selftests/mm: extract read_sysfs and write_sysfs into vm_util

Extract read_sysfs and write_sysfs into vm_util.  Meanwhile, rename the
function in thuge-gen that has the same name as read_sysfs.

Link: https://lkml.kernel.org/r/20250529155650.4017699-4-pulehui@huaweicloud.com
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Pu Lehui

tools/testing/selftests/mm/ksm_tests.c

@@ -58,40 +58,12 @@ int debug;
 
 static int ksm_write_sysfs(const char *file_path, unsigned long val)
 {
-	FILE *f = fopen(file_path, "w");
-
-	if (!f) {
-		fprintf(stderr, "f %s\n", file_path);
-		perror("fopen");
-		return 1;
-	}
-	if (fprintf(f, "%lu", val) < 0) {
-		perror("fprintf");
-		fclose(f);
-		return 1;
-	}
-	fclose(f);
-
-	return 0;
+	return write_sysfs(file_path, val);
 }
 
 static int ksm_read_sysfs(const char *file_path, unsigned long *val)
 {
-	FILE *f = fopen(file_path, "r");
-
-	if (!f) {
-		fprintf(stderr, "f %s\n", file_path);
-		perror("fopen");
-		return 1;
-	}
-	if (fscanf(f, "%lu", val) != 1) {
-		perror("fscanf");
-		fclose(f);
-		return 1;
-	}
-	fclose(f);
-
-	return 0;
+	return read_sysfs(file_path, val);
 }
 
 static void ksm_print_sysfs(void)

tools/testing/selftests/mm/thuge-gen.c

@@ -77,7 +77,7 @@ void show(unsigned long ps)
 	system(buf);
 }
 
-unsigned long read_sysfs(int warn, char *fmt, ...)
+unsigned long thuge_read_sysfs(int warn, char *fmt, ...)
 {
 	char *line = NULL;
 	size_t linelen = 0;
@@ -106,7 +106,7 @@ unsigned long read_sysfs(int warn, char *fmt, ...)
 
 unsigned long read_free(unsigned long ps)
 {
-	return read_sysfs(ps != getpagesize(),
+	return thuge_read_sysfs(ps != getpagesize(),
 			  "/sys/kernel/mm/hugepages/hugepages-%lukB/free_hugepages",
 			  ps >> 10);
 }
@@ -195,7 +195,7 @@ void find_pagesizes(void)
 	}
 	globfree(&g);
 
-	if (read_sysfs(0, "/proc/sys/kernel/shmmax") < NUM_PAGES * largest)
+	if (thuge_read_sysfs(0, "/proc/sys/kernel/shmmax") < NUM_PAGES * largest)
 		ksft_exit_fail_msg("Please do echo %lu > /proc/sys/kernel/shmmax",
 				   largest * NUM_PAGES);
 

tools/testing/selftests/mm/vm_util.c

@@ -486,3 +486,41 @@ int close_procmap(struct procmap_fd *procmap)
 {
 	return close(procmap->fd);
 }
+
+int write_sysfs(const char *file_path, unsigned long val)
+{
+	FILE *f = fopen(file_path, "w");
+
+	if (!f) {
+		fprintf(stderr, "f %s\n", file_path);
+		perror("fopen");
+		return 1;
+	}
+	if (fprintf(f, "%lu", val) < 0) {
+		perror("fprintf");
+		fclose(f);
+		return 1;
+	}
+	fclose(f);
+
+	return 0;
+}
+
+int read_sysfs(const char *file_path, unsigned long *val)
+{
+	FILE *f = fopen(file_path, "r");
+
+	if (!f) {
+		fprintf(stderr, "f %s\n", file_path);
+		perror("fopen");
+		return 1;
+	}
+	if (fscanf(f, "%lu", val) != 1) {
+		perror("fscanf");
+		fclose(f);
+		return 1;
+	}
+	fclose(f);
+
+	return 0;
+}

tools/testing/selftests/mm/vm_util.h

@@ -88,6 +88,8 @@ int open_procmap(pid_t pid, struct procmap_fd *procmap_out);
 int query_procmap(struct procmap_fd *procmap);
 bool find_vma_procmap(struct procmap_fd *procmap, void *address);
 int close_procmap(struct procmap_fd *procmap);
+int write_sysfs(const char *file_path, unsigned long val);
+int read_sysfs(const char *file_path, unsigned long *val);
 
 static inline int open_self_procmap(struct procmap_fd *procmap_out)
 {