+ tools-lib-mm-add-shared-file-helpers.patch added to mm-new branch

+ tools-lib-mm-add-shared-file-helpers.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: tools/lib/mm: add shared file helpers
has been added to the -mm mm-new branch.  Its filename is
     tools-lib-mm-add-shared-file-helpers.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tools-lib-mm-add-shared-file-helpers.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: Sarthak Sharma <sarthak.sharma@arm.com>
Subject: tools/lib/mm: add shared file helpers
Date: Fri, 4 Sep 2026 18:06:27 +0530

Move read_file(), write_file(), read_num(), write_num() and
write_num_ignore_einval() out of tools/testing/selftests/mm/vm_util.c into
a new shared helper under tools/lib/mm/.

These helpers are used by mm selftests today and will also be needed by
shared hugepage helpers in subsequent patches.  Move them to a generic
location so they can be reused outside selftests as well.

Keep the helpers exposed to mm selftests through vm_util.h by including
the new shared header there, and link the new helper into the selftests/mm
build.

Update the explicit x86 protection_keys 32-bit and 64-bit build rules to
preserve prerequisite paths, now that file_utils.c is built from
tools/lib/mm.

Add tools/lib/mm/ to the MEMORY MANAGEMENT - MISC entry in MAINTAINERS.

Link: https://lore.kernel.org/20260904123631.198697-3-sarthak.sharma@arm.com
Signed-off-by: Sarthak Sharma <sarthak.sharma@arm.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 MAINTAINERS                          |    1 
 tools/lib/mm/file_utils.c            |  106 +++++++++++++++++++++++++
 tools/lib/mm/file_utils.h            |   13 +++
 tools/testing/selftests/mm/Makefile  |   11 +-
 tools/testing/selftests/mm/vm_util.c |   97 ----------------------
 tools/testing/selftests/mm/vm_util.h |    7 -
 6 files changed, 127 insertions(+), 108 deletions(-)

--- a/MAINTAINERS~tools-lib-mm-add-shared-file-helpers
+++ a/MAINTAINERS
@@ -17292,6 +17292,7 @@ F:	mm/memory-tiers.c
 F:	mm/page_idle.c
 F:	mm/pgalloc-track.h
 F:	mm/process_vm_access.c
+F:	tools/lib/mm/
 F:	tools/testing/selftests/mm/
 
 MEMORY MANAGEMENT - NUMA MEMBLOCKS AND NUMA EMULATION
diff --git a/tools/lib/mm/file_utils.c a/tools/lib/mm/file_utils.c
new file mode 100644
--- /dev/null
+++ a/tools/lib/mm/file_utils.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "file_utils.h"
+
+int read_file(const char *path, char *buf, size_t buflen)
+{
+	int fd, err;
+	ssize_t numread;
+
+	fd = open(path, O_RDONLY);
+	if (fd == -1)
+		return -errno;
+
+	numread = read(fd, buf, buflen - 1);
+	if (numread < 1) {
+		err = numread ? errno : ENODATA;
+		close(fd);
+		return -err;
+	}
+
+	buf[numread] = '\0';
+	close(fd);
+
+	return 0;
+}
+
+int write_file(const char *path, const char *buf, size_t buflen)
+{
+	int fd, saved_errno;
+	ssize_t numwritten;
+
+	if (buflen < 2)
+		return -EINVAL;
+
+	fd = open(path, O_WRONLY);
+	if (fd == -1)
+		return -errno;
+
+	numwritten = write(fd, buf, buflen - 1);
+	saved_errno = errno;
+	close(fd);
+
+	if (numwritten < 0)
+		return -saved_errno;
+
+	if (numwritten != (ssize_t)(buflen - 1))
+		return -EIO;
+
+	return 0;
+}
+
+int read_num(const char *path, unsigned long *num)
+{
+	unsigned long val;
+	int ret;
+	char buf[21];
+	char *end;
+
+	if (!num)
+		return -EINVAL;
+
+	ret = read_file(path, buf, sizeof(buf));
+	if (ret)
+		return ret;
+
+	/* Reject signs and leading whitespace that are accepted by strtoul() */
+	if (buf[0] < '0' || buf[0] > '9')
+		return -EINVAL;
+
+	errno = 0;
+	val = strtoul(buf, &end, 10);
+	if (errno)
+		return -errno;
+
+	/* Only allow a newline after the number */
+	if (*end == '\n')
+		end++;
+
+	if (*end != '\0')
+		return -EINVAL;
+
+	*num = val;
+	return 0;
+}
+
+int write_num(const char *path, unsigned long num)
+{
+	char buf[21];
+
+	sprintf(buf, "%lu", num);
+	return write_file(path, buf, strlen(buf) + 1);
+}
+
+int write_num_ignore_einval(const char *path, unsigned long num)
+{
+	int ret;
+
+	ret = write_num(path, num);
+	return ret == -EINVAL ? 0 : ret;
+}
diff --git a/tools/lib/mm/file_utils.h a/tools/lib/mm/file_utils.h
new file mode 100644
--- /dev/null
+++ a/tools/lib/mm/file_utils.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __MM_FILE_UTILS_H__
+#define __MM_FILE_UTILS_H__
+
+#include <stddef.h>
+
+int read_file(const char *path, char *buf, size_t buflen);
+int write_file(const char *path, const char *buf, size_t buflen);
+int read_num(const char *path, unsigned long *num);
+int write_num(const char *path, unsigned long num);
+int write_num_ignore_einval(const char *path, unsigned long num);
+
+#endif
--- a/tools/testing/selftests/mm/Makefile~tools-lib-mm-add-shared-file-helpers
+++ a/tools/testing/selftests/mm/Makefile
@@ -37,7 +37,8 @@ endif
 # LDLIBS.
 MAKEFLAGS += --no-builtin-rules
 
