Squashfs: refactor page_actor

This patch essentially does 3 things:
  1/ Always use an array of page to store the data instead of a mix of
     buffers and pages.
  2/ It is now possible to have 'holes' in a page actor, i.e. NULL
     pages in the array.
     When reading a block (default 128K), squashfs tries to grab all
     the pages covering this block. If a single page is up-to-date or
     locked, it falls back to using an intermediate buffer to do the
     read and then copy the pages in the actor. Allowing holes in the
     page actor remove the need for this intermediate buffer.
  3/ Refactor the wrappers to share code that deals with page actors.

Signed-off-by: Adrien Schildknecht <adriens@google.com>
Change-Id: I98128bed5d518cf31b67e788a85b275e9a323bec

1 files changed, 29 insertions, 44 deletions

diff --git a/fs/squashfs/cache.c b/fs/squashfs/cache.c
index 1cb70a0b2168..6785d086ab38 100644
--- a/fs/squashfs/cache.c
+++ b/fs/squashfs/cache.c
@@ -209,17 +209,14 @@ void squashfs_cache_put(struct squashfs_cache_entry *entry)
  */
 void squashfs_cache_delete(struct squashfs_cache *cache)
 {
-	int i, j;
+	int i;
 
 	if (cache == NULL)
 		return;
 
 	for (i = 0; i < cache->entries; i++) {
-		if (cache->entry[i].data) {
-			for (j = 0; j < cache->pages; j++)
-				kfree(cache->entry[i].data[j]);
-			kfree(cache->entry[i].data);
-		}
+		if (cache->entry[i].page)
+			free_page_array(cache->entry[i].page, cache->pages);
 		kfree(cache->entry[i].actor);
 	}
 
@@ -236,7 +233,7 @@ void squashfs_cache_delete(struct squashfs_cache *cache)
 struct squashfs_cache *squashfs_cache_init(char *name, int entries,
 	int block_size)
 {
-	int i, j;
+	int i;
 	struct squashfs_cache *cache = kzalloc(sizeof(*cache), GFP_KERNEL);
 
 	if (cache == NULL) {
@@ -268,22 +265,13 @@ struct squashfs_cache *squashfs_cache_init(char *name, int entries,
 		init_waitqueue_head(&cache->entry[i].wait_queue);
 		entry->cache = cache;
 		entry->block = SQUASHFS_INVALID_BLK;
-		entry->data = kcalloc(cache->pages, sizeof(void *), GFP_KERNEL);
-		if (entry->data == NULL) {
+		entry->page = alloc_page_array(cache->pages, GFP_KERNEL);
+		if (!entry->page) {
 			ERROR("Failed to allocate %s cache entry\n", name);
 			goto cleanup;
 		}
-
-		for (j = 0; j < cache->pages; j++) {
-			entry->data[j] = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);
-			if (entry->data[j] == NULL) {
-				ERROR("Failed to allocate %s buffer\n", name);
-				goto cleanup;
-			}
-		}
-
-		entry->actor = squashfs_page_actor_init(entry->data,
-						cache->pages, 0);
+		entry->actor = squashfs_page_actor_init(entry->page,
+			cache->pages, 0, NULL);
 		if (entry->actor == NULL) {
 			ERROR("Failed to allocate %s cache entry\n", name);
 			goto cleanup;
@@ -314,18 +302,20 @@ int squashfs_copy_data(void *buffer, struct squashfs_cache_entry *entry,
 		return min(length, entry->length - offset);
 
 	while (offset < entry->length) {
-		void *buff = entry->data[offset / PAGE_CACHE_SIZE]
-				+ (offset % PAGE_CACHE_SIZE);
+		void *buff = kmap_atomic(entry->page[offset / PAGE_CACHE_SIZE])
+			     + (offset % PAGE_CACHE_SIZE);
 		int bytes = min_t(int, entry->length - offset,
 				PAGE_CACHE_SIZE - (offset % PAGE_CACHE_SIZE));
 
 		if (bytes >= remaining) {
 			memcpy(buffer, buff, remaining);
+			kunmap_atomic(buff);
 			remaining = 0;
 			break;
 		}
 
 		memcpy(buffer, buff, bytes);
+		kunmap_atomic(buff);
 		buffer += bytes;
 		remaining -= bytes;
 		offset += bytes;
@@ -416,43 +406,38 @@ struct squashfs_cache_entry *squashfs_get_datablock(struct super_block *sb,
 void *squashfs_read_table(struct super_block *sb, u64 block, int length)
 {
 	int pages = (length + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-	int i, res;
-	void *table, *buffer, **data;
+	struct page **page;
+	void *buff;
+	int res;
 	struct squashfs_page_actor *actor;
 
-	table = buffer = kmalloc(length, GFP_KERNEL);
-	if (table == NULL)
+	page = alloc_page_array(pages, GFP_KERNEL);
+	if (!page)
 		return ERR_PTR(-ENOMEM);
 
-	data = kcalloc(pages, sizeof(void *), GFP_KERNEL);
-	if (data == NULL) {
-		res = -ENOMEM;
-		goto failed;
-	}
-
-	actor = squashfs_page_actor_init(data, pages, length);
+	actor = squashfs_page_actor_init(page, pages, length, NULL);
 	if (actor == NULL) {
 		res = -ENOMEM;
-		goto failed2;
+		goto failed;
 	}
 
-	for (i = 0; i < pages; i++, buffer += PAGE_CACHE_SIZE)
-		data[i] = buffer;
-
 	res = squashfs_read_data(sb, block, length |
 		SQUASHFS_COMPRESSED_BIT_BLOCK, NULL, actor);
 
-	kfree(data);
-	kfree(actor);
-
 	if (res < 0)
-		goto failed;
+		goto failed2;
 
-	return table;
+	buff = kmalloc(length, GFP_KERNEL);
+	if (!buff)
+		goto failed2;
+	squashfs_actor_to_buf(actor, buff, length);
+	squashfs_page_actor_free(actor, 0);
+	free_page_array(page, pages);
+	return buff;
 
 failed2:
-	kfree(data);
+	squashfs_page_actor_free(actor, 0);
 failed:
-	kfree(table);
+	free_page_array(page, pages);
 	return ERR_PTR(res);
 }