Some filesystems have problems when the buffer passed to read or write is memory-mapped to the file being read from or written to and the buffer is faulted in during the read or write. (That's probably not a recommended use case, but it should work nevertheless.) Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx> --- src/Makefile | 3 +- src/mmap-rw-fault.c | 110 ++++++++++++++++++++++++++++++++++++++++++ tests/generic/637 | 40 +++++++++++++++ tests/generic/637.out | 2 + tests/generic/group | 1 + 5 files changed, 155 insertions(+), 1 deletion(-) create mode 100644 src/mmap-rw-fault.c create mode 100755 tests/generic/637 create mode 100644 tests/generic/637.out diff --git a/src/Makefile b/src/Makefile index cc0b9579..13cdf19b 100644 --- a/src/Makefile +++ b/src/Makefile @@ -17,7 +17,8 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \ t_mmap_cow_race t_mmap_fallocate fsync-err t_mmap_write_ro \ t_ext4_dax_journal_corruption t_ext4_dax_inline_corruption \ t_ofd_locks t_mmap_collision mmap-write-concurrent \ - t_get_file_time t_create_short_dirs t_create_long_dirs t_enospc + t_get_file_time t_create_short_dirs t_create_long_dirs t_enospc \ + mmap-rw-fault 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/mmap-rw-fault.c b/src/mmap-rw-fault.c new file mode 100644 index 00000000..f721bf9f --- /dev/null +++ b/src/mmap-rw-fault.c @@ -0,0 +1,110 @@ +/* Trigger mmap page faults in the same file during pread and pwrite. */ + +#ifndef _GNU_SOURCE +#define _GNU_SOURCE /* to get definition of O_DIRECT flag. */ +#endif + +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/mman.h> +#include <fcntl.h> +#include <unistd.h> +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <errno.h> +#include <err.h> + +char *filename; +unsigned int page_size; +void *page; +char *addr; +int fd; +ssize_t ret; + +/* + * Leave a hole at the beginning of the test file and initialize a block of + * @page_size bytes at offset @page_size to @c. Then, reopen the file and + * mmap the first two pages. + */ +void init(char c) +{ + fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY | O_DIRECT, 0666); + if (fd == -1) + goto fail; + memset(page, c, page_size); + ret = pwrite(fd, page, page_size, page_size); + if (ret != page_size) + goto fail; + if (close(fd)) + goto fail; + + fd = open(filename, O_RDWR); + if (fd == -1) + goto fail; + addr = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0); + if (addr == MAP_FAILED) + err(1, NULL); + +fail: + err(1, "%s", filename); +} + +void done(void) +{ + if (fsync(fd)) + goto fail; + if (close(fd)) + goto fail; + return; + +fail: + err(1, "%s", filename); +} + +int main(int argc, char *argv[]) +{ + if (argc != 2) + errx(1, "no test filename argument given"); + filename = argv[1]; + + page_size = ret = sysconf(_SC_PAGE_SIZE); + if (ret == -1) + err(1, NULL); + + ret = posix_memalign(&page, page_size, page_size); + if (ret) { + errno = ENOMEM; + err(1, NULL); + } + + /* + * Make sure page faults during pread are handled correctly. + */ + init('x'); + ret = pread(fd, addr, page_size, page_size); + if (ret != page_size) + goto fail; + if (memcmp(addr, page, page_size)) + errx(1, "pread is broken"); + done(); + + /* + * Make sure page faults during pwrite are handled correctly. + */ + init('y'); + ret = pwrite(fd, addr + page_size, page_size, 0); + if (ret != page_size) + goto fail; + if (memcmp(addr, page, page_size)) + errx(1, "pwrite is broken"); + done(); + + if (unlink(filename)) + goto fail; + + return 0; + +fail: + err(1, "%s", filename); +} diff --git a/tests/generic/637 b/tests/generic/637 new file mode 100755 index 00000000..d3c3f235 --- /dev/null +++ b/tests/generic/637 @@ -0,0 +1,40 @@ +#! /bin/bash +# SPDX-License-Identifier: GPL-2.0 +# Copyright (c) 2021 Red Hat, Inc. All Rights Reserved. +# +# FS QA Test 637 +# +# Trigger mmap page faults in the same file during pread and pwrite +# +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 $tmp.* +} + +# get standard environment, filters and checks +. ./common/rc +. ./common/filter + +# real QA test starts here + +# Modify as appropriate. +_supported_fs generic +_require_test + +$here/src/mmap-rw-fault $TEST_DIR/mmap-rw-fault.tmp \ +|| exit + +# success, all done +echo "Silence is golden" +status=0 +exit diff --git a/tests/generic/637.out b/tests/generic/637.out new file mode 100644 index 00000000..55a3d825 --- /dev/null +++ b/tests/generic/637.out @@ -0,0 +1,2 @@ +QA output created by 637 +Silence is golden diff --git a/tests/generic/group b/tests/generic/group index 105763c4..01996b48 100644 --- a/tests/generic/group +++ b/tests/generic/group @@ -639,3 +639,4 @@ 634 auto quick atime bigtime 635 auto quick atime bigtime shutdown 636 auto quick swap +637 auto -- 2.26.3