From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 2608821A6F108 for ; Tue, 25 Apr 2017 13:39:13 -0700 (PDT) Date: Tue, 25 Apr 2017 14:39:11 -0600 From: Ross Zwisler Subject: Re: [PATCH 2/2] dax: add regression test for stale mmap reads Message-ID: <20170425203911.GC11773@linux.intel.com> References: <20170421034437.4359-1-ross.zwisler@linux.intel.com> <20170424174932.15613-1-ross.zwisler@linux.intel.com> <20170424174932.15613-2-ross.zwisler@linux.intel.com> <20170425112738.GV26397@eguan.usersys.redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20170425112738.GV26397@eguan.usersys.redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Eryu Guan Cc: Jan Kara , Andrew Morton , "Darrick J. Wong" , fstests@vger.kernel.org, Christoph Hellwig , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org List-ID: On Tue, Apr 25, 2017 at 07:27:39PM +0800, Eryu Guan wrote: > On Mon, Apr 24, 2017 at 11:49:32AM -0600, Ross Zwisler wrote: > > This adds a regression test for the following kernel patch: > > > > dax: fix data corruption due to stale mmap reads > > > > Seems that this patch hasn't been merged into linus tree, thus 4.11-rc8 > kernel should fail this test, but it passed for me, tested with 4.11-rc8 > kernel on both ext4 and xfs, with both brd devices and pmem devices > created from "memmap=10G!5G memmap=15G!15G" kernel boot command line. > Did I miss anything? > > # ./check -s ext4_pmem_4k generic/427 > SECTION -- ext4_pmem_4k Ooh, I didn't add this 'ext4_pmem_4k' section goodness, and it's not present in the xfstests/master that I was using. Do you have patches to add that? > RECREATING -- ext4 on /dev/pmem0 > FSTYP -- ext4 > PLATFORM -- Linux/x86_64 hp-dl360g9-15 4.11.0-rc8.kasan > MKFS_OPTIONS -- -b 4096 /dev/pmem1 > MOUNT_OPTIONS -- -o acl,user_xattr -o context=system_u:object_r:root_t:s0 /dev/pmem1 /scratch > > generic/427 1s ... 1s > Ran: generic/427 > Passed all 1 tests Your memmap params look fine. I tested with BRD and PMEM, and with EXT4 and XFS, and all combinations failed for me as expected with v4.11-rc8. One issue could have been that the test file already existed when the test was run. I wasn't removing it between runs earlier, but I've fixed that for v2. Another issue I guess could have been that the hole that we got back from the filesystem was smaller than 2MiB? Can you try running v2 (which I'll post in a second) against a TEST_DEV made with one of the following: ext4: mkfs.ext4 -b 4096 -E stride=512 -F $TEST_DEV xfs: mkfs.xfs -f -d su=2m,sw=1 $TEST_DEV This helps us get 2MiB sized and aligned allocations so we can fault in PMDs, but I'm not sure whether or not it would matter for holes. > Some comments inline. > > > The above patch fixes an issue where users of DAX can suffer data > > corruption from stale mmap reads via the following sequence: > > > > - open an mmap over a 2MiB hole > > > > - read from a 2MiB hole, faulting in a 2MiB zero page > > > > - write to the hole with write(3p). The write succeeds but we incorrectly > > leave the 2MiB zero page mapping intact. > > > > - via the mmap, read the data that was just written. Since the zero page > > mapping is still intact we read back zeroes instead of the new data. > > > > Signed-off-by: Ross Zwisler > > --- > > .gitignore | 1 + > > src/Makefile | 2 +- > > src/t_dax_stale_pmd.c | 56 ++++++++++++++++++++++++++++++++++++++++++ > > tests/generic/427 | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++ > > tests/generic/427.out | 2 ++ > > tests/generic/group | 1 + > > 6 files changed, 129 insertions(+), 1 deletion(-) > > create mode 100644 src/t_dax_stale_pmd.c > > create mode 100755 tests/generic/427 > > create mode 100644 tests/generic/427.out > > > > diff --git a/.gitignore b/.gitignore > > index ded4a61..9664dc9 100644 > > --- a/.gitignore > > +++ b/.gitignore > > @@ -134,6 +134,7 @@ > > /src/renameat2 > > /src/t_rename_overwrite > > /src/t_mmap_dio > > +/src/t_dax_stale_pmd > > > > # dmapi/ binaries > > /dmapi/src/common/cmd/read_invis > > diff --git a/src/Makefile b/src/Makefile > > index abfd873..7e22b50 100644 > > --- a/src/Makefile > > +++ b/src/Makefile > > @@ -12,7 +12,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \ > > godown resvtest writemod makeextents itrash rename \ > > multi_open_unlink dmiperf unwritten_sync genhashnames t_holes \ > > t_mmap_writev t_truncate_cmtime dirhash_collide t_rename_overwrite \ > > - holetest t_truncate_self t_mmap_dio af_unix > > + holetest t_truncate_self t_mmap_dio af_unix t_dax_stale_pmd > > > > LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \ > > preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \ > > diff --git a/src/t_dax_stale_pmd.c b/src/t_dax_stale_pmd.c > > new file mode 100644 > > index 0000000..d0016eb > > --- /dev/null > > +++ b/src/t_dax_stale_pmd.c > > @@ -0,0 +1,56 @@ > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +#define MiB(a) ((a)*1024*1024) > > + > > +void err_exit(char *op) > > +{ > > + fprintf(stderr, "%s: %s\n", op, strerror(errno)); > > + exit(1); > > +} > > + > > +int main(int argc, char *argv[]) > > +{ > > + volatile int a __attribute__((__unused__)); > > + char *buffer = "HELLO WORLD!"; > > + char *data; > > + int fd; > > + > > + if (argc < 2) { > > + printf("Usage: %s \n", basename(argv[0])); > > + exit(0); > > + } > > + > > + fd = open(argv[1], O_RDWR); > > + if (fd < 0) > > + err_exit("fd"); > ^^^^ Nitpick, the "op" should be "open"? > > + > > + data = mmap(NULL, MiB(2), PROT_READ, MAP_SHARED, fd, MiB(2)); > > + > > + /* > > + * This faults in a 2MiB zero page to satisfy the read. > > + * 'a' is volatile so this read doesn't get optimized out. > > + */ > > + a = data[0]; > > + > > + pwrite(fd, buffer, strlen(buffer), MiB(2)); > > + > > + /* > > + * Try and use the mmap to read back the data we just wrote with > > + * pwrite(). If the kernel bug is present the mapping from the 2MiB > > + * zero page will still be intact, and we'll read back zeros instead. > > + */ > > + if (strncmp(buffer, data, strlen(buffer))) > > + err_exit("strncmp mismatch!"); > > strncmp doesn't set errno, this err_exit message might be confusing: > "strncmp mismatch!: Success" Ah, thanks, fixed in v2. > > + > > + close(fd); > > + return 0; > > +} > > diff --git a/tests/generic/427 b/tests/generic/427 > > new file mode 100755 > > index 0000000..baf1099 > > --- /dev/null > > +++ b/tests/generic/427 > > @@ -0,0 +1,68 @@ > > +#! /bin/bash > > +# FS QA Test 427 > > +# > > +# This is a regression test for kernel patch: > > +# dax: fix data corruption due to stale mmap reads > > +# created by Ross Zwisler > > +# > > +#----------------------------------------------------------------------- > > +# Copyright (c) 2017 Intel Corporation. All Rights Reserved. > > +# > > +# This program is free software; you can redistribute it and/or > > +# modify it under the terms of the GNU General Public License as > > +# published by the Free Software Foundation. > > +# > > +# This program is distributed in the hope that it would be useful, > > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > +# GNU General Public License for more details. > > +# > > +# You should have received a copy of the GNU General Public License > > +# along with this program; if not, write the Free Software Foundation, > > +# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA > > +#----------------------------------------------------------------------- > > +# > > + > > +seq=`basename $0` > > +seqres=$RESULT_DIR/$seq > > +echo "QA output created by $seq" > > + > > +here=`pwd` > > +tmp=/tmp/$$ > > +status=1 # failure is the default! > > +trap "_cleanup; exit \$status" 0 1 2 3 15 > > + > > +_cleanup() > > +{ > > + cd / > > + rm -f $tmp.