-/*------------------------ Short Operations Cache ------------------------------
- * In many situations where there is no high level buffering a lot of
- * reads might be short sequential reads, and a lot of writes may be short
- * sequential writes. eg. scanning/writing a jpeg file.
- * In these cases, a short read/write cache can provide a huge perfomance
- * benefit with dumb-as-a-rock code.
- * In Linux, the page cache provides read buffering and the short op cache
- * provides write buffering.
- *
- * There are a small number (~10) of cache chunks per device so that we don't
- * need a very intelligent search.
- */
-
-static int yaffs_obj_cache_dirty(struct yaffs_obj *obj)
-{
- struct yaffs_dev *dev = obj->my_dev;
- int i;
- struct yaffs_cache *cache;
- int n_caches = obj->my_dev->param.n_caches;
-
- for (i = 0; i < n_caches; i++) {
- cache = &dev->cache[i];
- if (cache->object == obj && cache->dirty)
- return 1;
- }
-
- return 0;
-}
-
-static void yaffs_flush_single_cache(struct yaffs_cache *cache, int discard)
-{
-
- if (!cache || cache->locked)
- return;
-
- /* Write it out and free it up if need be.*/
- if (cache->dirty) {
- yaffs_wr_data_obj(cache->object,
- cache->chunk_id,
- cache->data,
- cache->n_bytes,
- 1);
-
- cache->dirty = 0;
- }
-
- if (discard)
- cache->object = NULL;
-}
-
-static void yaffs_flush_file_cache(struct yaffs_obj *obj, int discard)
-{
- struct yaffs_dev *dev = obj->my_dev;
- int i;
- struct yaffs_cache *cache;
- int n_caches = obj->my_dev->param.n_caches;
-
- if (n_caches < 1)
- return;
-
-
- /* Find the chunks for this object and flush them. */
- for (i = 0; i < n_caches; i++) {
- cache = &dev->cache[i];
- if (cache->object == obj)
- yaffs_flush_single_cache(cache, discard);
- }
-
-}
-
-
-void yaffs_flush_whole_cache(struct yaffs_dev *dev, int discard)
-{
- struct yaffs_obj *obj;
- int n_caches = dev->param.n_caches;
- int i;
-
- /* Find a dirty object in the cache and flush it...
- * until there are no further dirty objects.
- */
- do {
- obj = NULL;
- for (i = 0; i < n_caches && !obj; i++) {
- if (dev->cache[i].object && dev->cache[i].dirty)
- obj = dev->cache[i].object;
- }
- if (obj)
- yaffs_flush_file_cache(obj, discard);
- } while (obj);
-
-}
-
-/* Grab us an unused cache chunk for use.
- * First look for an empty one.
- * Then look for the least recently used non-dirty one.
- * Then look for the least recently used dirty one...., flush and look again.
- */
-static struct yaffs_cache *yaffs_grab_chunk_worker(struct yaffs_dev *dev)
-{
- u32 i;
-
- if (dev->param.n_caches > 0) {
- for (i = 0; i < dev->param.n_caches; i++) {
- if (!dev->cache[i].object)
- return &dev->cache[i];
- }
- }
-
- return NULL;
-}
-
-static struct yaffs_cache *yaffs_grab_chunk_cache(struct yaffs_dev *dev)
-{
- struct yaffs_cache *cache;
- int usage;
- u32 i;
-
- if (dev->param.n_caches < 1)
- return NULL;
-
- /* First look for an unused cache */
-
- cache = yaffs_grab_chunk_worker(dev);
-
- if (cache)
- return cache;
-
- /*
- * Thery were all in use.
- * Find the LRU cache and flush it if it is dirty.
- */
-
- usage = -1;
- cache = NULL;
-
- for (i = 0; i < dev->param.n_caches; i++) {
- if (dev->cache[i].object &&
- !dev->cache[i].locked &&
- (dev->cache[i].last_use < usage || !cache)) {
- usage = dev->cache[i].last_use;
- cache = &dev->cache[i];
- }
- }
-
-#if 1
- yaffs_flush_single_cache(cache, 1);
-#else
- yaffs_flush_file_cache(cache->object, 1);
- cache = yaffs_grab_chunk_worker(dev);
-#endif
-
- return cache;
-}
-
-/* Find a cached chunk */
-static struct yaffs_cache *yaffs_find_chunk_cache(const struct yaffs_obj *obj,
- int chunk_id)
-{
- struct yaffs_dev *dev = obj->my_dev;
- u32 i;
-
- if (dev->param.n_caches < 1)
- return NULL;
-
- for (i = 0; i < dev->param.n_caches; i++) {
- if (dev->cache[i].object == obj &&
- dev->cache[i].chunk_id == chunk_id) {
- dev->cache_hits++;
-
- return &dev->cache[i];
- }
- }
- return NULL;
-}
-
-/* Mark the chunk for the least recently used algorithym */
-static void yaffs_use_cache(struct yaffs_dev *dev, struct yaffs_cache *cache,
- int is_write)
-{
- u32 i;
-
- if (dev->param.n_caches < 1)
- return;
-
- if (dev->cache_last_use < 0 ||
- dev->cache_last_use > 100000000) {
- /* Reset the cache usages */
- for (i = 1; i < dev->param.n_caches; i++)
- dev->cache[i].last_use = 0;
-
- dev->cache_last_use = 0;
- }
- dev->cache_last_use++;
- cache->last_use = dev->cache_last_use;
-
- if (is_write)
- cache->dirty = 1;
-}
-
-/* Invalidate a single cache page.
- * Do this when a whole page gets written,
- * ie the short cache for this page is no longer valid.
- */
-static void yaffs_invalidate_chunk_cache(struct yaffs_obj *object, int chunk_id)
-{
- struct yaffs_cache *cache;
-
- if (object->my_dev->param.n_caches > 0) {
- cache = yaffs_find_chunk_cache(object, chunk_id);
-
- if (cache)
- cache->object = NULL;
- }
-}
-
-/* Invalidate all the cache pages associated with this object
- * Do this whenever ther file is deleted or resized.
- */
-static void yaffs_invalidate_whole_cache(struct yaffs_obj *in)
-{
- u32 i;
- struct yaffs_dev *dev = in->my_dev;
-
- if (dev->param.n_caches > 0) {
- /* Invalidate it. */
- for (i = 0; i < dev->param.n_caches; i++) {
- if (dev->cache[i].object == in)
- dev->cache[i].object = NULL;
- }
- }
-}