-CFLAGS = -Wall -O2 -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES) $(TOOLS_INCLUDES)
+CFLAGS = -Wall -O2 -I $(top_srcdir) -I $(top_srcdir)/tools/lib
+CFLAGS += $(EXTRA_CFLAGS) $(KHDR_INCLUDES) $(TOOLS_INCLUDES)
 CFLAGS += -Wunreachable-code
 LDLIBS = -lrt -lpthread -lm
 
@@ -187,8 +188,8 @@ TEST_FILES += write_hugetlb_memory.sh
 
 include ../lib.mk
 
-$(TEST_GEN_PROGS): vm_util.c hugepage_settings.c
-$(TEST_GEN_FILES): vm_util.c hugepage_settings.c
+$(TEST_GEN_PROGS): vm_util.c hugepage_settings.c $(top_srcdir)/tools/lib/mm/file_utils.c
+$(TEST_GEN_FILES): vm_util.c hugepage_settings.c $(top_srcdir)/tools/lib/mm/file_utils.c
 
 $(OUTPUT)/uffd-stress: uffd-common.c
 $(OUTPUT)/uffd-unit-tests: uffd-common.c
@@ -217,7 +218,7 @@ $(BINARIES_32): CFLAGS += -m32 -mxsave
 $(BINARIES_32): LDLIBS += -lrt -ldl -lm
 $(BINARIES_32): $(OUTPUT)/%_32: %.c
 	$(call msg,CC,,$@)
-	$(Q)$(CC) $(CFLAGS) $(EXTRA_CFLAGS) $(notdir $^) $(LDLIBS) -o $@
+	$(Q)$(CC) $(CFLAGS) $(EXTRA_CFLAGS) $^ $(LDLIBS) -o $@
 $(foreach t,$(VMTARGETS),$(eval $(call gen-target-rule-32,$(t))))
 endif
 
@@ -226,7 +227,7 @@ $(BINARIES_64): CFLAGS += -m64 -mxsave
 $(BINARIES_64): LDLIBS += -lrt -ldl
 $(BINARIES_64): $(OUTPUT)/%_64: %.c
 	$(call msg,CC,,$@)
-	$(Q)$(CC) $(CFLAGS) $(EXTRA_CFLAGS) $(notdir $^) $(LDLIBS) -o $@
+	$(Q)$(CC) $(CFLAGS) $(EXTRA_CFLAGS) $^ $(LDLIBS) -o $@
 $(foreach t,$(VMTARGETS),$(eval $(call gen-target-rule-64,$(t))))
 endif
 
