From 9e94cd4fd1812bab45237f998b3c6fa1b24023fd Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 20 Jun 2006 15:01:12 +0200 Subject: [PATCH] [PATCH] splice: retrieve mapping after locking the page Otherwise we could be racing with truncate/mapping removal. Problem found/fixed by Nick Piggin , logic rewritten by me. Signed-off-by: Jens Axboe --- fs/splice.c | 46 +++++++++++++++++++++++++++++----------------- 1 file changed, 29 insertions(+), 17 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index a285fd746dc..05fd2787be9 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -55,31 +55,43 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { struct page *page = buf->page; - struct address_space *mapping = page_mapping(page); + struct address_space *mapping; lock_page(page); - WARN_ON(!PageUptodate(page)); + mapping = page_mapping(page); + if (mapping) { + WARN_ON(!PageUptodate(page)); - /* - * At least for ext2 with nobh option, we need to wait on writeback - * completing on this page, since we'll remove it from the pagecache. - * Otherwise truncate wont wait on the page, allowing the disk - * blocks to be reused by someone else before we actually wrote our - * data to them. fs corruption ensues. - */ - wait_on_page_writeback(page); + /* + * At least for ext2 with nobh option, we need to wait on + * writeback completing on this page, since we'll remove it + * from the pagecache. Otherwise truncate wont wait on the + * page, allowing the disk blocks to be reused by someone else + * before we actually wrote our data to them. fs corruption + * ensues. + */ + wait_on_page_writeback(page); - if (PagePrivate(page)) - try_to_release_page(page, mapping_gfp_mask(mapping)); + if (PagePrivate(page)) + try_to_release_page(page, mapping_gfp_mask(mapping)); - if (!remove_mapping(mapping, page)) { - unlock_page(page); - return 1; + /* + * If we succeeded in removing the mapping, set LRU flag + * and return good. + */ + if (remove_mapping(mapping, page)) { + buf->flags |= PIPE_BUF_FLAG_LRU; + return 0; + } } - buf->flags |= PIPE_BUF_FLAG_LRU; - return 0; + /* + * Raced with truncate or failed to remove page from current + * address space, unlock and return failure. + */ + unlock_page(page); + return 1; } static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe, -- 2.20.1