X-Git-Url: http://aleph1.co.uk/gitweb/?a=blobdiff_plain;ds=sidebyside;f=yaffs_cache.c;fp=yaffs_cache.c;h=27f54e2c602b1abab1337dd569278f2664261c7a;hb=b21bef3bd5ef583feed45f0500a1058cbaa47136;hp=0000000000000000000000000000000000000000;hpb=edbbbac4c481931fa84174b861b6cbbca93fb13d;p=yaffs2.git

diff --git a/yaffs_cache.c b/yaffs_cache.c
new file mode 100644
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--- /dev/null
+++ b/yaffs_cache.c
@@ -0,0 +1,298 @@
+/*
+ * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
+ *
+ * Copyright (C) 2002-2018 Aleph One Ltd.
+ *
+ * Created by Charles Manning <charles@aleph1.co.uk>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "yaffs_cache.h"
+
+/*------------------------ 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.
+ */
+
+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;
+}
+
+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;
+}
+
+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;
+}
+
+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 */
+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 */
+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.
+ */
+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.
+ */
+void yaffs_invalidate_file_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;
+		}
+	}
+}
+
+
+int yaffs_cache_init(struct yaffs_dev *dev)
+{
+	int init_failed;
+
+	if (dev->param.n_caches > 0) {
+		u32 i;
+		void *buf;
+		u32 cache_bytes =
+		    dev->param.n_caches * sizeof(struct yaffs_cache);
+
+		if (dev->param.n_caches > YAFFS_MAX_SHORT_OP_CACHES)
+			dev->param.n_caches = YAFFS_MAX_SHORT_OP_CACHES;
+
+		dev->cache = kmalloc(cache_bytes, GFP_NOFS);
+
+		buf = (u8 *) dev->cache;
+
+		if (dev->cache)
+			memset(dev->cache, 0, cache_bytes);
+
+		for (i = 0; i < dev->param.n_caches && buf; i++) {
+			dev->cache[i].object = NULL;
+			dev->cache[i].last_use = 0;
+			dev->cache[i].dirty = 0;
+			dev->cache[i].data = buf =
+			    kmalloc(dev->param.total_bytes_per_chunk, GFP_NOFS);
+		}
+		if (!buf)
+			init_failed = 1;
+
+		dev->cache_last_use = 0;
+	}
+
+	return init_failed ? -1 : 0;
+}
+
+void yaffs_cache_deinit(struct yaffs_dev *dev)
+{
+
+	if (dev->param.n_caches > 0 && dev->cache) {
+		u32 i;
+
+		for (i = 0; i < dev->param.n_caches; i++) {
+			kfree(dev->cache[i].data);
+			dev->cache[i].data = NULL;
+		}
+
+		kfree(dev->cache);
+		dev->cache = NULL;
+	}
+}