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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 83597C2BA83 for ; Fri, 14 Feb 2020 16:04:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 582D02067D for ; Fri, 14 Feb 2020 16:04:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581696254; bh=06HiugEeIyT64UGKH2uwweFX+Jujms0kwmNzncT3wpo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=BKBAgsxIhOYWtzaN61apMoZdHpDSI65j5h0l1Qmu3J0ASEnZwvSYcUE+TXvJRUq4R s6Qezo1PRcWU7MbHPGpqNJVAUgXk6roYb/cAfztRv4mSo5Lxp56Gp3u6eeF+ZTY1OC RJn8PXzRJQbpUTiaz+VJOEccfgv+HJvSkHoJ4oJ0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389866AbgBNQEN (ORCPT ); Fri, 14 Feb 2020 11:04:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:52098 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389391AbgBNQEM (ORCPT ); Fri, 14 Feb 2020 11:04:12 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1184324654; Fri, 14 Feb 2020 16:04:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581696251; bh=06HiugEeIyT64UGKH2uwweFX+Jujms0kwmNzncT3wpo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XQhTmyH0SF1M8O6xLCislbbPQpPmJWGcIZRbgN3t11Qj+zzC9XWirT1bHhxKt36WM sU9jljALkfefsoJEWOSXvW/Lj0rOeA2ZK6Jf5YkNCXW8hM45uchSSFJ6rDmNCVbtrh XK0EQ5j1IFhxaGeNrxhWR3BHJGx4LRMtVIh0B9N0= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Chris Mason , Josef Bacik , David Sterba , Sasha Levin , linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 5.4 107/459] Btrfs: keep pages dirty when using btrfs_writepage_fixup_worker Date: Fri, 14 Feb 2020 10:55:57 -0500 Message-Id: <20200214160149.11681-107-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200214160149.11681-1-sashal@kernel.org> References: <20200214160149.11681-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Chris Mason [ Upstream commit 25f3c5021985e885292980d04a1423fd83c967bb ] For COW, btrfs expects pages dirty pages to have been through a few setup steps. This includes reserving space for the new block allocations and marking the range in the state tree for delayed allocation. A few places outside btrfs will dirty pages directly, especially when unmapping mmap'd pages. In order for these to properly go through COW, we run them through a fixup worker to wait for stable pages, and do the delalloc prep. 87826df0ec36 added a window where the dirty pages were cleaned, but pending more action from the fixup worker. We clear_page_dirty_for_io() before we call into writepage, so the page is no longer dirty. The commit changed it so now we leave the page clean between unlocking it here and the fixup worker starting at some point in the future. During this window, page migration can jump in and relocate the page. Once our fixup work actually starts, it finds page->mapping is NULL and we end up freeing the page without ever writing it. This leads to crc errors and other exciting problems, since it screws up the whole statemachine for waiting for ordered extents. The fix here is to keep the page dirty while we're waiting for the fixup worker to get to work. This is accomplished by returning -EAGAIN from btrfs_writepage_cow_fixup if we queued the page up for fixup, which will cause the writepage function to redirty the page. Because we now expect the page to be dirty once it gets to the fixup worker we must adjust the error cases to call clear_page_dirty_for_io() on the page. That is the bulk of the patch, but it is not the fix, the fix is the -EAGAIN from btrfs_writepage_cow_fixup. We cannot separate these two changes out because the error conditions change with the new expectations. Signed-off-by: Chris Mason Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/inode.c | 61 ++++++++++++++++++++++++++++++++++-------------- 1 file changed, 44 insertions(+), 17 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 6f0568fb58997..1b4ab02be9243 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -2181,17 +2181,27 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work) struct inode *inode; u64 page_start; u64 page_end; - int ret; + int ret = 0; fixup = container_of(work, struct btrfs_writepage_fixup, work); page = fixup->page; again: lock_page(page); - if (!page->mapping || !PageDirty(page) || !PageChecked(page)) { - ClearPageChecked(page); + + /* + * Before we queued this fixup, we took a reference on the page. + * page->mapping may go NULL, but it shouldn't be moved to a different + * address space. + */ + if (!page->mapping || !PageDirty(page) || !PageChecked(page)) goto out_page; - } + /* + * We keep the PageChecked() bit set until we're done with the + * btrfs_start_ordered_extent() dance that we do below. That drops and + * retakes the page lock, so we don't want new fixup workers queued for + * this page during the churn. + */ inode = page->mapping->host; page_start = page_offset(page); page_end = page_offset(page) + PAGE_SIZE - 1; @@ -2216,24 +2226,22 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work) ret = btrfs_delalloc_reserve_space(inode, &data_reserved, page_start, PAGE_SIZE); - if (ret) { - mapping_set_error(page->mapping, ret); - end_extent_writepage(page, ret, page_start, page_end); - ClearPageChecked(page); + if (ret) goto out; - } ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0, &cached_state); - if (ret) { - mapping_set_error(page->mapping, ret); - end_extent_writepage(page, ret, page_start, page_end); - ClearPageChecked(page); + if (ret) goto out_reserved; - } - ClearPageChecked(page); - set_page_dirty(page); + /* + * Everything went as planned, we're now the owner of a dirty page with + * delayed allocation bits set and space reserved for our COW + * destination. + * + * The page was dirty when we started, nothing should have cleaned it. + */ + BUG_ON(!PageDirty(page)); out_reserved: btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE); if (ret) @@ -2243,6 +2251,17 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work) unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start, page_end, &cached_state); out_page: + if (ret) { + /* + * We hit ENOSPC or other errors. Update the mapping and page + * to reflect the errors and clean the page. + */ + mapping_set_error(page->mapping, ret); + end_extent_writepage(page, ret, page_start, page_end); + clear_page_dirty_for_io(page); + SetPageError(page); + } + ClearPageChecked(page); unlock_page(page); put_page(page); kfree(fixup); @@ -2270,6 +2289,13 @@ int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end) if (TestClearPagePrivate2(page)) return 0; + /* + * PageChecked is set below when we create a fixup worker for this page, + * don't try to create another one if we're already PageChecked() + * + * The extent_io writepage code will redirty the page if we send back + * EAGAIN. + */ if (PageChecked(page)) return -EAGAIN; @@ -2282,7 +2308,8 @@ int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end) btrfs_init_work(&fixup->work, btrfs_writepage_fixup_worker, NULL, NULL); fixup->page = page; btrfs_queue_work(fs_info->fixup_workers, &fixup->work); - return -EBUSY; + + return -EAGAIN; } static int insert_reserved_file_extent(struct btrfs_trans_handle *trans, -- 2.20.1