Btrfs: don't leak pages and memory on compressed write error

In inode.c:submit_compressed_extents(), if we fail before calling
btrfs_submit_compressed_write(), or when that function fails, we
were freeing the async_extent structure without releasing its pages
and freeing the pages array.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/inode.c

@@ -633,6 +633,22 @@ static noinline int compress_file_range(struct inode *inode,
 	goto out;
 }
 
+static void free_async_extent_pages(struct async_extent *async_extent)
+{
+	int i;
+
+	if (!async_extent->pages)
+		return;
+
+	for (i = 0; i < async_extent->nr_pages; i++) {
+		WARN_ON(async_extent->pages[i]->mapping);
+		page_cache_release(async_extent->pages[i]);
+	}
+	kfree(async_extent->pages);
+	async_extent->nr_pages = 0;
+	async_extent->pages = NULL;
+}
+
 /*
  * phase two of compressed writeback.  This is the ordered portion
  * of the code, which only gets called in the order the work was
@@ -709,15 +725,7 @@ static noinline int submit_compressed_extents(struct inode *inode,
 					   async_extent->compressed_size,
 					   0, alloc_hint, &ins, 1, 1);
 		if (ret) {
-			int i;
-
-			for (i = 0; i < async_extent->nr_pages; i++) {
-				WARN_ON(async_extent->pages[i]->mapping);
-				page_cache_release(async_extent->pages[i]);
-			}
-			kfree(async_extent->pages);
-			async_extent->nr_pages = 0;
-			async_extent->pages = NULL;
+			free_async_extent_pages(async_extent);
 
 			if (ret == -ENOSPC) {
 				unlock_extent(io_tree, async_extent->start,
@@ -827,6 +835,7 @@ static noinline int submit_compressed_extents(struct inode *inode,
 			extent_clear_unlock_delalloc(inode, start, end, NULL, 0,
 						     PAGE_END_WRITEBACK |
 						     PAGE_SET_ERROR);
+			free_async_extent_pages(async_extent);
 		}
 		alloc_hint = ins.objectid + ins.offset;
 		kfree(async_extent);
@@ -848,6 +857,7 @@ static noinline int submit_compressed_extents(struct inode *inode,
 				     PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
 				     PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK |
 				     PAGE_SET_ERROR);
+	free_async_extent_pages(async_extent);
 	kfree(async_extent);
 	goto again;
 }