diff mbox series

[v3] generic/808: add a regression test for fiemap into an mmap range

Message ID 076b7d22d653a046bf3710c4fa04cc155b6cf07b.1710945314.git.josef@toxicpanda.com (mailing list archive)
State New, archived
Headers show
Series [v3] generic/808: add a regression test for fiemap into an mmap range | expand

Commit Message

Josef Bacik March 20, 2024, 2:36 p.m. UTC 
Btrfs had a deadlock that you could trigger by mmap'ing a large file and
using that as the buffer for fiemap.  This test adds a c program to do
this, and the fstest creates a large enough file and then runs the
reproducer on the file.  Without the fix btrfs deadlocks, with the fix
we pass fine.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
v2->v3:
- Add fiemap-fault to .gitignore
- Added a _cleanup() helper
- Just let the output of fiemap-fault go instead of using || _fail
- Added the munmap
- Moved $dst to $TEST_DIR/$seq

 .gitignore            |  1 +
 src/Makefile          |  2 +-
 src/fiemap-fault.c    | 74 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/808     | 48 ++++++++++++++++++++++++++++
 tests/generic/808.out |  2 ++
 5 files changed, 126 insertions(+), 1 deletion(-)
 create mode 100644 src/fiemap-fault.c
 create mode 100755 tests/generic/808
 create mode 100644 tests/generic/808.out

Comments

Filipe Manana March 20, 2024, 2:52 p.m. UTC | #1 
On Wed, Mar 20, 2024 at 2:36 PM Josef Bacik <josef@toxicpanda.com> wrote:
>
> Btrfs had a deadlock that you could trigger by mmap'ing a large file and
> using that as the buffer for fiemap.  This test adds a c program to do
> this, and the fstest creates a large enough file and then runs the
> reproducer on the file.  Without the fix btrfs deadlocks, with the fix
> we pass fine.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Looks good to me now, thanks.

