From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:53492 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752039AbdLVHv0 (ORCPT ); Fri, 22 Dec 2017 02:51:26 -0500 Subject: Re: [PATCH 04/10] Btrfs: extent map selftest: buffered write vs dio read To: Liu Bo , linux-btrfs@vger.kernel.org References: <20171221224256.18196-1-bo.li.liu@oracle.com> <20171221224256.18196-5-bo.li.liu@oracle.com> From: Nikolay Borisov Message-ID: <703352d3-8b80-1df1-e2ad-192e7e738a8d@suse.com> Date: Fri, 22 Dec 2017 09:51:24 +0200 MIME-Version: 1.0 In-Reply-To: <20171221224256.18196-5-bo.li.liu@oracle.com> Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 22.12.2017 00:42, Liu Bo wrote: > This test case simulates the racy situation of buffered write vs dio > read, and see if btrfs_get_extent() would return -EEXIST. Isn't mixing dio/buffered IO on the same file (range?) considered dangerous in any case? > > Signed-off-by: Liu Bo > --- > fs/btrfs/tests/extent-map-tests.c | 73 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 73 insertions(+) > > diff --git a/fs/btrfs/tests/extent-map-tests.c b/fs/btrfs/tests/extent-map-tests.c > index 0407396..2adf55f 100644 > --- a/fs/btrfs/tests/extent-map-tests.c > +++ b/fs/btrfs/tests/extent-map-tests.c > @@ -181,6 +181,78 @@ static void test_case_2(struct extent_map_tree *em_tree) > free_extent_map_tree(em_tree); > } > > +static void __test_case_3(struct extent_map_tree *em_tree, u64 start) > +{ > + struct extent_map *em; > + u64 len = SZ_4K; > + int ret; > + > + em = alloc_extent_map(); > + if (!em) > + /* Skip this test on error. */ > + return; > + > + /* Add [4K, 8K) */ > + em->start = SZ_4K; > + em->len = SZ_4K; > + em->block_start = SZ_4K; > + em->block_len = SZ_4K; > + ret = add_extent_mapping(em_tree, em, 0); > + ASSERT(ret == 0); > + free_extent_map(em); > + > + em = alloc_extent_map(); > + if (!em) > + goto out; > + > + /* Add [0, 16K) */ > + em->start = 0; > + em->len = SZ_16K; > + em->block_start = 0; > + em->block_len = SZ_16K; > + ret = btrfs_add_extent_mapping(em_tree, &em, start, len); > + if (ret) > + test_msg("case3 [0x%llx 0x%llx): ret %d\n", > + start, start + len, ret); > + /* > + * Since bytes within em are contiguous, em->block_start is identical to > + * em->start. > + */ > + if (em && > + (start < em->start || start + len > extent_map_end(em) || > + em->start != em->block_start || em->len != em->block_len)) > + test_msg("case3 [0x%llx 0x%llx): ret %d em (start 0x%llx len 0x%llx block_start 0x%llx block_len 0x%llx)\n", > + start, start + len, ret, em->start, em->len, > + em->block_start, em->block_len); > + free_extent_map(em); > +out: > + /* free memory */ > + free_extent_map_tree(em_tree); > +} > + > +/* > + * Test scenario: > + * > + * Suppose that no extent map has been loaded into memory yet. > + * There is a file extent [0, 16K), two jobs are running concurrently > + * against it, t1 is buffered writing to [4K, 8K) and t2 is doing dio > + * read from [0, 4K) or [8K, 12K) or [12K, 16K). > + * > + * t1 goes ahead of t2 and adds em [4K, 8K) into tree. > + * > + * t1 t2 > + * cow_file_range() btrfs_get_extent() > + * -> lookup_extent_mapping() > + * -> add_extent_mapping() > + * -> add_extent_mapping() > + */ > +static void test_case_3(struct extent_map_tree *em_tree) > +{ > + __test_case_3(em_tree, 0); > + __test_case_3(em_tree, SZ_8K); > + __test_case_3(em_tree, (12 * 1024ULL)); > +} > + > int btrfs_test_extent_map() > { > struct extent_map_tree *em_tree; > @@ -196,6 +268,7 @@ int btrfs_test_extent_map() > > test_case_1(em_tree); > test_case_2(em_tree); > + test_case_3(em_tree); > > kfree(em_tree); > return 0; >