* > > +} > > + > > +# get standard environment, filters and checks > > +. ./common/rc > > +. ./common/filter > > + > > +# remove previous $seqres.full before test > > +rm -f $seqres.full > > + > > +# Modify as appropriate. > > +_supported_fs generic > > +_supported_os Linux > > +_require_scratch_dax > > I don't think dax is a requirement here, this test could run on normal > block device without "-o dax" option too. It won't hurt to run with more > test configurations. And test on nvdimm device with dax mount option > could be one of the test configs, e.g. > > TEST_DEV=/dev/pmem0 > SCRATCH_DEV=/dev/pmem1 > MOUNT_OPTIONS="-o dax" > ... Yep, agreed, fixed in v2. > > +_require_test_program "t_dax_stale_pmd" > > +_require_user > > _require_xfs_io_command "falloc" > > So test _notrun on ext2/3. Fixed in v2. > > + > > +# real QA test starts here > > +_scratch_mkfs >>$seqres.full 2>&1 > > +_scratch_mount "-o dax" > > Same here, dax is not required. Fixed in v2. > > > + > > +$XFS_IO_PROG -f -c "falloc 0 4M" $SCRATCH_MNT/testfile >> $seqres.full 2>&1 > > +chmod 0644 $SCRATCH_MNT/testfile > > +chown $qa_user $SCRATCH_MNT/testfile > > Any specific reason to use $qa_user to run this test? Comments would be > great. Nope, just cargo-culting my way through my first xfstest. :) I've removed this for v2. > Thanks, > Eryu Thanks for the review! > > + > > +_user_do "src/t_dax_stale_pmd $SCRATCH_MNT/testfile" > > + > > +# success, all done > > +echo "Silence is golden" > > +status=0 > > +exit > > diff --git a/tests/generic/427.out b/tests/generic/427.out _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga01.intel.com ([192.55.52.88]:15381 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1032023AbdDYUjN (ORCPT ); Tue, 25 Apr 2017 16:39:13 -0400 Date: Tue, 25 Apr 2017 14:39:11 -0600 From: Ross Zwisler Subject: Re: [PATCH 2/2] dax: add regression test for stale mmap reads Message-ID: <20170425203911.GC11773@linux.intel.com> References: <20170421034437.4359-1-ross.zwisler@linux.intel.com> <20170424174932.15613-1-ross.zwisler@linux.intel.com> <20170424174932.15613-2-ross.zwisler@linux.intel.com> <20170425112738.GV26397@eguan.usersys.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170425112738.GV26397@eguan.usersys.redhat.com> Sender: fstests-owner@vger.kernel.org To: Eryu Guan Cc: Ross Zwisler , fstests@vger.kernel.org, Xiong Zhou , jmoyer@redhat.com, Christoph Hellwig , Dan Williams , "Darrick J. Wong" , Jan Kara , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, Andrew Morton List-ID: On Tue, Apr 25, 2017 at 07:27:39PM +0800, Eryu Guan wrote: > On Mon, Apr 24, 2017 at 11:49:32AM -0600, Ross Zwisler wrote: > > This adds a regression test for the following kernel patch: > > > > dax: fix data corruption due to stale mmap reads > > > > Seems that this patch hasn't been merged into linus tree, thus 4.11-rc8 > kernel should fail this test, but it passed for me, tested with 4.11-rc8 > kernel on both ext4 and xfs, with both brd devices and pmem devices > created from "memmap=10G!5G memmap=15G!15G" kernel boot command line. > Did I miss anything? > > # ./check -s ext4_pmem_4k generic/427 > SECTION -- ext4_pmem_4k Ooh, I didn't add this 'ext4_pmem_4k' section goodness, and it's not present in the xfstests/master that I was using. Do you have patches to add that? > RECREATING -- ext4 on /dev/pmem0 > FSTYP -- ext4 > PLATFORM -- Linux/x86_64 hp-dl360g9-15 4.11.0-rc8.kasan > MKFS_OPTIONS -- -b 4096 /dev/pmem1 > MOUNT_OPTIONS -- -o acl,user_xattr -o context=system_u:object_r:root_t:s0 /dev/pmem1 /scratch > > generic/427 1s ... 1s > Ran: generic/427 > Passed all 1 tests Your memmap params look fine. I tested with BRD and PMEM, and with EXT4 and XFS, and all combinations failed for me as expected with v4.11-rc8. One issue could have been that the test file already existed when the test was run. I wasn't removing it between runs earlier, but I've fixed that for v2. Another issue I guess could have been that the hole that we got back from the filesystem was smaller than 2MiB? Can you try running v2 (which I'll post in a second) against a TEST_DEV made with one of the following: ext4: mkfs.ext4 -b 4096 -E stride=512 -F $TEST_DEV xfs: mkfs.xfs -f -d su=2m,sw=1 $TEST_DEV This helps us get 2MiB sized and aligned allocations so