> ---
> v2->v3:
> - Add fiemap-fault to .gitignore
> - Added a _cleanup() helper
> - Just let the output of fiemap-fault go instead of using || _fail
> - Added the munmap
> - Moved $dst to $TEST_DIR/$seq
>
>  .gitignore            |  1 +
>  src/Makefile          |  2 +-
>  src/fiemap-fault.c    | 74 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/808     | 48 ++++++++++++++++++++++++++++
>  tests/generic/808.out |  2 ++
>  5 files changed, 126 insertions(+), 1 deletion(-)
>  create mode 100644 src/fiemap-fault.c
>  create mode 100755 tests/generic/808
>  create mode 100644 tests/generic/808.out
>
> diff --git a/.gitignore b/.gitignore
> index 3b160209..f0fb72bd 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -205,6 +205,7 @@ tags
>  /src/vfs/mount-idmapped
>  /src/log-writes/replay-log
>  /src/perf/*.pyc
> +/src/filemap-fault
>
>  # Symlinked files
>  /tests/generic/035.out
> diff --git a/src/Makefile b/src/Makefile
> index e7442487..ab98a06f 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -34,7 +34,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
>         attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
>         fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail \
>         detached_mounts_propagation ext4_resize t_readdir_3 splice2pipe \
> -       uuid_ioctl t_snapshot_deleted_subvolume
> +       uuid_ioctl t_snapshot_deleted_subvolume fiemap-fault
>
>  EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
>               btrfs_crc32c_forged_name.py popdir.pl popattr.py \
> diff --git a/src/fiemap-fault.c b/src/fiemap-fault.c
> new file mode 100644
> index 00000000..73260068
> --- /dev/null
> +++ b/src/fiemap-fault.c
> @@ -0,0 +1,74 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
> + */
> +
> +#include <sys/ioctl.h>
> +#include <sys/mman.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <linux/fs.h>
> +#include <linux/types.h>
> +#include <linux/fiemap.h>
> +#include <err.h>
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <string.h>
> +#include <unistd.h>
> +
> +int prep_mmap_buffer(int fd, void **addr)
> +{
> +       struct stat st;
> +       int ret;
> +
> +       ret = fstat(fd, &st);
> +       if (ret)
> +               err(1, "failed to stat %d", fd);
> +
> +       *addr = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
> +       if (*addr == MAP_FAILED)
> +               err(1, "failed to mmap %d", fd);
> +
> +       return st.st_size;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +       struct fiemap *fiemap;
> +       size_t sz, last = 0;
> +       void *buf = NULL;
> +       int ret, fd;
> +
> +       if (argc != 2)
> +               errx(1, "no in and out file name arguments given");
> +
> +       fd = open(argv[1], O_RDWR, 0666);
> +       if (fd == -1)
> +               err(1, "failed to open %s", argv[1]);
> +
> +       sz = prep_mmap_buffer(fd, &buf);
> +
> +       fiemap = (struct fiemap *)buf;
> +       fiemap->fm_flags = 0;
> +       fiemap->fm_extent_count = (sz - sizeof(struct fiemap)) /
> +                                 sizeof(struct fiemap_extent);
> +
> +       while (last < sz) {
> +               int i;
> +
> +               fiemap->fm_start = last;
> +               fiemap->fm_length = sz - last;
> +
> +               ret = ioctl(fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
> +               if (ret < 0)
> +                       err(1, "fiemap failed %d", errno);
> +               for (i = 0; i < fiemap->fm_mapped_extents; i++)
> +                      last = fiemap->fm_extents[i].fe_logical +
> +                              fiemap->fm_extents[i].fe_length;
> +       }
> +
> +       munmap(buf, sz);
> +       close(fd);
> +       return 0;
> +}
> diff --git a/tests/generic/808 b/tests/generic/808
> new file mode 100755
> index 00000000..36015f35
> --- /dev/null
> +++ b/tests/generic/808
> @@ -0,0 +1,48 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
> +#
> +# FS QA Test 808
> +#
> +# Test fiemap into an mmaped buffer of the same file
> +#
> +# Create a reasonably large file, then run a program which mmaps it and uses
> +# that as a buffer for an fiemap call.  This is a regression test for btrfs
> +# where we used to hold a lock for the duration of the fiemap call which would
> +# result in a deadlock if we page faulted.
> +#
> +. ./common/preamble
> +_begin_fstest quick auto fiemap
> +[ $FSTYP == "btrfs" ] && \
> +       _fixed_by_kernel_commit b0ad381fa769 \
> +               "btrfs: fix deadlock with fiemap and extent locking"
> +
> +_cleanup()
> +{
> +       rm -f $dst
> +       cd /
> +       rm -r -f $tmp.*
> +}
> +
> +# real QA test starts here
> +_supported_fs generic
> +_require_test
> +_require_odirect
> +_require_test_program fiemap-fault
> +dst=$TEST_DIR/$seq/fiemap-fault
> +
> +mkdir -p $TEST_DIR/$seq
> +
> +echo "Silence is golden"
> +
> +for i in $(seq 0 2 1000)
> +do
> +       $XFS_IO_PROG -d -f -c "pwrite -q $((i * 4096)) 4096" $dst
> +done
> +
> +$here/src/fiemap-fault $dst
> +
> +# success, all done
> +status=$?
> +exit
> +
> diff --git a/tests/generic/808.out b/tests/generic/808.out
> new file mode 100644
> index 00000000..88253428
