlock);
struct mb_cache *cache = NULL;
if(entry_size < sizeof(struct mb_cache_entry) +
- indexes_count * sizeof(struct mb_cache_entry_index))
+ indexes_count * sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]))
return NULL;
cache = kmalloc(sizeof(struct mb_cache) +
INIT_LIST_HEAD(&ce->e_lru_list);
INIT_LIST_HEAD(&ce->e_block_list);
ce->e_cache = cache;
- atomic_set(&ce->e_used, 1);
+ ce->e_used = 1 + MB_CACHE_WRITER;
+ ce->e_queued = 0;
}
return ce;
}
}
-/*
- * mb_cache_entry_takeout()
- *
- * Take a cache entry out of the cache, making it invalid. The entry can later
- * be re-inserted using mb_cache_entry_insert(), or released using
- * mb_cache_entry_release().
- */
-void
-mb_cache_entry_takeout(struct mb_cache_entry *ce)
-{
- spin_lock(&mb_cache_spinlock);
- mb_assert(list_empty(&ce->e_lru_list));
- __mb_cache_entry_unhash(ce);
- spin_unlock(&mb_cache_spinlock);
-}
-
-
/*
* mb_cache_entry_free()
*
}
-/*
- * mb_cache_entry_dup()
- *
- * Duplicate a handle to a cache entry (does not duplicate the cache entry
- * itself). After the call, both the old and the new handle must be released.
- */
-struct mb_cache_entry *
-mb_cache_entry_dup(struct mb_cache_entry *ce)
-{
- atomic_inc(&ce->e_used);
- return ce;
-}
-
-
/*
* mb_cache_entry_get()
*
* Get a cache entry by device / block number. (There can only be one entry
* in the cache per device and block.) Returns NULL if no such cache entry
- * exists.
+ * exists. The returned cache entry is locked for exclusive access ("single
+ * writer").
*/
struct mb_cache_entry *
mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
list_for_each(l, &cache->c_block_hash[bucket]) {
ce = list_entry(l, struct mb_cache_entry, e_block_list);
if (ce->e_bdev == bdev && ce->e_block == block) {
+ DEFINE_WAIT(wait);
+
if (!list_empty(&ce->e_lru_list))
list_del_init(&ce->e_lru_list);
- atomic_inc(&ce->e_used);
+
+ while (ce->e_used > 0) {
+ ce->e_queued++;
+ prepare_to_wait(&mb_cache_queue, &wait,
+ TASK_UNINTERRUPTIBLE);
+ spin_unlock(&mb_cache_spinlock);
+ schedule();
+ spin_lock(&mb_cache_spinlock);
+ ce->e_queued--;
+ }
+ finish_wait(&mb_cache_queue, &wait);
+ ce->e_used += 1 + MB_CACHE_WRITER;
+
+ if (!__mb_cache_entry_is_hashed(ce)) {
+ __mb_cache_entry_release_unlock(ce);
+ return NULL;
+ }
goto cleanup;
}
}
list_entry(l, struct mb_cache_entry,
e_indexes[index].o_list);
if (ce->e_bdev == bdev && ce->e_indexes[index].o_key == key) {
+ DEFINE_WAIT(wait);
+
if (!list_empty(&ce->e_lru_list))
list_del_init(&ce->e_lru_list);
- atomic_inc(&ce->e_used);
+
+ /* Incrementing before holding the lock gives readers
+ priority over writers. */
+ ce->e_used++;
+ while (ce->e_used >= MB_CACHE_WRITER) {
+ ce->e_queued++;
+ prepare_to_wait(&mb_cache_queue, &wait,
+ TASK_UNINTERRUPTIBLE);
+ spin_unlock(&mb_cache_spinlock);
+ schedule();
+ spin_lock(&mb_cache_spinlock);
+ ce->e_queued--;
+ }
+ finish_wait(&mb_cache_queue, &wait);
+
+ if (!__mb_cache_entry_is_hashed(ce)) {
+ __mb_cache_entry_release_unlock(ce);
+ spin_lock(&mb_cache_spinlock);
+ return ERR_PTR(-EAGAIN);
+ }
return ce;
}
l = l->next;
*
* Find the first cache entry on a given device with a certain key in
* an additional index. Additonal matches can be found with
- * mb_cache_entry_find_next(). Returns NULL if no match was found.
+ * mb_cache_entry_find_next(). Returns NULL if no match was found. The
+ * returned cache entry is locked for shared access ("multiple readers").
*
* @cache: the cache to search
* @index: the number of the additonal index to search (0<=index<indexes_count)
git://git.onelab.eu / linux-2.6.git / blobdiff