we can fault in PMDs, but I'm not sure whether or not it would matter for holes. > Some comments inline. > > > The above patch fixes an issue where users of DAX can suffer data > > corruption from stale mmap reads via the following sequence: > > > > - open an mmap over a 2MiB hole > > > > - read from a 2MiB hole, faulting in a 2MiB zero page > > > > - write to the hole with write(3p). The write succeeds but we incorrectly > > leave the 2MiB zero page mapping intact. > > > > - via the mmap, read the data that was just written. Since the zero page > > mapping is still intact we read back zeroes instead of the new data. > > > > Signed-off-by: Ross Zwisler > > --- > > .gitignore | 1 + > > src/Makefile | 2 +- > > src/t_dax_stale_pmd.c | 56 ++++++++++++++++++++++++++++++++++++++++++ > > tests/generic/427 | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++ > > tests/generic/427.out | 2 ++ > > tests/generic/group | 1 + > > 6 files changed, 129 insertions(+), 1 deletion(-) > > create mode 100644 src/t_dax_stale_pmd.c > > create mode 100755 tests/generic/427 > > create mode 100644 tests/generic/427.out > > > > diff --git a/.gitignore b/.gitignore > > index ded4a61..9664dc9 100644 > > --- a/.gitignore > > +++ b/.gitignore > > @@ -134,6 +134,7 @@ > > /src/renameat2 > > /src/t_rename_overwrite > > /src/t_mmap_dio > > +/src/t_dax_stale_pmd > > > > # dmapi/ binaries > > /dmapi/src/common/cmd/read_invis > > diff --git a/src/Makefile b/src/Makefile > > index abfd873..7e22b50 100644 > > --- a/src/Makefile > > +++ b/src/Makefile > > @@ -12,7 +12,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \ > > godown resvtest writemod makeextents itrash rename \ > > multi_open_unlink dmiperf unwritten_sync genhashnames t_holes \ > > t_mmap_writev t_truncate_cmtime dirhash_collide t_rename_overwrite \ > > - holetest t_truncate_self t_mmap_dio af_unix > > + holetest t_truncate_self t_mmap_dio af_unix t_dax_stale_pmd > > > > LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \ > > preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \ > > diff --git a/src/t_dax_stale_pmd.c b/src/t_dax_stale_pmd.c > > new file mode 100644 > > index 0000000..d0016eb > > --- /dev/null > > +++ b/src/t_dax_stale_pmd.c > > @@ -0,0 +1,56 @@ > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +#define MiB(a) ((a)*1024*1024) > > + > > +void err_exit(char *op) > > +{ > > + fprintf(stderr, "%s: %s\n", op, strerror(errno)); > > + exit(1); > > +} > > + > > +int main(int argc, char *argv[]) > > +{ > > + volatile int a __attribute__((__unused__)); > > + char *buffer = "HELLO WORLD!"; > > + char *data; > > + int fd; > > + > > + if (argc < 2) { > > + printf("Usage: %s \n", basename(argv[0])); > > + exit(0); > > + } > > + > > + fd = open(argv[1], O_RDWR); > > + if (fd < 0) > > + err_exit("fd"); > ^^^^ Nitpick, the "op" should be "open"? > > + > > + data = mmap(NULL, MiB(2), PROT_READ, MAP_SHARED, fd, MiB(2)); > > + > > + /* > > + * This faults in a 2MiB zero page to satisfy the read. > > + * 'a' is volatile so this read doesn't get optimized out. > > + */ > > + a = data[0]; > > + > > + pwrite(fd, buffer, strlen(buffer), MiB(2)); > > + > > + /* > > + * Try and use the mmap to read back the data we just wrote with > > + * pwrite(). If the kernel bug is present the mapping from the 2MiB > > + * zero page will still be intact, and we'll read back zeros instead. > > + */ > > + if (strncmp(buffer, data, strlen(buffer))) > > + err_exit("strncmp mismatch!"); > > strncmp doesn't set errno, this err_exit message might be confusing: > "strncmp mismatch!: Success" Ah, thanks, fixed in v2. > > + > > + close(fd); > > + return 0; > > +} > > diff --git a/tests/generic/427 b/tests/generic/427 > > new file mode 100755 > > index 0000000..baf1099 > > --- /dev/null > > +++ b/tests/generic/427 > > @@ -0,0 +1,68 @@ > > +#! /bin/bash > > +# FS QA Test 427 > > +# > > +# This is a regression test for kernel patch: > > +# dax: fix data corruption due to stale mmap reads > > +# created by Ross