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// SPDX-License-Identifier: GPL-2.0
/*
* This program tests for hugepage leaks after DIO writes to a file using a
* hugepage as the user buffer. During DIO, the user buffer is pinned and
* should be properly unpinned upon completion. This patch verifies that the
* kernel correctly unpins the buffer at DIO completion for both aligned and
* unaligned user buffer offsets (w.r.t page boundary), ensuring the hugepage
* is freed upon unmapping.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include "vm_util.h"
#include "kselftest.h"
#ifndef STATX_DIOALIGN
#define STATX_DIOALIGN 0x00002000U
#endif
static int get_dio_alignment(int fd)
{
struct statx stx;
int ret;
ret = syscall(__NR_statx, fd, "", AT_EMPTY_PATH, STATX_DIOALIGN, &stx);
if (ret < 0)
return -1;
/*
* If STATX_DIOALIGN is unsupported, assume no alignment
* constraint and let the test proceed.
*/
if (!(stx.stx_mask & STATX_DIOALIGN) || !stx.stx_dio_offset_align)
return 1;
return stx.stx_dio_offset_align;
}
static bool check_dio_alignment(unsigned int start_off,
unsigned int end_off, unsigned int align)
{
unsigned int writesize = end_off - start_off;
/*
* The kernel's DIO path checks that file offset, length, and
* buffer address are all multiples of dio_offset_align. When
* this test case's parameters don't satisfy that, the write
* would fail with -EINVAL before exercising the hugetlb unpin
* path, so skip.
*/
if (start_off % align != 0 || writesize % align != 0) {
ksft_test_result_skip("DIO align=%u incompatible with offset %u writesize %u\n",
align, start_off, writesize);
return false;
}
return true;
}
static void run_dio_using_hugetlb(int fd, unsigned int start_off,
unsigned int end_off, unsigned int align)
{
char *buffer = NULL;
char *orig_buffer = NULL;
size_t h_pagesize = 0;
size_t writesize;
int free_hpage_b = 0;
int free_hpage_a = 0;
const int mmap_flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB;
const int mmap_prot = PROT_READ | PROT_WRITE;
if (!check_dio_alignment(start_off, end_off, align))
return;
writesize = end_off - start_off;
/* Get the default huge page size */
h_pagesize = default_huge_page_size();
if (!h_pagesize)
ksft_exit_fail_msg("Unable to determine huge page size\n");
/* Reset file position since fd is shared across tests */
if (lseek(fd, 0, SEEK_SET) < 0)
ksft_exit_fail_perror("lseek failed\n");
/* Get the free huge pages before allocation */
free_hpage_b = get_free_hugepages();
if (free_hpage_b == 0) {
close(fd);
ksft_exit_skip("No free hugepage, exiting!\n");
}
/* Allocate a hugetlb page */
orig_buffer = mmap(NULL, h_pagesize, mmap_prot, mmap_flags, -1, 0);
if (orig_buffer == MAP_FAILED) {
close(fd);
ksft_exit_fail_perror("Error mapping memory\n");
}
buffer = orig_buffer;
buffer += start_off;
memset(buffer, 'A', writesize);
/* Write the buffer to the file */
if (write(fd, buffer, writesize) != (writesize)) {
munmap(orig_buffer, h_pagesize);
close(fd);
ksft_exit_fail_perror("Error writing to file\n");
}
/* unmap the huge page */
munmap(orig_buffer, h_pagesize);
/* Get the free huge pages after unmap*/
free_hpage_a = get_free_hugepages();
ksft_print_msg("No. Free pages before allocation : %d\n", free_hpage_b);
ksft_print_msg("No. Free pages after munmap : %d\n", free_hpage_a);
/*
* If the no. of free hugepages before allocation and after unmap does
* not match - that means there could still be a page which is pinned.
*/
ksft_test_result(free_hpage_a == free_hpage_b,
"free huge pages from %u-%u\n", start_off, end_off);
}
int main(void)
{
int fd, align;
const size_t pagesize = psize();
ksft_print_header();
/* Check if huge pages are free */
if (!get_free_hugepages())
ksft_exit_skip("No free hugepage, exiting\n");
fd = open("/tmp", O_TMPFILE | O_RDWR | O_DIRECT, 0664);
if (fd < 0)
ksft_exit_skip("Unable to allocate file: %s\n", strerror(errno));
align = get_dio_alignment(fd);
if (align < 0)
ksft_exit_skip("Unable to obtain DIO alignment: %s\n",
strerror(errno));
ksft_set_plan(4);
/* start and end is aligned to pagesize */
run_dio_using_hugetlb(fd, 0, (pagesize * 3), align);
/* start is aligned but end is not aligned */
run_dio_using_hugetlb(fd, 0, (pagesize * 3) - (pagesize / 2), align);
/* start is unaligned and end is aligned */
run_dio_using_hugetlb(fd, pagesize / 2, (pagesize * 3), align);
/* both start and end are unaligned */
run_dio_using_hugetlb(fd, pagesize / 2, (pagesize * 3) + (pagesize / 2), align);
close(fd);
ksft_finished();
}
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