--- a/tools/testing/selftests/mm/vm_util.c~tools-lib-mm-add-shared-file-helpers
+++ a/tools/testing/selftests/mm/vm_util.c
@@ -885,103 +885,6 @@ int unpoison_memory(unsigned long pfn)
 	return ret > 0 ? 0 : -errno;
 }
 
-int read_file(const char *path, char *buf, size_t buflen)
-{
-	int fd, err;
-	ssize_t numread;
-
-	fd = open(path, O_RDONLY);
-	if (fd == -1)
-		return -errno;
-
-	numread = read(fd, buf, buflen - 1);
-	if (numread < 1) {
-		err = numread ? errno : ENODATA;
-		close(fd);
-		return -err;
-	}
-
-	buf[numread] = '\0';
-	close(fd);
-
-	return 0;
-}
-
-int write_file(const char *path, const char *buf, size_t buflen)
-{
-	int fd, saved_errno;
-	ssize_t numwritten;
-
-	if (buflen < 2)
-		return -EINVAL;
-
-	fd = open(path, O_WRONLY);
-	if (fd == -1)
-		return -errno;
-
-	numwritten = write(fd, buf, buflen - 1);
-	saved_errno = errno;
-	close(fd);
-
-	if (numwritten < 0)
-		return -saved_errno;
-
-	if (numwritten != (ssize_t)(buflen - 1))
-		return -EIO;
-
-	return 0;
-}
-
-int read_num(const char *path, unsigned long *num)
-{
-	unsigned long val;
-	int ret;
-	char buf[21];
-	char *end;
-
-	if (!num)
-		return -EINVAL;
-
-	ret = read_file(path, buf, sizeof(buf));
-	if (ret)
-		return ret;
-
-	/* Reject signs and leading whitespace that are accepted by strtoul() */
-	if (buf[0] < '0' || buf[0] > '9')
-		return -EINVAL;
-
-	errno = 0;
-	val = strtoul(buf, &end, 10);
-	if (errno)
-		return -errno;
-
-	/* Only allow a newline after the number */
-	if (*end == '\n')
-		end++;
-
-	if (*end != '\0')
-		return -EINVAL;
-
-	*num = val;
-	return 0;
-}
-
-int write_num(const char *path, unsigned long num)
-{
-	char buf[21];
-
-	sprintf(buf, "%lu", num);
-	return write_file(path, buf, strlen(buf) + 1);
-}
-
-int write_num_ignore_einval(const char *path, unsigned long num)
-{
-	int ret;
-
-	ret = write_num(path, num);
-	return ret == -EINVAL ? 0 : ret;
-}
-
 static unsigned long shmall, shmmax;
 
 void __shm_limits_restore(void)
--- a/tools/testing/selftests/mm/vm_util.h~tools-lib-mm-add-shared-file-helpers
+++ a/tools/testing/selftests/mm/vm_util.h
@@ -8,6 +8,7 @@
 #include <unistd.h> /* _SC_PAGESIZE */
 #include "kselftest.h"
 #include <linux/fs.h>
+#include <mm/file_utils.h>
 
 #define BIT_ULL(nr)                   (1ULL << (nr))
 #define PM_SOFT_DIRTY                 BIT_ULL(55)
@@ -166,12 +167,6 @@ int unpoison_memory(unsigned long pfn);
 #define PAGEMAP_PRESENT(ent)	(((ent) & (1ull << 63)) != 0)
 #define PAGEMAP_PFN(ent)	((ent) & ((1ull << 55) - 1))
 
-int write_file(const char *path, const char *buf, size_t buflen);
-int read_file(const char *path, char *buf, size_t buflen);
-int read_num(const char *path, unsigned long *num);
-int write_num(const char *path, unsigned long num);
-int write_num_ignore_einval(const char *path, unsigned long num);
-
 void shm_limits_prepare(unsigned long length);
 void __shm_limits_restore(void);
 
_

Patches currently in -mm which might be from sarthak.sharma@arm.com are

mm-gup_test-report-actual-pinned-bytes.patch
selftests-mm-make-file-helpers-return-errors.patch
tools-lib-mm-add-shared-file-helpers.patch
tools-lib-mm-move-hugepage_settings-out-of-selftests.patch
tools-mm-move-gup_test-from-selftests-mm-to-tools-mm.patch
tools-mm-make-gup_bench-a-benchmark-only-tool.patch
selftests-mm-add-a-gup-selftest.patch