Re: [PATCH 08/10] generic: test file writers racing with FIDEDUPERANGE

Chandan Babu R
2021-03-12T07:13:59Z

On 09 Mar 2021 at 10:10, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
>
> Create a test to make sure that dedupe actually locks the file ranges
> correctly before starting the content comparison and keeps them locked
> until the operation completes.
>

Looks good to me.

Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>

> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
> src/Makefile | 2
> src/deduperace.c | 370 +++++++++++++++++++++++++++++++++++++++++++++++++
> tests/generic/949 | 51 +++++++
> tests/generic/949.out | 2
> tests/generic/group | 1
> 5 files changed, 425 insertions(+), 1 deletion(-)
> create mode 100644 src/deduperace.c
> create mode 100755 tests/generic/949
> create mode 100644 tests/generic/949.out
>
>
> diff --git a/src/Makefile b/src/Makefile
> index 811b24e4..38ee6718 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -21,7 +21,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \
>
> LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
> preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \
> - locktest unwritten_mmap bulkstat_unlink_test \
> + locktest unwritten_mmap bulkstat_unlink_test deduperace \
> bulkstat_unlink_test_modified t_dir_offset t_futimens t_immutable \
> stale_handle pwrite_mmap_blocked t_dir_offset2 seek_sanity_test \
> seek_copy_test t_readdir_1 t_readdir_2 fsync-tester nsexec cloner \
> diff --git a/src/deduperace.c b/src/deduperace.c
> new file mode 100644
> index 00000000..b252d436
> --- /dev/null
> +++ b/src/deduperace.c
> @@ -0,0 +1,370 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2021 Oracle. All Rights Reserved.
> + * Author: Darrick J. Wong <djwong@kernel.org>
> + *
> + * Race pwrite/mwrite with dedupe to see if we got the locking right.
> + *
> + * File writes and mmap writes should not be able to change the src_fd's
> + * contents after dedupe prep has verified that the file contents are the same.
> + */
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <sys/mman.h>
> +#include <sys/ioctl.h>
> +#include <linux/fs.h>
> +#include <string.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <pthread.h>
> +#include <stdlib.h>
> +#include <errno.h>
> +
> +#define GOOD_BYTE 0x58
> +#define BAD_BYTE 0x66
> +
> +#ifndef FIDEDUPERANGE
> +/* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
> +#define FILE_DEDUPE_RANGE_SAME 0
> +#define FILE_DEDUPE_RANGE_DIFFERS 1
> +
> +/* from struct btrfs_ioctl_file_extent_same_info */
> +struct file_dedupe_range_info {
> + __s64 dest_fd; /* in - destination file */
> + __u64 dest_offset; /* in - start of extent in destination */
> + __u64 bytes_deduped; /* out - total # of bytes we were able
> + * to dedupe from this file. */
> + /* status of this dedupe operation:
> + * < 0 for error
> + * == FILE_DEDUPE_RANGE_SAME if dedupe succeeds
> + * == FILE_DEDUPE_RANGE_DIFFERS if data differs
> + */
> + __s32 status; /* out - see above description */
> + __u32 reserved; /* must be zero */
> +};
> +
> +/* from struct btrfs_ioctl_file_extent_same_args */
> +struct file_dedupe_range {
> + __u64 src_offset; /* in - start of extent in source */
> + __u64 src_length; /* in - length of extent */
> + __u16 dest_count; /* in - total elements in info array */
> + __u16 reserved1; /* must be zero */
> + __u32 reserved2; /* must be zero */
> + struct file_dedupe_range_info info[0];
> +};
> +#define FIDEDUPERANGE _IOWR(0x94, 54, struct file_dedupe_range)
> +#endif /* FIDEDUPERANGE */
> +
> +static int fd1, fd2;
> +static loff_t offset = 37; /* Nice low offset to trick the compare */
> +static loff_t blksz;
> +
> +/* Continuously dirty the pagecache for the region being dupe-tested. */
> +void *
> +mwriter(
> + void *data)
> +{
> + volatile char *p;
> +
> + p = mmap(NULL, blksz, PROT_WRITE, MAP_SHARED, fd1, 0);
