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 16361C433ED for ; Fri, 21 May 2021 06:43:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F07B4611AB for ; Fri, 21 May 2021 06:43:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233963AbhEUGoX (ORCPT ); Fri, 21 May 2021 02:44:23 -0400 Received: from mx2.suse.de ([195.135.220.15]:58788 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234763AbhEUGny (ORCPT ); Fri, 21 May 2021 02:43:54 -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=1621579276; 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=j6wwqZ2NHQ98V9BxCk2fJD9t3QEV7jgtGjgySMsAl/o=; b=UJv9cl1r/+c7NHy+G9VBOs++Ylyb09tw6klKqSgVb/YPDUm2ccTSgD/o2TGRqqLmrPLEiP c5TBcsVKknGP2IhfsapQLOHPvVnMfMbSCLkEaduicLLwUJ/CvjSdpQT5avmQS+mpI7t8kV 7NvVfvtf1hwpIhrYs6+LkVaKr0eIF6Q= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AC1C6AD1B for ; Fri, 21 May 2021 06:41:16 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v3 12/31] btrfs: prevent extent_clear_unlock_delalloc() to unlock page not locked by __process_pages_contig() Date: Fri, 21 May 2021 14:40:31 +0800 Message-Id: <20210521064050.191164-13-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 In cow_file_range(), after we have succeeded creating an inline extent, we unlock the page with extent_clear_unlock_delalloc() by passing locked_page == NULL. For sectorsize == PAGE_SIZE case, this is just making the page lock and unlock harder to grab. But for incoming subpage case, it can be a big problem. For incoming subpage case, page locking have two entrace: - __process_pages_contig() In that case, we know exactly the range we want to lock (which only requires sector alignment). To handle the subpage requirement, we introduce btrfs_subpage::writers to page::private, and will update it in __process_pages_contig(). - Other directly lock/unlock_page() call sites Those won't touch btrfs_subpage::writers at all. This means, page locked by __process_pages_contig() can only be unlocked by __process_pages_contig(). Thankfully we already have the existing infrastructure in the form of @locked_page in various call sites. Unfortunately, extent_clear_unlock_delalloc() in cow_file_range() after creating an inline extent is the exception. It intentionally call extent_clear_unlock_delalloc() with locked_page == NULL, to also unlock current page (and clear its dirty/writeback bits). To co-operate with incoming subpage modifications, and make the page lock/unlock pair easier to understand, this patch will still call extent_clear_unlock_delalloc() with locked_page, and only unlock the page in __extent_writepage(). Signed-off-by: Qu Wenruo --- fs/btrfs/inode.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index a18881c7c916..119834aa3587 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1091,7 +1091,8 @@ static noinline int cow_file_range(struct btrfs_inode *inode, * our outstanding extent for clearing delalloc for this * range. */ - extent_clear_unlock_delalloc(inode, start, end, NULL, + extent_clear_unlock_delalloc(inode, start, end, + locked_page, EXTENT_LOCKED | EXTENT_DELALLOC | EXTENT_DELALLOC_NEW | EXTENT_DEFRAG | EXTENT_DO_ACCOUNTING, PAGE_UNLOCK | @@ -1099,6 +1100,19 @@ static noinline int cow_file_range(struct btrfs_inode *inode, *nr_written = *nr_written + (end - start + PAGE_SIZE) / PAGE_SIZE; *page_started = 1; + /* + * locked_page is locked by the caller of + * writepage_delalloc(), not locked by + * __process_pages_contig(). + * + * We can't let __process_pages_contig() to unlock it, + * as it doesn't have any subpage::writers recorded. + * + * Here we manually unlock the page, since the caller + * can't use page_started to determine if it's an + * inline extent or a compressed extent. + */ + unlock_page(locked_page); goto out; } else if (ret < 0) { goto out_unlock; -- 2.31.1