ext4: don't allow ext4_free_blocks() to fail due to ENOMEM

The filesystem should not be marked inconsistent if ext4_free_blocks() is not able to allocate memory. Unfortunately some callers (most notably ext4_truncate) don't have a way to reflect an error back up to the VFS. And even if we did, most userspace applications won't deal with most system calls returning ENOMEM anyway. Reported-by: Nagachandra P <[email protected]> Signed-off-by: "Theodore Ts'o" <[email protected]> Cc: [email protected]
ambv · Jul 13, 2013 · e7676a7 · e7676a7
1 parent bdafe42
commit e7676a7
Showing 1 changed file with 8 additions and 3 deletions.
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
@@ -4740,11 +4740,16 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
 		 * blocks being freed are metadata. these blocks shouldn't
 		 * be used until this transaction is committed
 		 */
+	retry:
 		new_entry = kmem_cache_alloc(ext4_free_data_cachep, GFP_NOFS);
 		if (!new_entry) {
-			ext4_mb_unload_buddy(&e4b);
-			err = -ENOMEM;
-			goto error_return;
+			/*
+			 * We use a retry loop because
+			 * ext4_free_blocks() is not allowed to fail.
+			 */
+			cond_resched();
+			congestion_wait(BLK_RW_ASYNC, HZ/50);
+			goto retry;
 		}
 		new_entry->efd_start_cluster = bit;
 		new_entry->efd_group = block_group;