On Wed, Nov 11, 2020 at 03:40:03PM -0500, Zi Yan wrote:
> From: Zi Yan <ziy@xxxxxxxxxx>
>
> Huge pages in the process with the given pid and virtual address range
> are split. It is used to test split huge page function. In addition,
> a testing program is added to tools/testing/selftests/vm to utilize the
> interface by splitting PMD THPs.
>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> ---
> mm/huge_memory.c | 98 +++++++++++
> mm/internal.h | 1 +
> mm/migrate.c | 2 +-
> tools/testing/selftests/vm/Makefile | 1 +
> .../selftests/vm/split_huge_page_test.c | 161 ++++++++++++++++++
> 5 files changed, 262 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/vm/split_huge_page_test.c
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 207ebca8c654..c4fead5ead31 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -7,6 +7,7 @@
>
> #include <linux/mm.h>
> #include <linux/sched.h>
> +#include <linux/sched/mm.h>
> #include <linux/sched/coredump.h>
> #include <linux/sched/numa_balancing.h>
> #include <linux/highmem.h>
> @@ -2935,10 +2936,107 @@ static int split_huge_pages_set(void *data, u64 val)
> DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
> "%llu\n");
>
> +static ssize_t split_huge_pages_in_range_pid_write(struct file *file,
> + const char __user *buf, size_t count, loff_t *ppops)
> +{
> + static DEFINE_MUTEX(mutex);
> + ssize_t ret;
> + char input_buf[80]; /* hold pid, start_vaddr, end_vaddr */
> + int pid;
> + unsigned long vaddr_start, vaddr_end, addr;
> + nodemask_t task_nodes;
> + struct mm_struct *mm;
> +
> + ret = mutex_lock_interruptible(&mutex);
> + if (ret)
> + return ret;
> +
> + ret = -EFAULT;
> +
> + memset(input_buf, 0, 80);
> + if (copy_from_user(input_buf, buf, min_t(size_t, count, 80)))
> + goto out;
> +
> + input_buf[80] = '\0';
Hm. Out-of-buffer access?
> + ret = sscanf(input_buf, "%d,%lx,%lx", &pid, &vaddr_start, &vaddr_end);
Why hex without 0x prefix?
> + if (ret != 3) {
> + ret = -EINVAL;
> + goto out;
> + }
> + vaddr_start &= PAGE_MASK;
> + vaddr_end &= PAGE_MASK;
> +
> + ret = strlen(input_buf);
> + pr_debug("split huge pages in pid: %d, vaddr: [%lx - %lx]\n",
> + pid, vaddr_start, vaddr_end);
> +
> + mm = find_mm_struct(pid, &task_nodes);
I don't follow why you need nodemask.
> + if (IS_ERR(mm)) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + mmap_read_lock(mm);
> + for (addr = vaddr_start; addr < vaddr_end;) {
> + struct vm_area_struct *vma = find_vma(mm, addr);
> + unsigned int follflags;
> + struct page *page;
> +
> + if (!vma || addr < vma->vm_start || !vma_migratable(vma))
> + break;
> +
> + /* FOLL_DUMP to ignore special (like zero) pages */
> + follflags = FOLL_GET | FOLL_DUMP;
> + page = follow_page(vma, addr, follflags);
> +
> + if (IS_ERR(page))
> + break;
> + if (!page)
> + break;
> +
> + if (!is_transparent_hugepage(page))
> + goto next;
> +
> + if (!can_split_huge_page(page, NULL))
> + goto next;
> +
> + if (!trylock_page(page))
> + goto next;
> +
> + addr += page_size(page) - PAGE_SIZE;
Who said it was mapped as huge? mremap() allows to construct an PTE page
table that filled with PTE-mapped THPs, each of them distinct.
> +
> + /* reset addr if split fails */
> + if (split_huge_page(page))
> + addr -= (page_size(page) - PAGE_SIZE);
> +
> + unlock_page(page);
> +next:
> + /* next page */
> + addr += page_size(page);
Isn't it the second time if split_huge_page() succeed.
> + put_page(page);
> + }
> + mmap_read_unlock(mm);
> +
> +
> + mmput(mm);
> +out:
> + mutex_unlock(&mutex);
> + return ret;
> +
> +}
> +
> +static const struct file_operations split_huge_pages_in_range_pid_fops = {
> + .owner = THIS_MODULE,
> + .write = split_huge_pages_in_range_pid_write,
> + .llseek = no_llseek,
> +};
> +
> static int __init split_huge_pages_debugfs(void)
> {
> debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
> &split_huge_pages_fops);
> + debugfs_create_file("split_huge_pages_in_range_pid", 0200, NULL, NULL,
> + &split_huge_pages_in_range_pid_fops);
> return 0;
> }
> late_initcall(split_huge_pages_debugfs);
> diff --git a/mm/internal.h b/mm/internal.h
> index 3ea43642b99d..fd841a38830f 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -624,4 +624,5 @@ struct migration_target_control {
>
> bool truncate_inode_partial_page(struct page *page, loff_t start, loff_t end);
> void page_cache_free_page(struct address_space *mapping, struct page *page);
> +struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes);
> #endif /* __MM_INTERNAL_H */
> diff --git a/mm/migrate.c b/mm/migrate.c
> index a50bbb0e029b..e35654d1087d 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1851,7 +1851,7 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
