From patchwork Wed May 31 06:04:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 13261500 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 032BBC77B7C for ; Wed, 31 May 2023 06:05:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234332AbjEaGFf (ORCPT ); Wed, 31 May 2023 02:05:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59790 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234318AbjEaGFd (ORCPT ); Wed, 31 May 2023 02:05:33 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E37411D for ; Tue, 30 May 2023 23:05:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=BTF/fowlJXxRLAv+TuwF0phmMWOWDUXfJU6eqwdq8L4=; b=5BzPcQosJJaSaF3lNH+8gNcBXE hby5SdCTxWfZsEnfJKvAeKG/EqHSa4c4aAtRxyBHsTkTeSD1Njlucou8p96VSqIzeE8ayed3Rx/6a mlNwZTfiHQYah1BO/pEOu4Io2Olg+sWKF5jmmi6A7GdZoZH9DyzWc3XcsDd12YAvB6mo0q2xzv+hP NgTeryIQUSYjj+U8gKCHMd/pR/WX/eKiCPPONdOvweFRWIkbtJ+rk5g82EV5dLMX3ynROnfA3LET1 JK2M9cK0lO1GND1aeoHlzRNHvQzCcnE9E+VrJgurZ5Lel62/4dBQHSRrdiDrVIbk04+VFqx0QURVY XgDiH3jg==; Received: from [2001:4bb8:182:6d06:f5c3:53d7:b5aa:b6a7] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1q4Exe-00GF5q-1k; Wed, 31 May 2023 06:05:30 +0000 From: Christoph Hellwig To: Chris Mason , Josef Bacik , David Sterba Cc: linux-btrfs@vger.kernel.org Subject: [PATCH 07/16] btrfs: don't check PageError in __extent_writepage Date: Wed, 31 May 2023 08:04:56 +0200 Message-Id: <20230531060505.468704-8-hch@lst.de> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230531060505.468704-1-hch@lst.de> References: <20230531060505.468704-1-hch@lst.de> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org __extent_writepage currenly sets PageError whenever any error happens, and the also checks for PageError to decide if to call error handling. This leads to very unclear responsibility for cleaning up on errors. In the VM and generic writeback helpers the basic idea is that once I/O is fired off all error handling responsibility is delegated to the end I/O handler. But if that end I/O handler sets the PageError bit, and the submitter checks it, the bit could in some cases leak into the submission context for fast enough I/O. Fix this by simply not checking PageError and just using the local ret variable to check for submission errors. This also fundamentally solves the long problem documented in a comment in __extent_writepage by never leaking the error bit into the submission context. Signed-off-by: Christoph Hellwig --- fs/btrfs/extent_io.c | 33 +-------------------------------- 1 file changed, 1 insertion(+), 32 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 178e8230c28af9..33e5f0a31c21a7 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1557,38 +1557,7 @@ static int __extent_writepage(struct page *page, struct btrfs_bio_ctrl *bio_ctrl set_page_writeback(page); end_page_writeback(page); } - /* - * Here we used to have a check for PageError() and then set @ret and - * call end_extent_writepage(). - * - * But in fact setting @ret here will cause different error paths - * between subpage and regular sectorsize. - * - * For regular page size, we never submit current page, but only add - * current page to current bio. - * The bio submission can only happen in next page. - * Thus if we hit the PageError() branch, @ret is already set to - * non-zero value and will not get updated for regular sectorsize. - * - * But for subpage case, it's possible we submit part of current page, - * thus can get PageError() set by submitted bio of the same page, - * while our @ret is still 0. - * - * So here we unify the behavior and don't set @ret. - * Error can still be properly passed to higher layer as page will - * be set error, here we just don't handle the IO failure. - * - * NOTE: This is just a hotfix for subpage. - * The root fix will be properly ending ordered extent when we hit - * an error during writeback. - * - * But that needs a bigger refactoring, as we not only need to grab the - * submitted OE, but also need to know exactly at which bytenr we hit - * the error. - * Currently the full page based __extent_writepage_io() is not - * capable of that. - */ - if (PageError(page)) + if (ret) end_extent_writepage(page, ret, page_start, page_end); if (bio_ctrl->extent_locked) { struct writeback_control *wbc = bio_ctrl->wbc;