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,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 F018BC47094 for ; Mon, 31 May 2021 08:51:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D65A66108D for ; Mon, 31 May 2021 08:51:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231161AbhEaIxh (ORCPT ); Mon, 31 May 2021 04:53:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:41160 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231129AbhEaIxY (ORCPT ); Mon, 31 May 2021 04:53:24 -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=1622451104; 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=wI1ILNHcrHD75g0UQfM3LXMP8WIpfno/tD2x8n8V6IA=; b=KdkDE5dPsz+bwl6uj9P+Ft9jQka6xyAL+fJMC3GXyIh2u4Uxxcuze46EetnQLdHUD/JyTc /0ICbgI46IC3HbrqqW7j1j5FHwY3lgdypJSzLMwysqR3etfZ+1AeqCk2n0MdxNQZMu0794 Zy+W8GYcxsPMIgtXfHIGcMzI9henKyc= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B7711B2E9 for ; Mon, 31 May 2021 08:51:44 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v4 19/30] btrfs: don't clear page extent mapped if we're not invalidating the full page Date: Mon, 31 May 2021 16:50:55 +0800 Message-Id: <20210531085106.259490-20-wqu@suse.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210531085106.259490-1-wqu@suse.com> References: <20210531085106.259490-1-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 e756423a7a70..c3d5abf3df5f 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8363,7 +8363,19 @@ 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