From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8CBD0C43331 for ; Tue, 2 Mar 2021 03:08:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5582D61606 for ; Tue, 2 Mar 2021 03:08:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380380AbhCBBut (ORCPT ); Mon, 1 Mar 2021 20:50:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:48622 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241704AbhCAT2r (ORCPT ); Mon, 1 Mar 2021 14:28:47 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 40EA364D99; Mon, 1 Mar 2021 17:47:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614620841; bh=Q+bTeE3XrDdXjs5gx2nhKReqJz1aB39R9NdGzohYdo4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qci1FR8XrQMPOcdtIHqypn/srTPAwJ2SKl3zGP5olr0rVQ8jjHFTmS5bUQbaK9//h 0XYvjjrVDn6pk5eqn8Je/bUWRTm5f3JNzSiBiEBjmugZ0EDlcVv+sTH+lenmp+D+PR RYZM3vPP6Sx4oc73aEfQEhPe7jTXLS83Ps/erbAI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Filipe Manana , Qu Wenruo , David Sterba , Sasha Levin Subject: [PATCH 5.11 269/775] btrfs: fix double accounting of ordered extent for subpage case in btrfs_invalidapge Date: Mon, 1 Mar 2021 17:07:17 +0100 Message-Id: <20210301161214.923731286@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161201.679371205@linuxfoundation.org> References: <20210301161201.679371205@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Qu Wenruo [ Upstream commit 951c80f83d61bd4b21794c8aba829c3c1a45c2d0 ] Commit dbfdb6d1b369 ("Btrfs: Search for all ordered extents that could span across a page") make btrfs_invalidapage() to search all ordered extents. The offending code looks like this: again: start = page_start; ordered = btrfs_lookup_ordered_range(inode, start, page_end - start + 1); if (ordred) { end = min(page_end, ordered->file_offset + ordered->num_bytes - 1); /* Do the cleanup */ start = end + 1; if (start < page_end) goto again; } The behavior is indeed necessary for the incoming subpage support, but when it iterates through all the ordered extents, it also resets the search range @start. This means, for the following cases, we can double account the ordered extents, causing its bytes_left underflow: Page offset 0 16K 32K |<--- OE 1 --->|<--- OE 2 ---->| As the first iteration will find ordered extent (OE) 1, which doesn't cover the full page, thus after cleanup code, we need to retry again. But again label will reset start to page_start, and we got OE 1 again, which causes double accounting on OE 1, and cause OE 1's byte_left to underflow. This problem can only happen for subpage case, as for regular sectorsize == PAGE_SIZE case, we will always find a OE ends at or after page end, thus no way to trigger the problem. Move the again label after start = page_start. There will be more comprehensive rework to convert the open coded loop to a proper while loop for subpage support. Fixes: dbfdb6d1b369 ("Btrfs: Search for all ordered extents that could span across a page") Reviewed-by: Filipe Manana Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/inode.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index a8e0a6b038d3e..ad34c5a09befc 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8186,8 +8186,9 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset, if (!inode_evicting) lock_extent_bits(tree, page_start, page_end, &cached_state); -again: + start = page_start; +again: ordered = btrfs_lookup_ordered_range(inode, start, page_end - start + 1); if (ordered) { found_ordered = true; -- 2.27.0