> + if (p == MAP_FAILED) {
> + perror("mmap");
> + exit(2);
> + }
> +
> + while (1) {
> + *(p + offset) = BAD_BYTE;
> + *(p + offset) = GOOD_BYTE;
> + }
> +}
> +
> +/* Continuously write to the region being dupe-tested. */
> +void *
> +pwriter(
> + void *data)
> +{
> + char v;
> + ssize_t sz;
> +
> + while (1) {
> + v = BAD_BYTE;
> + sz = pwrite(fd1, &v, sizeof(v), offset);
> + if (sz != sizeof(v)) {
> + perror("pwrite0");
> + exit(2);
> + }
> +
> + v = GOOD_BYTE;
> + sz = pwrite(fd1, &v, sizeof(v), offset);
> + if (sz != sizeof(v)) {
> + perror("pwrite1");
> + exit(2);
> + }
> + }
> +
> + return NULL;
> +}
> +
> +static inline void
> +complain(
> + loff_t offset,
> + char bad)
> +{
> + fprintf(stderr, "ASSERT: offset %llu should be 0x%x, got 0x%x!\n",
> + (unsigned long long)offset, GOOD_BYTE, bad);
> + abort();
> +}
> +
> +/* Make sure the destination file pagecache never changes. */
> +void *
> +mreader(
> + void *data)
> +{
> + volatile char *p;
> +
> + p = mmap(NULL, blksz, PROT_READ, MAP_SHARED, fd2, 0);
> + if (p == MAP_FAILED) {
> + perror("mmap");
> + exit(2);
> + }
> +
> + while (1) {
> + if (*(p + offset) != GOOD_BYTE)
> + complain(offset, *(p + offset));
> + }
> +}
> +
> +/* Make sure the destination file never changes. */
> +void *
> +preader(
> + void *data)
> +{
> + char v;
> + ssize_t sz;
> +
> + while (1) {
> + sz = pread(fd2, &v, sizeof(v), offset);
> + if (sz != sizeof(v)) {
> + perror("pwrite0");
> + exit(2);
> + }
> +
> + if (v != GOOD_BYTE)
> + complain(offset, v);
> + }
> +
> + return NULL;
> +}
> +
> +void
> +print_help(const char *progname)
> +{
> + printf("Usage: %s [-b blksz] [-c dir] [-n nr_ops] [-o offset] [-r] [-w] [-v]\n",
> + progname);
> + printf("-b sets the block size (default is autoconfigured)\n");
> + printf("-c chdir to this path before starting\n");
> + printf("-n controls the number of dedupe ops (default 10000)\n");
> + printf("-o reads and writes to this offset (default 37)\n");
> + printf("-r uses pread instead of mmap read.\n");
> + printf("-v prints status updates.\n");
> + printf("-w uses pwrite instead of mmap write.\n");
> +}
> +
> +int
> +main(
> + int argc,
> + char *argv[])
> +{
> + struct file_dedupe_range *fdr;
> + char *Xbuf;
> + void *(*reader_fn)(void *) = mreader;
> + void *(*writer_fn)(void *) = mwriter;
> + unsigned long same = 0;
> + unsigned long differs = 0;
> + unsigned long i, nr_ops = 10000;
> + ssize_t sz;
> + pthread_t reader, writer;
> + int verbose = 0;
> + int c;
> + int ret;
> +
> + while ((c = getopt(argc, argv, "b:c:n:o:rvw")) != -1) {
> + switch (c) {
> + case 'b':
> + errno = 0;
> + blksz = strtoul(optarg, NULL, 0);
> + if (errno) {
> + perror(optarg);
> + exit(1);
> + }
> + break;
> + case 'c':
> + ret = chdir(optarg);
> + if (ret) {
> + perror("chdir");
> + exit(1);
> + }
> + break;
> + case 'n':
> + errno = 0;
> + nr_ops = strtoul(optarg, NULL, 0);
> + if (errno) {
> + perror(optarg);
> + exit(1);
> + }
> + break;
> + case 'o':
> + errno = 0;
> + offset = strtoul(optarg, NULL, 0);
> + if (errno) {
> + perror(optarg);
> + exit(1);
> + }
> + break;
> + case 'r':
> + reader_fn = preader;
> + break;
> + case 'v':
> + verbose = 1;
> + break;
> + case 'w':
> + writer_fn = pwriter;
> + break;
> + default:
> + print_help(argv[0]);
> + exit(1);
> + break;
> + }
> + }
> +
> + fdr = malloc(sizeof(struct file_dedupe_range) +
> + sizeof(struct file_dedupe_range_info));
> + if (!fdr) {
> + perror("malloc");
> + exit(1);
> + }
> +
> + /* Initialize both files. */
> + fd1 = open("file1", O_RDWR | O_CREAT | O_TRUNC | O_NOATIME, 0600);
> + if (fd1 < 0) {
> + perror("file1");
> + exit(1);
> + }
> +
> + fd2 = open("file2", O_RDWR | O_CREAT | O_TRUNC | O_NOATIME, 0600);
> + if (fd2 < 0) {
> + perror("file2");
> + exit(1);
> + }
> +
> + if (blksz <= 0) {
> + struct stat statbuf;
> +
> + ret = fstat(fd1, &statbuf);
> + if (ret) {
> + perror("file1 stat");
> + exit(1);
> + }