> --- /dev/null
> +++ b/tests/generic/808.out
> @@ -0,0 +1,2 @@
> +QA output created by 808
> +Silence is golden
> --
> 2.43.0
>
>
Darrick J. Wong March 20, 2024, 3:25 p.m. UTC | #2 
On Wed, Mar 20, 2024 at 10:36:42AM -0400, Josef Bacik wrote:
> Btrfs had a deadlock that you could trigger by mmap'ing a large file and
> using that as the buffer for fiemap.  This test adds a c program to do
> this, and the fstest creates a large enough file and then runs the
> reproducer on the file.  Without the fix btrfs deadlocks, with the fix
> we pass fine.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
> v2->v3:
> - Add fiemap-fault to .gitignore
> - Added a _cleanup() helper
> - Just let the output of fiemap-fault go instead of using || _fail
> - Added the munmap
> - Moved $dst to $TEST_DIR/$seq
> 
>  .gitignore            |  1 +
>  src/Makefile          |  2 +-
>  src/fiemap-fault.c    | 74 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/808     | 48 ++++++++++++++++++++++++++++
>  tests/generic/808.out |  2 ++
>  5 files changed, 126 insertions(+), 1 deletion(-)
>  create mode 100644 src/fiemap-fault.c
>  create mode 100755 tests/generic/808
>  create mode 100644 tests/generic/808.out
> 
> diff --git a/.gitignore b/.gitignore
> index 3b160209..f0fb72bd 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -205,6 +205,7 @@ tags
>  /src/vfs/mount-idmapped
>  /src/log-writes/replay-log
>  /src/perf/*.pyc
> +/src/filemap-fault
>  
>  # Symlinked files
>  /tests/generic/035.out
> diff --git a/src/Makefile b/src/Makefile
> index e7442487..ab98a06f 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -34,7 +34,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
>  	attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
>  	fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail \
>  	detached_mounts_propagation ext4_resize t_readdir_3 splice2pipe \
> -	uuid_ioctl t_snapshot_deleted_subvolume
> +	uuid_ioctl t_snapshot_deleted_subvolume fiemap-fault
>  
>  EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
>  	      btrfs_crc32c_forged_name.py popdir.pl popattr.py \
> diff --git a/src/fiemap-fault.c b/src/fiemap-fault.c
> new file mode 100644
> index 00000000..73260068
> --- /dev/null
> +++ b/src/fiemap-fault.c
> @@ -0,0 +1,74 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
> + */
> +
> +#include <sys/ioctl.h>
> +#include <sys/mman.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <linux/fs.h>
> +#include <linux/types.h>
> +#include <linux/fiemap.h>
> +#include <err.h>
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <string.h>
> +#include <unistd.h>
> +
> +int prep_mmap_buffer(int fd, void **addr)
> +{
> +	struct stat st;
> +	int ret;
> +
> +	ret = fstat(fd, &st);
> +	if (ret)
> +		err(1, "failed to stat %d", fd);
> +
> +	*addr = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
> +	if (*addr == MAP_FAILED)
> +		err(1, "failed to mmap %d", fd);
> +
> +	return st.st_size;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	struct fiemap *fiemap;
> +	size_t sz, last = 0;
> +	void *buf = NULL;
> +	int ret, fd;
> +
> +	if (argc != 2)
> +		errx(1, "no in and out file name arguments given");
> +
> +	fd = open(argv[1], O_RDWR, 0666);
> +	if (fd == -1)
> +		err(1, "failed to open %s", argv[1]);
> +
> +	sz = prep_mmap_buffer(fd, &buf);
> +
> +	fiemap = (struct fiemap *)buf;
> +	fiemap->fm_flags = 0;
> +	fiemap->fm_extent_count = (sz - sizeof(struct fiemap)) /
> +				  sizeof(struct fiemap_extent);
> +
> +	while (last < sz) {
> +		int i;
> +
> +		fiemap->fm_start = last;
> +		fiemap->fm_length = sz - last;
> +
> +		ret = ioctl(fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
> +		if (ret < 0)
> +			err(1, "fiemap failed %d", errno);
> +		for (i = 0; i < fiemap->fm_mapped_extents; i++)
> +		       last = fiemap->fm_extents[i].fe_logical +
> +			       fiemap->fm_extents[i].fe_length;
> +	}
> +
> +	munmap(buf, sz);
> +	close(fd);
> +	return 0;
> +}
> diff --git a/tests/generic/808 b/tests/generic/808
> new file mode 100755
> index 00000000..36015f35
> --- /dev/null
> +++ b/tests/generic/808
> @@ -0,0 +1,48 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
> +#
> +# FS QA Test 808
> +#
> +# Test fiemap into an mmaped buffer of the same file
> +#
> +# Create a reasonably large file, then run a program which mmaps it and uses
> +# that as a buffer for an fiemap call.  This is a regression test for btrfs
> +# where we used to hold a lock for the duration of the fiemap call which would
> +# result in a deadlock if we page faulted.
> +#
> +. ./common/preamble
> +_begin_fstest quick auto fiemap
> +[ $FSTYP == "btrfs" ] && \
> +	_fixed_by_kernel_commit b0ad381fa769 \
> +		"btrfs: fix deadlock with fiemap and extent locking"
> +
> +_cleanup()
> +{
> +	rm -f $dst
> +	cd /
> +	rm -r -f $tmp.*
> +}
> +
> +# real QA test starts here
> +_supported_fs generic
> +_require_test
> +_require_odirect
> +_require_test_program fiemap-fault
> +dst=$TEST_DIR/$seq/fiemap-fault
> +
> +mkdir -p $TEST_DIR/$seq
> +
> +echo "Silence is golden"
> +
> +for i in $(seq 0 2 1000)
> +do
> +	$XFS_IO_PROG -d -f -c "pwrite -q $((i * 4096)) 4096" $dst
> +done

