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=-18.7 required=3.0 tests=BAYES_00,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=ham 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 0305CC433B4 for ; Fri, 21 May 2021 06:43:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DFB646135C for ; Fri, 21 May 2021 06:43:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233698AbhEUGoz (ORCPT ); Fri, 21 May 2021 02:44:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:59010 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233651AbhEUGoT (ORCPT ); Fri, 21 May 2021 02:44:19 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1621579288; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UFDZa95E5N4vSGBOtLPmqCESeN/Vw++PjBgEYXF2Jms=; b=seP1kXam/MAR7KCna2IISsaNt775Dm1+c7Xv87y2qsAbrcF5SXeQvgkNQygw3j1HgKVxEZ sKeo0wJKg17yzMQeXp7Dl3nZZJ7oAAvZH+xpk6RQeJ99xSAGE6Qli/oXnG7iVWWgedFoM5 jSKljhLOLMcRqyZi5lDliBwJn/Ld9IA= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7D723AE4B for ; Fri, 21 May 2021 06:41:28 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v3 19/31] btrfs: don't clear page extent mapped if we're not invalidating the full page Date: Fri, 21 May 2021 14:40:38 +0800 Message-Id: <20210521064050.191164-20-wqu@suse.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210521064050.191164-1-wqu@suse.com> References: <20210521064050.191164-1-wqu@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org [BUG] With current btrfs subpage rw support, the following script can lead to fs hang: mkfs.btrfs -f -s 4k $dev mount $dev -o nospace_cache $mnt fsstress -w -n 100 -p 1 -s 1608140256 -v -d $mnt The fs will hang at btrfs_start_ordered_extent(). [CAUSE] In above test case, btrfs_invalidate() will be called with the following parameters: offset = 0 length = 53248 page dirty = 1 subpage dirty bitmap = 0x2000 Since @offset is 0, btrfs_invalidate() will try to invalidate the full page, and finally call clear_page_extent_mapped() which will detach btrfs subpage structure from the page. And since the page no longer has btrfs subpage structure, the subpage dirty bitmap will be cleared, preventing the dirty range from written back, thus no way to wake up the ordered extent. [FIX] Just follow other fses, only to invalidate the page if the range covers the full page. There are cases like truncate_setsize() which can call btrfs_invalidatepage() with offset == 0 and length != 0 for the last page of an inode. Although the old code will still try to invalidate the full page, we are still safe to just wait for ordered extent to finish. So it shouldn't cause extra problems. Signed-off-by: Qu Wenruo --- fs/btrfs/inode.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 39049a614b7c..f82055ba09c8 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8351,7 +8351,19 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset, */ wait_on_page_writeback(page); - if (offset) { + /* + * For subpage case, we have call sites like + * btrfs_punch_hole_lock_range() which passes range not aligned to + * sectorsize. + * If the range doesn't cover the full page, we don't need to and + * shouldn't clear page extent mapped, as page->private can still + * record subpage dirty bits for other part of the range. + * + * For cases where can invalidate the full even the range doesn't + * cover the full page, like invalidating the last page, we're + * still safe to wait for ordered extent to finish. + */ + if (!(offset == 0 && length == PAGE_SIZE)) { btrfs_releasepage(page, GFP_NOFS); return; } -- 2.31.1