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selftests: add selftests for cachestat
JIRA: https://issues.redhat.com/browse/RHEL-50302 commit 88537aa Author: Nhat Pham <nphamcs@gmail.com> Date: Tue May 2 18:36:08 2023 -0700 selftests: add selftests for cachestat Test cachestat on a newly created file, /dev/ files, /proc/ files and a directory. Also test on a shmem file (which can also be tested with huge pages since tmpfs supports huge pages). [colin.i.king@gmail.com: fix spelling mistake "trucate" -> "truncate"] Link: https://lkml.kernel.org/r/20230505110855.2493457-1-colin.i.king@gmail.com [mpe@ellerman.id.au: avoid excessive stack allocation] Link: https://lkml.kernel.org/r/877ctfa6yv.fsf@mail.lhotse Link: https://lkml.kernel.org/r/20230503013608.2431726-4-nphamcs@gmail.com Signed-off-by: Nhat Pham <nphamcs@gmail.com> Signed-off-by: Colin Ian King <colin.i.king@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Brian Foster <bfoster@redhat.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Colin Ian King <colin.i.king@gmail.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Eric Chanudet <echanude@redhat.com>
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‎MAINTAINERS‎

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@@ -4158,6 +4158,13 @@ S: Supported
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F: Documentation/filesystems/caching/cachefiles.rst
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F: fs/cachefiles/
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CACHESTAT: PAGE CACHE STATS FOR A FILE
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M: Nhat Pham <nphamcs@gmail.com>
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M: Johannes Weiner <hannes@cmpxchg.org>
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L: linux-mm@kvack.org
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S: Maintained
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F: tools/testing/selftests/cachestat/test_cachestat.c
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CADENCE MIPI-CSI2 BRIDGES
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M: Maxime Ripard <mripard@kernel.org>
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L: linux-media@vger.kernel.org

‎tools/testing/selftests/Makefile‎

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TARGETS = arm64
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TARGETS += bpf
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TARGETS += breakpoints
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TARGETS += cachestat
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TARGETS += capabilities
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TARGETS += cgroup
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TARGETS += clone3

‎tools/testing/selftests/cachestat/.gitignore‎

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# SPDX-License-Identifier: GPL-2.0-only
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test_cachestat

‎tools/testing/selftests/cachestat/Makefile‎

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# SPDX-License-Identifier: GPL-2.0
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TEST_GEN_PROGS := test_cachestat
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CFLAGS += $(KHDR_INCLUDES)
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CFLAGS += -Wall
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CFLAGS += -lrt
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include ../lib.mk