I don't know if there's a specific reason that this does directio writes
at alternating offsets other than forcing allocations, but usually we do:

$XFS_IO_PROG -f -c "pwrite -q 0 409600" $dst
$src/punch-alternating $dst

to generate a file with a bunch of extent records.  Also, since this is
a generic test that wants to create a file with sparse holes, it really
ought to be querying the file's allocation unit size:

blksz=$(_get_file_block_size $TEST_DIR)
$XFS_IO_PROG -f -c "pwrite -q 0 $((blksz * 100))" $dst

--D

> +
> +$here/src/fiemap-fault $dst
> +
> +# success, all done
> +status=$?
> +exit
> +
> diff --git a/tests/generic/808.out b/tests/generic/808.out
> new file mode 100644
> index 00000000..88253428
> --- /dev/null
> +++ b/tests/generic/808.out
> @@ -0,0 +1,2 @@
> +QA output created by 808
> +Silence is golden
> -- 
> 2.43.0
> 
>
Josef Bacik March 20, 2024, 3:37 p.m. UTC | #3 
On Wed, Mar 20, 2024 at 08:25:31AM -0700, Darrick J. Wong wrote:
> On Wed, Mar 20, 2024 at 10:36:42AM -0400, Josef Bacik wrote:
> > Btrfs had a deadlock that you could trigger by mmap'ing a large file and
> > using that as the buffer for fiemap.  This test adds a c program to do
> > this, and the fstest creates a large enough file and then runs the
> > reproducer on the file.  Without the fix btrfs deadlocks, with the fix
> > we pass fine.
> > 
> > Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> > ---
> > v2->v3:
> > - Add fiemap-fault to .gitignore
> > - Added a _cleanup() helper
> > - Just let the output of fiemap-fault go instead of using || _fail
> > - Added the munmap
> > - Moved $dst to $TEST_DIR/$seq
> > 
> >  .gitignore            |  1 +
> >  src/Makefile          |  2 +-
> >  src/fiemap-fault.c    | 74 +++++++++++++++++++++++++++++++++++++++++++
> >  tests/generic/808     | 48 ++++++++++++++++++++++++++++
> >  tests/generic/808.out |  2 ++
> >  5 files changed, 126 insertions(+), 1 deletion(-)
> >  create mode 100644 src/fiemap-fault.c
> >  create mode 100755 tests/generic/808
> >  create mode 100644 tests/generic/808.out
> > 
> > diff --git a/.gitignore b/.gitignore
> > index 3b160209..f0fb72bd 100644
> > --- a/.gitignore
> > +++ b/.gitignore
> > @@ -205,6 +205,7 @@ tags
> >  /src/vfs/mount-idmapped
> >  /src/log-writes/replay-log
> >  /src/perf/*.pyc
> > +/src/filemap-fault
> >  
> >  # Symlinked files
> >  /tests/generic/035.out
> > diff --git a/src/Makefile b/src/Makefile
> > index e7442487..ab98a06f 100644
> > --- a/src/Makefile
> > +++ b/src/Makefile
> > @@ -34,7 +34,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
> >  	attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
> >  	fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail \
> >  	detached_mounts_propagation ext4_resize t_readdir_3 splice2pipe \
> > -	uuid_ioctl t_snapshot_deleted_subvolume
> > +	uuid_ioctl t_snapshot_deleted_subvolume fiemap-fault
> >  
> >  EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
> >  	      btrfs_crc32c_forged_name.py popdir.pl popattr.py \
> > diff --git a/src/fiemap-fault.c b/src/fiemap-fault.c
> > new file mode 100644
> > index 00000000..73260068
> > --- /dev/null
> > +++ b/src/fiemap-fault.c
> > @@ -0,0 +1,74 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
> > + */
> > +
> > +#include <sys/ioctl.h>
> > +#include <sys/mman.h>
> > +#include <sys/types.h>
> > +#include <sys/stat.h>
> > +#include <linux/fs.h>
> > +#include <linux/types.h>
