CacheFiles: Downgrade the requirements passed to the allocator

Downgrade the requirements passed to the allocator in the gfp flags parameter.
FS-Cache/CacheFiles can handle OOM conditions simply by aborting the attempt to
store an object or a page in the cache.

Signed-off-by: David Howells <[e-mail]>

fs/cachefiles/interface.c

···
 
 	_enter("{%s},%p,", cache->cache.identifier, cookie);
 
-	lookup_data = kmalloc(sizeof(*lookup_data), GFP_KERNEL);
+	lookup_data = kmalloc(sizeof(*lookup_data), cachefiles_gfp);
 	if (!lookup_data)
 		goto nomem_lookup_data;
 
 	/* create a new object record and a temporary leaf image */
-	object = kmem_cache_alloc(cachefiles_object_jar, GFP_KERNEL);
+	object = kmem_cache_alloc(cachefiles_object_jar, cachefiles_gfp);
 	if (!object)
 		goto nomem_object;
 
···
 	 * - stick the length on the front and leave space on the back for the
 	 *   encoder
 	 */
-	buffer = kmalloc((2 + 512) + 3, GFP_KERNEL);
+	buffer = kmalloc((2 + 512) + 3, cachefiles_gfp);
 	if (!buffer)
 		goto nomem_buffer;
 
···
 		return;
 	}
 
-	auxdata = kmalloc(2 + 512 + 3, GFP_KERNEL);
+	auxdata = kmalloc(2 + 512 + 3, cachefiles_gfp);
 	if (!auxdata) {
 		_leave(" [nomem]");
 		return;

fs/cachefiles/internal.h

···
 #define CACHEFILES_DEBUG_KLEAVE	2
 #define CACHEFILES_DEBUG_KDEBUG	4
 
+#define cachefiles_gfp (__GFP_WAIT | __GFP_NORETRY | __GFP_NOMEMALLOC)
+
 /*
  * node records
  */

fs/cachefiles/key.c

···
 
 	_debug("max: %d", max);
 
-	key = kmalloc(max, GFP_KERNEL);
+	key = kmalloc(max, cachefiles_gfp);
 	if (!key)
 		return NULL;
 

fs/cachefiles/rdwr.c

···
 	_debug("read back %p{%lu,%d}",
 	       netpage, netpage->index, page_count(netpage));
 
-	monitor = kzalloc(sizeof(*monitor), GFP_KERNEL);
+	monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
 	if (!monitor)
 		goto nomem;
 
···
 			goto backing_page_already_present;
 
 		if (!newpage) {
-			newpage = page_cache_alloc_cold(bmapping);
+			newpage = __page_cache_alloc(cachefiles_gfp |
+						     __GFP_COLD);
 			if (!newpage)
 				goto nomem_monitor;
 		}
 
 		ret = add_to_page_cache(newpage, bmapping,
-					netpage->index, GFP_KERNEL);
+					netpage->index, cachefiles_gfp);
 		if (ret == 0)
 			goto installed_new_backing_page;
 		if (ret != -EEXIST)
···
 		       netpage, netpage->index, page_count(netpage));
 
 		if (!monitor) {
-			monitor = kzalloc(sizeof(*monitor), GFP_KERNEL);
+			monitor = kzalloc(sizeof(*monitor), cachefiles_gfp);
 			if (!monitor)
 				goto nomem;
 
···
 				goto backing_page_already_present;
 
 			if (!newpage) {
-				newpage = page_cache_alloc_cold(bmapping);
+				newpage = __page_cache_alloc(cachefiles_gfp |
+							     __GFP_COLD);
 				if (!newpage)
 					goto nomem;
 			}
 
 			ret = add_to_page_cache(newpage, bmapping,
-						netpage->index, GFP_KERNEL);
+						netpage->index, cachefiles_gfp);
 			if (ret == 0)
 				goto installed_new_backing_page;
 			if (ret != -EEXIST)
···
 		_debug("- monitor add");
 
 		ret = add_to_page_cache(netpage, op->mapping, netpage->index,
-					GFP_KERNEL);
+					cachefiles_gfp);
 		if (ret < 0) {
 			if (ret == -EEXIST) {
 				page_cache_release(netpage);
···
 		_debug("- uptodate");
 
 		ret = add_to_page_cache(netpage, op->mapping, netpage->index,
-					GFP_KERNEL);
+					cachefiles_gfp);
 		if (ret < 0) {
 			if (ret == -EEXIST) {
 				page_cache_release(netpage);

fs/cachefiles/xattr.c

···
 	ASSERT(dentry);
 	ASSERT(dentry->d_inode);
 
-	auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
+	auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, cachefiles_gfp);
 	if (!auxbuf) {
 		_leave(" = -ENOMEM");
 		return -ENOMEM;

fs/fscache/page.c

···
 
 	fscache_stat(&fscache_n_stores);
 
-	op = kzalloc(sizeof(*op), GFP_NOIO);
+	op = kzalloc(sizeof(*op), GFP_NOIO | __GFP_NOMEMALLOC | __GFP_NORETRY);
 	if (!op)
 		goto nomem;