Zwisler > > +# > > +#----------------------------------------------------------------------- > > +# Copyright (c) 2017 Intel Corporation. All Rights Reserved. > > +# > > +# This program is free software; you can redistribute it and/or > > +# modify it under the terms of the GNU General Public License as > > +# published by the Free Software Foundation. > > +# > > +# This program is distributed in the hope that it would be useful, > > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > +# GNU General Public License for more details. > > +# > > +# You should have received a copy of the GNU General Public License > > +# along with this program; if not, write the Free Software Foundation, > > +# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA > > +#----------------------------------------------------------------------- > > +# > > + > > +seq=`basename $0` > > +seqres=$RESULT_DIR/$seq > > +echo "QA output created by $seq" > > + > > +here=`pwd` > > +tmp=/tmp/$$ > > +status=1 # failure is the default! > > +trap "_cleanup; exit \$status" 0 1 2 3 15 > > + > > +_cleanup() > > +{ > > + cd / > > + rm -f $tmp.* > > +} > > + > > +# get standard environment, filters and checks > > +. ./common/rc > > +. ./common/filter > > + > > +# remove previous $seqres.full before test > > +rm -f $seqres.full > > + > > +# Modify as appropriate. > > +_supported_fs generic > > +_supported_os Linux > > +_require_scratch_dax > > I don't think dax is a requirement here, this test could run on normal > block device without "-o dax" option too. It won't hurt to run with more > test configurations. And test on nvdimm device with dax mount option > could be one of the test configs, e.g. > > TEST_DEV=/dev/pmem0 > SCRATCH_DEV=/dev/pmem1 > MOUNT_OPTIONS="-o dax" > ... Yep, agreed, fixed in v2. > > +_require_test_program "t_dax_stale_pmd" > > +_require_user > > _require_xfs_io_command "falloc" > > So test _notrun on ext2/3. Fixed in v2. > > + > > +# real QA test starts here > > +_scratch_mkfs >>$seqres.full 2>&1 > > +_scratch_mount "-o dax" > > Same here, dax is not required. Fixed in v2. > > > + > > +$XFS_IO_PROG -f -c "falloc 0 4M" $SCRATCH_MNT/testfile >> $seqres.full 2>&1 > > +chmod 0644 $SCRATCH_MNT/testfile > > +chown $qa_user $SCRATCH_MNT/testfile > > Any specific reason to use $qa_user to run this test? Comments would be > great. Nope, just cargo-culting my way through my first xfstest. :) I've removed this for v2. > Thanks, > Eryu Thanks for the review! > > + > > +_user_do "src/t_dax_stale_pmd $SCRATCH_MNT/testfile" > > + > > +# success, all done > > +echo "Silence is golden" > > +status=0 > > +exit > > diff --git a/tests/generic/427.out b/tests/generic/427.out From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 25 Apr 2017 14:39:11 -0600 From: Ross Zwisler To: Eryu Guan Cc: Ross Zwisler , fstests@vger.kernel.org, Xiong Zhou , jmoyer@redhat.com, Christoph Hellwig , Dan Williams , "Darrick J. Wong" , Jan Kara , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, Andrew Morton Subject: Re: [PATCH 2/2] dax: add regression test for stale mmap reads Message-ID: <20170425203911.GC11773@linux.intel.com> References: <20170421034437.4359-1-ross.zwisler@linux.intel.com> <20170424174932.15613-1-ross.zwisler@linux.intel.com> <20170424174932.15613-2-ross.zwisler@linux.intel.com> <20170425112738.GV26397@eguan.usersys.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170425112738.GV26397@eguan.usersys.redhat.com> Sender: owner-linux-mm@kvack.org List-ID: On Tue, Apr 25, 2017 at 07:27:39PM +0800, Eryu Guan wrote: > On Mon, Apr 24, 2017 at 11:49:32AM -0600, Ross Zwisler wrote: > > This adds a regression test for the following kernel patch: > > > > dax: fix data corruption due to stale mmap reads > > > > Seems that this patch hasn't been merged into linus tree, thus 4.11-rc8 > kernel should fail this test, but it passed for me, tested with 4.11-rc8 > kernel on both ext4 and xfs, with both brd devices and pmem devices > created from "memmap=10G!5G memmap=15G!15G" kernel boot command line. > Did I miss anything? > > # ./check -s ext4_pmem_4k generic/427 > SECTION -- ext4_pmem_4k Ooh, I didn't add this 'ext4_pmem_4k' section goodness, and it's not present in the xfstests/master that I was using. Do you have patches to add that? > RECREATING -- ext4 on /dev/pmem0 > FSTYP -- ext4 > PLATFORM -- Linux/x86_64 hp-dl360g9-15 4.11.0-rc8.kasan > MKFS_OPTIONS -- -b 4096 /dev/pmem1 > MOUNT_OPTIONS -- -o acl,user_xattr -o context=system_u:object_r:root_t:s0 /dev/pmem1 /scratch > > generic/427 1s ... 