From patchwork Mon Jan 27 09:59:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nikolay Borisov X-Patchwork-Id: 11352297 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A7289159A for ; Mon, 27 Jan 2020 09:59:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FE08214AF for ; Mon, 27 Jan 2020 09:59:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726303AbgA0J7b (ORCPT ); Mon, 27 Jan 2020 04:59:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:53494 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726080AbgA0J7b (ORCPT ); Mon, 27 Jan 2020 04:59:31 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 0933CADE2; Mon, 27 Jan 2020 09:59:29 +0000 (UTC) From: Nikolay Borisov To: linux-btrfs@vger.kernel.org Cc: dsterba@suse.cz, Nikolay Borisov Subject: [PATCH] btrfs: Correctly handle empty trees in find_first_clear_extent_bit Date: Mon, 27 Jan 2020 11:59:26 +0200 Message-Id: <20200127095926.26069-1-nborisov@suse.com> X-Mailer: git-send-email 2.17.1 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Raviu reported that running his regular fs_trim segfaulted with the following backtrace: [ 237.525947] assertion failed: prev, in ../fs/btrfs/extent_io.c:1595 [ 237.525984] ------------[ cut here ]------------ [ 237.525985] kernel BUG at ../fs/btrfs/ctree.h:3117! [ 237.525992] invalid opcode: 0000 [#1] SMP PTI [ 237.525998] CPU: 4 PID: 4423 Comm: fstrim Tainted: G U OE 5.4.14-8-vanilla #1 [ 237.526001] Hardware name: ASUSTeK COMPUTER INC. [ 237.526044] RIP: 0010:assfail.constprop.58+0x18/0x1a [btrfs] [ 237.526079] Call Trace: [ 237.526120] find_first_clear_extent_bit+0x13d/0x150 [btrfs] [ 237.526148] btrfs_trim_fs+0x211/0x3f0 [btrfs] [ 237.526184] btrfs_ioctl_fitrim+0x103/0x170 [btrfs] [ 237.526219] btrfs_ioctl+0x129a/0x2ed0 [btrfs] [ 237.526227] ? filemap_map_pages+0x190/0x3d0 [ 237.526232] ? do_filp_open+0xaf/0x110 [ 237.526238] ? _copy_to_user+0x22/0x30 [ 237.526242] ? cp_new_stat+0x150/0x180 [ 237.526247] ? do_vfs_ioctl+0xa4/0x640 [ 237.526278] ? btrfs_ioctl_get_supported_features+0x30/0x30 [btrfs] [ 237.526283] do_vfs_ioctl+0xa4/0x640 [ 237.526288] ? __do_sys_newfstat+0x3c/0x60 [ 237.526292] ksys_ioctl+0x70/0x80 [ 237.526297] __x64_sys_ioctl+0x16/0x20 [ 237.526303] do_syscall_64+0x5a/0x1c0 [ 237.526310] entry_SYSCALL_64_after_hwframe+0x49/0xbe That was due to btrfs_fs_device::aloc_tree being empty. Initially I thought this wasn't possible and as a percaution have put the assert in find_first_clear_extent_bit. Turns out this is indeed possible and could happen when a file system with SINGLE data/metadata profile has a 2nd device added. Until balance is run or a new chunk is allocated on this device it will be completely empty. In this case find_first_clear_extent_bit should return the full range [0, -1ULL] and let the caller handle this i.e for trim the end will be capped at the size of actual device. Link: https://lore.kernel.org/linux-btrfs/izW2WNyvy1dEDweBICizKnd2KDwDiDyY2EYQr4YCwk7pkuIpthx-JRn65MPBde00ND6V0_Lh8mW0kZwzDiLDv25pUYWxkskWNJnVP0kgdMA=@protonmail.com/ Fixes: 45bfcfc168f8 ("btrfs: Implement find_first_clear_extent_bit") Signed-off-by: Nikolay Borisov --- David can you try and squeeze this into 5.5? It only leads to an assertion failure trigger (if assertion fs/btrfs/extent_io.c | 32 ++++++++++++++++++-------------- fs/btrfs/tests/extent-io-tests.c | 7 +++++++ 2 files changed, 25 insertions(+), 14 deletions(-) -- 2.17.1 diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 0351dbe64550..9bf7dffa22b1 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1593,21 +1593,25 @@ void find_first_clear_extent_bit(struct extent_io_tree *tree, u64 start, /* Find first extent with bits cleared */ while (1) { node = __etree_search(tree, start, &next, &prev, NULL, NULL); - if (!node) { + if (!node && !next && !prev) { + /* + * Tree is completely empty, send full range and let + * caller deal with it + */ + *start_ret = 0; + *end_ret = -1; + goto out; + } else if (!node && !next) { + /* + * We are past the last allocated chunk, set start at + * the end of the last extent. + */ + state = rb_entry(prev, struct extent_state, rb_node); + *start_ret = state->end + 1; + *end_ret = -1; + goto out; + } else if (!node) { node = next; - if (!node) { - /* - * We are past the last allocated chunk, - * set start at the end of the last extent. The - * device alloc tree should never be empty so - * prev is always set. - */ - ASSERT(prev); - state = rb_entry(prev, struct extent_state, rb_node); - *start_ret = state->end + 1; - *end_ret = -1; - goto out; - } } /* * At this point 'node' either contains 'start' or start is diff --git a/fs/btrfs/tests/extent-io-tests.c b/fs/btrfs/tests/extent-io-tests.c index 123d9a614357..2708c7e620cb 100644 --- a/fs/btrfs/tests/extent-io-tests.c +++ b/fs/btrfs/tests/extent-io-tests.c @@ -441,8 +441,15 @@ static int test_find_first_clear_extent_bit(void) int ret = -EINVAL; test_msg("running find_first_clear_extent_bit test"); + extent_io_tree_init(NULL, &tree, IO_TREE_SELFTEST, NULL); + /* Test correct handling of empty tree */ + find_first_clear_extent_bit(&tree, 0, &start, &end, CHUNK_TRIMMED); + if (start != 0 || end != -1) { + test_err("error getting a range from completely empty tree: start %llu end %llu", + start, end); + } /* * Set 1M-4M alloc/discard and 32M-64M thus leaving a hole between * 4M-32M