> > +#include <linux/fiemap.h>
> > +#include <err.h>
> > +#include <errno.h>
> > +#include <fcntl.h>
> > +#include <stdio.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +
> > +int prep_mmap_buffer(int fd, void **addr)
> > +{
> > +	struct stat st;
> > +	int ret;
> > +
> > +	ret = fstat(fd, &st);
> > +	if (ret)
> > +		err(1, "failed to stat %d", fd);
> > +
> > +	*addr = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
> > +	if (*addr == MAP_FAILED)
> > +		err(1, "failed to mmap %d", fd);
> > +
> > +	return st.st_size;
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +	struct fiemap *fiemap;
> > +	size_t sz, last = 0;
> > +	void *buf = NULL;
> > +	int ret, fd;
> > +
> > +	if (argc != 2)
> > +		errx(1, "no in and out file name arguments given");
> > +
> > +	fd = open(argv[1], O_RDWR, 0666);
> > +	if (fd == -1)
> > +		err(1, "failed to open %s", argv[1]);
> > +
> > +	sz = prep_mmap_buffer(fd, &buf);
> > +
> > +	fiemap = (struct fiemap *)buf;
> > +	fiemap->fm_flags = 0;
> > +	fiemap->fm_extent_count = (sz - sizeof(struct fiemap)) /
> > +				  sizeof(struct fiemap_extent);
> > +
> > +	while (last < sz) {
> > +		int i;
> > +
> > +		fiemap->fm_start = last;
> > +		fiemap->fm_length = sz - last;
> > +
> > +		ret = ioctl(fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
> > +		if (ret < 0)
> > +			err(1, "fiemap failed %d", errno);
> > +		for (i = 0; i < fiemap->fm_mapped_extents; i++)
> > +		       last = fiemap->fm_extents[i].fe_logical +
> > +			       fiemap->fm_extents[i].fe_length;
> > +	}
> > +
> > +	munmap(buf, sz);
> > +	close(fd);
> > +	return 0;
> > +}
> > diff --git a/tests/generic/808 b/tests/generic/808
> > new file mode 100755
> > index 00000000..36015f35
> > --- /dev/null
> > +++ b/tests/generic/808
> > @@ -0,0 +1,48 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
> > +#
> > +# FS QA Test 808
> > +#
> > +# Test fiemap into an mmaped buffer of the same file
> > +#
> > +# Create a reasonably large file, then run a program which mmaps it and uses
> > +# that as a buffer for an fiemap call.  This is a regression test for btrfs
> > +# where we used to hold a lock for the duration of the fiemap call which would
> > +# result in a deadlock if we page faulted.
> > +#
> > +. ./common/preamble
> > +_begin_fstest quick auto fiemap
> > +[ $FSTYP == "btrfs" ] && \
> > +	_fixed_by_kernel_commit b0ad381fa769 \
> > +		"btrfs: fix deadlock with fiemap and extent locking"
> > +
> > +_cleanup()
> > +{
> > +	rm -f $dst
> > +	cd /
> > +	rm -r -f $tmp.*
> > +}
> > +
> > +# real QA test starts here
> > +_supported_fs generic
> > +_require_test
> > +_require_odirect
> > +_require_test_program fiemap-fault
> > +dst=$TEST_DIR/$seq/fiemap-fault
> > +
> > +mkdir -p $TEST_DIR/$seq
> > +
> > +echo "Silence is golden"
> > +
> > +for i in $(seq 0 2 1000)
> > +do
> > +	$XFS_IO_PROG -d -f -c "pwrite -q $((i * 4096)) 4096" $dst
> > +done
> 
> I don't know if there's a specific reason that this does directio writes
> at alternating offsets other than forcing allocations, but usually we do:
> 
> $XFS_IO_PROG -f -c "pwrite -q 0 409600" $dst
> $src/punch-alternating $dst
> 
> to generate a file with a bunch of extent records.  Also, since this is
> a generic test that wants to create a file with sparse holes, it really
> ought to be querying the file's allocation unit size:
> 
> blksz=$(_get_file_block_size $TEST_DIR)
> $XFS_IO_PROG -f -c "pwrite -q 0 $((blksz * 100))" $dst