‎tools/testing/selftests/cachestat/test_cachestat.c‎

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// SPDX-License-Identifier: GPL-2.0
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdbool.h>
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#include <linux/kernel.h>
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#include <linux/mman.h>
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#include <sys/mman.h>
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#include <sys/shm.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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#include <string.h>
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#include <fcntl.h>
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#include <errno.h>
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#include "../kselftest.h"
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static const char * const dev_files[] = {
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"/dev/zero", "/dev/null", "/dev/urandom",
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"/proc/version", "/proc"
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};
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static const int cachestat_nr = 451;
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void print_cachestat(struct cachestat *cs)
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{
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ksft_print_msg(
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"Using cachestat: Cached: %lu, Dirty: %lu, Writeback: %lu, Evicted: %lu, Recently Evicted: %lu\n",
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cs->nr_cache, cs->nr_dirty, cs->nr_writeback,
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cs->nr_evicted, cs->nr_recently_evicted);
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}
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bool write_exactly(int fd, size_t filesize)
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{
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int random_fd = open("/dev/urandom", O_RDONLY);
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char *cursor, *data;
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int remained;
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bool ret;
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if (random_fd < 0) {
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ksft_print_msg("Unable to access urandom.\n");
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ret = false;
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goto out;
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}
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data = malloc(filesize);
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if (!data) {
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ksft_print_msg("Unable to allocate data.\n");
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ret = false;
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goto close_random_fd;
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}
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remained = filesize;
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cursor = data;
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while (remained) {
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ssize_t read_len = read(random_fd, cursor, remained);
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if (read_len <= 0) {
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ksft_print_msg("Unable to read from urandom.\n");
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ret = false;
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goto out_free_data;
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}
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remained -= read_len;
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cursor += read_len;
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}
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/* write random data to fd */
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remained = filesize;
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cursor = data;
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while (remained) {
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ssize_t write_len = write(fd, cursor, remained);
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if (write_len <= 0) {
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ksft_print_msg("Unable write random data to file.\n");
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ret = false;
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goto out_free_data;
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}
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remained -= write_len;
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cursor += write_len;
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}
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ret = true;
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out_free_data:
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free(data);
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close_random_fd:
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close(random_fd);
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out:
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return ret;
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}
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/*
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* Open/create the file at filename, (optionally) write random data to it
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* (exactly num_pages), then test the cachestat syscall on this file.
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*
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* If test_fsync == true, fsync the file, then check the number of dirty
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* pages.
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*/
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bool test_cachestat(const char *filename, bool write_random, bool create,
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bool test_fsync, unsigned long num_pages, int open_flags,
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mode_t open_mode)
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{
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size_t PS = sysconf(_SC_PAGESIZE);
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int filesize = num_pages * PS;
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bool ret = true;
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long syscall_ret;
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struct cachestat cs;
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struct cachestat_range cs_range = { 0, filesize };
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int fd = open(filename, open_flags, open_mode);
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if (fd == -1) {
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ksft_print_msg("Unable to create/open file.\n");
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ret = false;
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goto out;
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} else {
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ksft_print_msg("Create/open %s\n", filename);
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}
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if (write_random) {
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if (!write_exactly(fd, filesize)) {
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ksft_print_msg("Unable to access urandom.\n");
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ret = false;
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goto out1;
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}
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}
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syscall_ret = syscall(cachestat_nr, fd, &cs_range, &cs, 0);
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ksft_print_msg("Cachestat call returned %ld\n", syscall_ret);
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if (syscall_ret) {
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ksft_print_msg("Cachestat returned non-zero.\n");
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ret = false;
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goto out1;
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} else {
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print_cachestat(&cs);
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if (write_random) {
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if (cs.nr_cache + cs.nr_evicted != num_pages) {
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ksft_print_msg(
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"Total number of cached and evicted pages is off.\n");
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ret = false;
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}
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}
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}
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if (test_fsync) {
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if (fsync(fd)) {
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ksft_print_msg("fsync fails.\n");
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ret = false;
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} else {
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syscall_ret = syscall(cachestat_nr, fd, &cs_range, &cs, 0);
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ksft_print_msg("Cachestat call (after fsync) returned %ld\n",
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syscall_ret);
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if (!syscall_ret) {
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print_cachestat(&cs);
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if (cs.nr_dirty) {
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ret = false;
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ksft_print_msg(
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"Number of dirty should be zero after fsync.\n");
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}
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} else {
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ksft_print_msg("Cachestat (after fsync) returned non-zero.\n");
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ret = false;
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goto out1;
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}
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}
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}
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out1:
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close(fd);
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if (create)
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remove(filename);
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out:
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return ret;
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}
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bool test_cachestat_shmem(void)
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{
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size_t PS = sysconf(_SC_PAGESIZE);
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size_t filesize = PS * 512 * 2; /* 2 2MB huge pages */
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int syscall_ret;
190+
size_t compute_len = PS * 512;
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struct cachestat_range cs_range = { PS, compute_len };
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char *filename = "tmpshmcstat";
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struct cachestat cs;
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bool ret = true;
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unsigned long num_pages = compute_len / PS;
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int fd = shm_open(filename, O_CREAT | O_RDWR, 0600);
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if (fd < 0) {
199+
ksft_print_msg("Unable to create shmem file.\n");
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ret = false;
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goto out;
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}
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204+
if (ftruncate(fd, filesize)) {
205+
ksft_print_msg("Unable to truncate shmem file.\n");
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ret = false;
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goto close_fd;
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}
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210+
if (!write_exactly(fd, filesize)) {
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ksft_print_msg("Unable to write to shmem file.\n");
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ret = false;
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goto close_fd;
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}
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syscall_ret = syscall(cachestat_nr, fd, &cs_range, &cs, 0);
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218+
if (syscall_ret) {
219+
ksft_print_msg("Cachestat returned non-zero.\n");
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ret = false;
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goto close_fd;
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} else {
223+
print_cachestat(&cs);
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if (cs.nr_cache + cs.nr_evicted != num_pages) {
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ksft_print_msg(
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"Total number of cached and evicted pages is off.\n");
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ret = false;
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}
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}
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close_fd:
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shm_unlink(filename);
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out:
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return ret;
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}
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int main(void)
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{
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int ret = 0;
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for (int i = 0; i < 5; i++) {
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const char *dev_filename = dev_files[i];
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if (test_cachestat(dev_filename, false, false, false,
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4, O_RDONLY, 0400))
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ksft_test_result_pass("cachestat works with %s\n", dev_filename);
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else {
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ksft_test_result_fail("cachestat fails with %s\n", dev_filename);
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ret = 1;
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}
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}
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if (test_cachestat("tmpfilecachestat", true, true,
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true, 4, O_CREAT | O_RDWR, 0400 | 0600))
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ksft_test_result_pass("cachestat works with a normal file\n");
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else {
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ksft_test_result_fail("cachestat fails with normal file\n");
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ret = 1;
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}
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if (test_cachestat_shmem())
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ksft_test_result_pass("cachestat works with a shmem file\n");
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else {
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ksft_test_result_fail("cachestat fails with a shmem file\n");
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ret = 1;
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}
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return ret;
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}

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