1s > Ran: generic/427 > Passed all 1 tests Your memmap params look fine. I tested with BRD and PMEM, and with EXT4 and XFS, and all combinations failed for me as expected with v4.11-rc8. One issue could have been that the test file already existed when the test was run. I wasn't removing it between runs earlier, but I've fixed that for v2. Another issue I guess could have been that the hole that we got back from the filesystem was smaller than 2MiB? Can you try running v2 (which I'll post in a second) against a TEST_DEV made with one of the following: ext4: mkfs.ext4 -b 4096 -E stride=512 -F $TEST_DEV xfs: mkfs.xfs -f -d su=2m,sw=1 $TEST_DEV This helps us get 2MiB sized and aligned allocations so we can fault in PMDs, but I'm not sure whether or not it would matter for holes. > Some comments inline. > > > The above patch fixes an issue where users of DAX can suffer data > > corruption from stale mmap reads via the following sequence: > > > > - open an mmap over a 2MiB hole > > > > - read from a 2MiB hole, faulting in a 2MiB zero page > > > > - write to the hole with write(3p). The write succeeds but we incorrectly > > leave the 2MiB zero page mapping intact. > > > > - via the mmap, read the data that was just written. Since the zero page > > mapping is still intact we read back zeroes instead of the new data. > > > > Signed-off-by: Ross Zwisler > > --- > > .gitignore | 1 + > > src/Makefile | 2 +- > > src/t_dax_stale_pmd.c | 56 ++++++++++++++++++++++++++++++++++++++++++ > > tests/generic/427 | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++ > > tests/generic/427.out | 2 ++ > > tests/generic/group | 1 + > > 6 files changed, 129 insertions(+), 1 deletion(-) > > create mode 100644 src/t_dax_stale_pmd.c > > create mode 100755 tests/generic/427 > > create mode 100644 tests/generic/427.out > > > > diff --git a/.gitignore b/.gitignore > > index ded4a61..9664dc9 100644 > > --- a/.gitignore > > +++ b/.gitignore > > @@ -134,6 +134,7 @@ > > /src/renameat2 > > /src/t_rename_overwrite > > /src/t_mmap_dio > > +/src/t_dax_stale_pmd > > > > # dmapi/ binaries > > /dmapi/src/common/cmd/read_invis > > diff --git a/src/Makefile b/src/Makefile > > index abfd873..7e22b50 100644 > > --- a/src/Makefile > > +++ b/src/Makefile > > @@ -12,7 +12,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \ > > godown resvtest writemod makeextents itrash rename \ > > multi_open_unlink dmiperf unwritten_sync genhashnames t_holes \ > > t_mmap_writev t_truncate_cmtime dirhash_collide t_rename_overwrite \ > > - holetest t_truncate_self t_mmap_dio af_unix > > + holetest t_truncate_self t_mmap_dio af_unix t_dax_stale_pmd > > > > LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \ > > preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \ > > diff --git a/src/t_dax_stale_pmd.c b/src/t_dax_stale_pmd.c > > new file mode 100644 > > index 0000000..d0016eb > > --- /dev/null > > +++ b/src/t_dax_stale_pmd.c > > @@ -0,0 +1,56 @@ > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +#define MiB(a) ((a)*1024*1024) > > + > > +void err_exit(char *op) > > +{ > > + fprintf(stderr, "%s: %s\n", op, strerror(errno)); > > + exit(1); > > +} > > + > > +int main(int argc, char *argv[]) > > +{ > > + volatile int a __attribute__((__unused__)); > > + char *buffer = "HELLO WORLD!"; > > + char *data; > > + int fd; > > + > > + if (argc < 2) { > > + printf("Usage: %s \n", basename(argv[0])); > > + exit(0); > > + } > > + > > + fd = open(argv[1], O_RDWR); > > + if (fd < 0) > > + err_exit("fd"); > ^^^^ Nitpick, the "op" should be "open"? > > + > > + data = mmap(NULL, MiB(2), PROT_READ, MAP_SHARED, fd, MiB(2)); > > + > > + /* > > + * This faults in a 2MiB zero page to satisfy the read. > > + * 'a' is volatile so this read doesn't get optimized out. > > + */ > > + a = data[0]; > > + > > + pwrite(fd, buffer, strlen(buffer), MiB(2)); > > + > > + /* > > + * Try and use the mmap to read back the data we just wrote with > > + * pwrite(). If the kernel bug is present the mapping from the 2MiB > > + * zero page will still be intact, and we'll read back zeros instead. > > + */ > > + if (strncmp(buffer, data, strlen(buffer))) > > + err_exit("strncmp mismatch!"); > > strncmp doesn't set errno, this err_exit message might be confusing: > "strncmp mismatch!: Success" Ah, thanks, fixed in v2. > > + > > + close(fd); > > + return 0; > > +} > > diff --git a/tests/generic/427 b/tests/generic/427 > > new file mode 100755 > > index 0000000..baf1099 > > --- /dev/null > > +++ b/tests/generic/427 > > @@ -0,0 +1,68 @@ > > +#! /bin/bash > > +# FS QA Test 427 > > +# > > +# This is a regression test for kernel patch: > > +# dax: fix data corruption due to stale mmap reads > > +# created by Ross Zwisler > > +# > > +#----------------------------------------------------------------------- > > +# Copyright (c) 2017 Intel Corporation. All Rights Reserved. > > +# > > +# This program is free software; you can redistribute it and/or > > +# modify it under the terms of the GNU General Public License as > > +# published by the Free Software Foundation. > > +# > > +# This program is distributed in the hope that it would be useful, > > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > +# GNU General Public License for more details. > > +# > > +# You should have received a copy of the GNU General Public License > > +# along with this program; if not, write the Free Software Foundation, > > +# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA > > +#----------------------------------------------------------------------- > > +# > > + > > +seq=`basename $0` > > +seqres=$RESULT_DIR/$seq > > +echo "QA output created by $seq" > > + > > +here=`pwd` > > +tmp=/tmp/$$ > > +status=1 # failure is the default! > > +trap "_cleanup; exit \$status" 0 1 2 3 15 > > + > > +_cleanup() > > +{ > > + cd / > > + rm -f $tmp.* > > +} > > + > > +# get standard environment, filters and checks > > +. ./common/rc > > +. ./common/filter > > + > > +# remove previous $seqres.full before test > > +rm -f $seqres.full > > + > > +# Modify as appropriate. > > +_supported_fs generic > > +_supported_os Linux > > +_require_scratch_dax > > I don't think dax is a requirement here, this test could run on normal > block device without "-o dax" option too. It won't hurt to run with more > test configurations. And test on nvdimm device with dax mount option > could be one of the test configs, e.g. > > TEST_DEV=/dev/pmem0 > SCRATCH_DEV=/dev/pmem1 > MOUNT_OPTIONS="-o dax" > ... Yep, agreed, fixed in v2. > > +_require_test_program "t_dax_stale_pmd" > > +_require_user > > _require_xfs_io_command "falloc" > > So test _notrun on ext2/3. Fixed in v2. > > + > > +# real QA test starts here > > +_scratch_mkfs >>$seqres.full 2>&1 > > +_scratch_mount "-o dax" > > Same here, dax is not required. Fixed in v2. > > > + > > +$XFS_IO_PROG -f -c "falloc 0 4M" $SCRATCH_MNT/testfile >> $seqres.full 2>&1 > > +chmod 0644 $SCRATCH_MNT/testfile > > +chown $qa_user $SCRATCH_MNT/testfile > > Any specific reason to use $qa_user to run this test? Comments would be > great. Nope, just cargo-culting my way through my first xfstest. :) I've removed this for v2. > Thanks, > Eryu Thanks for the review! > > + > > +_user_do "src/t_dax_stale_pmd $SCRATCH_MNT/testfile" > > + > > +# success, all done > > +echo "Silence is golden" > > +status=0 > > +exit > > diff --git a/tests/generic/427.out b/tests/generic/427.out -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org