Ok I can do that instead, you're correct, all I want is a bunch of extents, and
for btrfs at least doing alternating directio writes to get that.  Thanks,

Josef
Anand Jain March 21, 2024, 4:20 a.m. UTC | #4 
On 3/20/24 20:06, Josef Bacik wrote:
> Btrfs had a deadlock that you could trigger by mmap'ing a large file and
> using that as the buffer for fiemap.  This test adds a c program to do
> this, and the fstest creates a large enough file and then runs the
> reproducer on the file.  Without the fix btrfs deadlocks, with the fix
> we pass fine.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
> v2->v3:
> - Add fiemap-fault to .gitignore
> - Added a _cleanup() helper
> - Just let the output of fiemap-fault go instead of using || _fail
> - Added the munmap
> - Moved $dst to $TEST_DIR/$seq

looks good.

Reviewed-by: Anand Jain <anand.jain@oracle.com>

A minor whitespace error below, maybe Zorro can handle it when applied.

<snap>

> diff --git a/tests/generic/808 b/tests/generic/808
> new file mode 100755
> index 00000000..36015f35
> --- /dev/null
> +++ b/tests/generic/808
> @@ -0,0 +1,48 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
> +#
> +# FS QA Test 808
> +#
> +# Test fiemap into an mmaped buffer of the same file
> +#
> +# Create a reasonably large file, then run a program which mmaps it and uses
> +# that as a buffer for an fiemap call.  This is a regression test for btrfs
> +# where we used to hold a lock for the duration of the fiemap call which would
> +# result in a deadlock if we page faulted.
> +#
> +. ./common/preamble
> +_begin_fstest quick auto fiemap
> +[ $FSTYP == "btrfs" ] && \
> +	_fixed_by_kernel_commit b0ad381fa769 \
> +		"btrfs: fix deadlock with fiemap and extent locking"
> +
> +_cleanup()
> +{
> +	rm -f $dst
> +	cd /
> +	rm -r -f $tmp.*
> +}
> +
> +# real QA test starts here
> +_supported_fs generic
> +_require_test
> +_require_odirect
> +_require_test_program fiemap-fault
> +dst=$TEST_DIR/$seq/fiemap-fault
> +
> +mkdir -p $TEST_DIR/$seq
> +
> +echo "Silence is golden"
> +
> +for i in $(seq 0 2 1000)
> +do
> +	$XFS_IO_PROG -d -f -c "pwrite -q $((i * 4096)) 4096" $dst
> +done
> +
> +$here/src/fiemap-fault $dst
> +
> +# success, all done
> +status=$?
> +exit

> +

Applying: generic/808: add a regression test for fiemap into an mmap range
.git/rebase-apply/patch:177: new blank line at EOF.
+
warning: 1 line adds whitespace errors.