> + blksz = statbuf.st_blksize;
> + }
> +
> + if (offset >= blksz) {
> + fprintf(stderr, "offset (%llu) < blksz (%llu)?\n",
> + (unsigned long long)offset,
> + (unsigned long long)blksz);
> + exit(1);
> + }
> +
> + Xbuf = malloc(blksz);
> + if (!Xbuf) {
> + perror("malloc buffer");
> + exit(1);
> + }
> + memset(Xbuf, GOOD_BYTE, blksz);
> +
> + sz = pwrite(fd1, Xbuf, blksz, 0);
> + if (sz != blksz) {
> + perror("file1 write");
> + exit(1);
> + }
> +
> + sz = pwrite(fd2, Xbuf, blksz, 0);
> + if (sz != blksz) {
> + perror("file2 write");
> + exit(1);
> + }
> +
> + ret = fsync(fd1);
> + if (ret) {
> + perror("file1 fsync");
> + exit(1);
> + }
> +
> + ret = fsync(fd2);
> + if (ret) {
> + perror("file2 fsync");
> + exit(1);
> + }
> +
> + /* Start our reader and writer threads. */
> + ret = pthread_create(&reader, NULL, reader_fn, NULL);
> + if (ret) {
> + fprintf(stderr, "rthread: %s\n", strerror(ret));
> + exit(1);
> + }
> +
> + ret = pthread_create(&writer, NULL, writer_fn, NULL);
> + if (ret) {
> + fprintf(stderr, "wthread: %s\n", strerror(ret));
> + exit(1);
> + }
> +
> + /*
> + * Now start deduping. If the contents match, fd1's blocks will be
> + * remapped into fd2, which is why the writer thread targets fd1 and
> + * the reader checks fd2 to make sure that none of fd1's writes ever
> + * make it into fd2.
> + */
> + for (i = 1; i <= nr_ops; i++) {
> + fdr->src_offset = 0;
> + fdr->src_length = blksz;
> + fdr->dest_count = 1;
> + fdr->reserved1 = 0;
> + fdr->reserved2 = 0;
> + fdr->info[0].dest_fd = fd2;
> + fdr->info[0].dest_offset = 0;
> + fdr->info[0].reserved = 0;
> +
> + ret = ioctl(fd1, FIDEDUPERANGE, fdr);
> + if (ret) {
> + perror("dedupe");
> + exit(2);
> + }
> +
> + switch (fdr->info[0].status) {
> + case FILE_DEDUPE_RANGE_DIFFERS:
> + differs++;
> + break;
> + case FILE_DEDUPE_RANGE_SAME:
> + same++;
> + break;
> + default:
> + fprintf(stderr, "deduperange: %s\n",
> + strerror(-fdr->info[0].status));
> + exit(2);
> + break;
> + }
> +
> + if (verbose && (i % 337) == 0)
> + printf("nr_ops: %lu; same: %lu; differs: %lu\n",
> + i, same, differs);
> + }
> +
> + if (verbose)
> + printf("nr_ops: %lu; same: %lu; differs: %lu\n", i - 1, same,
> + differs);
> +
> + /* Program termination will kill the threads and close the files. */
> + return 0;
> +}
> diff --git a/tests/generic/949 b/tests/generic/949
> new file mode 100755
> index 00000000..3951490b
> --- /dev/null
> +++ b/tests/generic/949
> @@ -0,0 +1,51 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +# Copyright (c) 2021 Oracle. All Rights Reserved.
> +#
> +# FS QA Test No. 949
> +#
> +# Make sure that mmap and file writers racing with FIDEDUPERANGE cannot write
> +# to the file after the dedupe prep function has decided that the file contents
> +# are identical and we can therefore go ahead with the remapping.
> +
> +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/reflink
> +
> +# real QA test starts here
> +_supported_fs generic
> +_require_scratch_dedupe
> +
> +rm -f $seqres.full
> +
> +nr_ops=$((TIME_FACTOR * 10000))
> +
> +# Format filesystem
> +_scratch_mkfs > $seqres.full
> +_scratch_mount
> +
> +# Test once with mmap writes
> +$here/src/deduperace -c $SCRATCH_MNT -n $nr_ops
> +
> +# Test again with pwrites for the lulz
> +$here/src/deduperace -c $SCRATCH_MNT -n $nr_ops -w
> +
> +echo Silence is golden.
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/generic/949.out b/tests/generic/949.out
> new file mode 100644
> index 00000000..2998b46c
> --- /dev/null
> +++ b/tests/generic/949.out
> @@ -0,0 +1,2 @@
> +QA output created by 949
> +Silence is golden.
> diff --git a/tests/generic/group b/tests/generic/group
> index d5cfdd51..778aa8c4 100644
> --- a/tests/generic/group
> +++ b/tests/generic/group
> @@ -630,3 +630,4 @@
> 625 auto quick verity
> 947 auto quick rw clone
> 948 auto quick rw copy_range
> +949 auto quick rw dedupe clone

--
chandan