> return nr_pages ? -EFAULT : 0;
> }
>
> -static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
> +struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
> {
> struct task_struct *task;
> struct mm_struct *mm;
> diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
> index 62fb15f286ee..d9ead0cdd3e9 100644
> --- a/tools/testing/selftests/vm/Makefile
> +++ b/tools/testing/selftests/vm/Makefile
> @@ -42,6 +42,7 @@ TEST_GEN_FILES += on-fault-limit
> TEST_GEN_FILES += thuge-gen
> TEST_GEN_FILES += transhuge-stress
> TEST_GEN_FILES += userfaultfd
> +TEST_GEN_FILES += split_huge_page_test
>
> ifeq ($(ARCH),x86_64)
> CAN_BUILD_I386 := $(shell ./../x86/check_cc.sh $(CC) ../x86/trivial_32bit_program.c -m32)
> diff --git a/tools/testing/selftests/vm/split_huge_page_test.c b/tools/testing/selftests/vm/split_huge_page_test.c
> new file mode 100644
> index 000000000000..c8a32ae9e13a
> --- /dev/null
> +++ b/tools/testing/selftests/vm/split_huge_page_test.c
> @@ -0,0 +1,161 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include "numa.h"
> +#include <unistd.h>
> +#include <errno.h>
> +#include <inttypes.h>
> +#include <string.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <sys/mman.h>
> +#include <sys/time.h>
> +#include <sys/wait.h>
> +#include <malloc.h>
> +#include <stdbool.h>
> +
> +#define PAGE_4KB (4096UL)
> +#define PAGE_2MB (512UL*PAGE_4KB)
> +#define PAGE_1GB (512UL*PAGE_2MB)
> +
> +#define PRESENT_MASK (1UL<<63)
> +#define SWAPPED_MASK (1UL<<62)
> +#define PAGE_TYPE_MASK (1UL<<61)
> +#define PFN_MASK ((1UL<<55)-1)
> +
> +#define KPF_THP (1UL<<22)
> +#define KPF_PUD_THP (1UL<<27)
> +
> +#define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages_in_range_pid"
> +#define SMAP_PATH "/proc/self/smaps"
> +#define INPUT_MAX 80
> +
> +static int write_file(const char *path, const char *buf, size_t buflen)
> +{
> + int fd;
> + ssize_t numwritten;
> +
> + fd = open(path, O_WRONLY);
> + if (fd == -1)
> + return 0;
> +
> + numwritten = write(fd, buf, buflen - 1);
> + close(fd);
> + if (numwritten < 1)
> + return 0;
> +
> + return (unsigned int) numwritten;
> +}
> +
> +static void write_debugfs(int pid, uint64_t vaddr_start, uint64_t vaddr_end)
> +{
> + char input[INPUT_MAX];
> + int ret;
> +
> + ret = snprintf(input, INPUT_MAX, "%d,%lx,%lx", pid, vaddr_start,
> + vaddr_end);
> + if (ret >= INPUT_MAX) {
> + printf("%s: Debugfs input is too long\n", __func__);
> + exit(EXIT_FAILURE);
> + }
> +
> + if (!write_file(SPLIT_DEBUGFS, input, ret + 1)) {
> + perror(SPLIT_DEBUGFS);
> + exit(EXIT_FAILURE);
> + }
> +}
> +
> +#define MAX_LINE_LENGTH 500
> +
> +static bool check_for_pattern(FILE *fp, char *pattern, char *buf)
> +{
> + while (fgets(buf, MAX_LINE_LENGTH, fp) != NULL) {
> + if (!strncmp(buf, pattern, strlen(pattern)))
> + return true;
> + }
> + return false;
> +}
> +
> +static uint64_t check_huge(void *addr)
> +{
> + uint64_t thp = 0;
> + int ret;
> + FILE *fp;
> + char buffer[MAX_LINE_LENGTH];
> + char addr_pattern[MAX_LINE_LENGTH];
> +
> + ret = snprintf(addr_pattern, MAX_LINE_LENGTH, "%08lx-",
> + (unsigned long) addr);
> + if (ret >= MAX_LINE_LENGTH) {
> + printf("%s: Pattern is too long\n", __func__);
> + exit(EXIT_FAILURE);
> + }
> +
> +
> + fp = fopen(SMAP_PATH, "r");
> + if (!fp) {
> + printf("%s: Failed to open file %s\n", __func__, SMAP_PATH);
> + exit(EXIT_FAILURE);
> + }
> + if (!check_for_pattern(fp, addr_pattern, buffer))
> + goto err_out;
> +
> + /*
> + * Fetch the AnonHugePages: in the same block and check the number of
> + * hugepages.
> + */
> + if (!check_for_pattern(fp, "AnonHugePages:", buffer))
> + goto err_out;
> +
> + if (sscanf(buffer, "AnonHugePages:%10ld kB", &thp) != 1) {
> + printf("Reading smap error\n");
> + exit(EXIT_FAILURE);
> + }
> +
> +err_out:
> + fclose(fp);
> + return thp;
> +}
> +
> +void split_pmd_thp(void)
> +{
> + char *one_page;
> + size_t len = 4 * PAGE_2MB;
> + uint64_t thp_size;
> +
> + one_page = memalign(PAGE_1GB, len);
> +
> + madvise(one_page, len, MADV_HUGEPAGE);
> +
> + memset(one_page, 1, len);
> +
> + thp_size = check_huge(one_page);
> + if (!thp_size) {
> + printf("No THP is allocatd");
> + exit(EXIT_FAILURE);
> + }
> +
> + /* split all possible huge pages */
> + write_debugfs(getpid(), (uint64_t)one_page, (uint64_t)one_page + len);
> +
> + *one_page = 0;
> +
> + thp_size = check_huge(one_page);
> + if (thp_size) {
> + printf("Still %ld kB AnonHugePages not split\n", thp_size);
> + exit(EXIT_FAILURE);
> + }
> +
> + printf("Split huge pages successful\n");
> + free(one_page);
> +}
> +
> +int main(int argc, char **argv)
> +{
> + split_pmd_thp();
> +
> + return 0;
> +}
> --
> 2.28.0
>
>
--
Kirill A. Shutemov