Thanks.
diff mbox series

Patch

diff --git a/.gitignore b/.gitignore
index 3b160209..f0fb72bd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -205,6 +205,7 @@  tags
 /src/vfs/mount-idmapped
 /src/log-writes/replay-log
 /src/perf/*.pyc
+/src/filemap-fault
 
 # Symlinked files
 /tests/generic/035.out
diff --git a/src/Makefile b/src/Makefile
index e7442487..ab98a06f 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -34,7 +34,7 @@  LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
 	fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail \
 	detached_mounts_propagation ext4_resize t_readdir_3 splice2pipe \
-	uuid_ioctl t_snapshot_deleted_subvolume
+	uuid_ioctl t_snapshot_deleted_subvolume fiemap-fault
 
 EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
 	      btrfs_crc32c_forged_name.py popdir.pl popattr.py \
diff --git a/src/fiemap-fault.c b/src/fiemap-fault.c
new file mode 100644
index 00000000..73260068
--- /dev/null
+++ b/src/fiemap-fault.c
@@ -0,0 +1,74 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
+ */
+
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/fiemap.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int prep_mmap_buffer(int fd, void **addr)
+{
+	struct stat st;
+	int ret;
+
+	ret = fstat(fd, &st);
+	if (ret)
+		err(1, "failed to stat %d", fd);
+
+	*addr = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+	if (*addr == MAP_FAILED)
+		err(1, "failed to mmap %d", fd);
+
+	return st.st_size;
+}
+
+int main(int argc, char *argv[])
+{
+	struct fiemap *fiemap;
+	size_t sz, last = 0;
+	void *buf = NULL;
+	int ret, fd;
+
+	if (argc != 2)
+		errx(1, "no in and out file name arguments given");
+
+	fd = open(argv[1], O_RDWR, 0666);
+	if (fd == -1)
+		err(1, "failed to open %s", argv[1]);
+
+	sz = prep_mmap_buffer(fd, &buf);
+
+	fiemap = (struct fiemap *)buf;
+	fiemap->fm_flags = 0;
+	fiemap->fm_extent_count = (sz - sizeof(struct fiemap)) /
+				  sizeof(struct fiemap_extent);
+
+	while (last < sz) {
+		int i;
+
+		fiemap->fm_start = last;
+		fiemap->fm_length = sz - last;
+
+		ret = ioctl(fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
+		if (ret < 0)
+			err(1, "fiemap failed %d", errno);
+		for (i = 0; i < fiemap->fm_mapped_extents; i++)
+		       last = fiemap->fm_extents[i].fe_logical +
+			       fiemap->fm_extents[i].fe_length;
+	}
+
+	munmap(buf, sz);
+	close(fd);
+	return 0;
+}
diff --git a/tests/generic/808 b/tests/generic/808
new file mode 100755
index 00000000..36015f35
--- /dev/null
+++ b/tests/generic/808
@@ -0,0 +1,48 @@ 
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2024 Meta Platforms, Inc.  All Rights Reserved.
+#
+# FS QA Test 808
+#
+# Test fiemap into an mmaped buffer of the same file
+#
+# Create a reasonably large file, then run a program which mmaps it and uses
+# that as a buffer for an fiemap call.  This is a regression test for btrfs
+# where we used to hold a lock for the duration of the fiemap call which would
+# result in a deadlock if we page faulted.
+#
+. ./common/preamble
+_begin_fstest quick auto fiemap
+[ $FSTYP == "btrfs" ] && \
+	_fixed_by_kernel_commit b0ad381fa769 \
+		"btrfs: fix deadlock with fiemap and extent locking"
+
+_cleanup()
+{
+	rm -f $dst
+	cd /
+	rm -r -f $tmp.*
+}
+
+# real QA test starts here
+_supported_fs generic
+_require_test
+_require_odirect
+_require_test_program fiemap-fault
+dst=$TEST_DIR/$seq/fiemap-fault
+
+mkdir -p $TEST_DIR/$seq
+
+echo "Silence is golden"
+
+for i in $(seq 0 2 1000)
+do
+	$XFS_IO_PROG -d -f -c "pwrite -q $((i * 4096)) 4096" $dst
+done
+
+$here/src/fiemap-fault $dst
+
+# success, all done
+status=$?
+exit
+
diff --git a/tests/generic/808.out b/tests/generic/808.out
new file mode 100644
index 00000000..88253428
--- /dev/null
+++ b/tests/generic/808.out
@@ -0,0 +1,2 @@ 
+QA output created by 808
+Silence is golden