selftests/mm: vm_util: add helpers to set and restore shm limits

hugetlb-shm and thuge-gen tests require that limits defined by
/proc/sys/kernel/{shmmax,shmall} should be higher than certain values.

Add helpers that allow setting these limits and restoring their settings
on a test exit.

They will be used later in hugetlb-shm and thuge-gen.

Link: https://lore.kernel.org/20260511162840.375890-31-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Tested-by: Luiz Capitulino <luizcap@redhat.com>
Tested-by: Sarthak Sharma <sarthak.sharma@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Donet Tom <donettom@linux.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam@infradead.org>
Cc: Li Wang <li.wang@linux.dev>
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>

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 9256bbbe38ead834cf8d0eac085c73825da0ec69..336a26751d3faec7a586021e15b48bcd5b62805b 100644 (file)
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -760,3 +760,31 @@ void write_num(const char *path, unsigned long num)
        sprintf(buf, "%lu", num);
        write_file(path, buf, strlen(buf) + 1);
 }
+
+static unsigned long shmall, shmmax;
+
+void __shm_limits_restore(void)
+{
+       if (shmmax)
+               write_num("/proc/sys/kernel/shmmax", shmmax);
+       if (shmall)
+               write_num("/proc/sys/kernel/shmall", shmall);
+}
+
+void shm_limits_prepare(unsigned long length)
+{
+       unsigned long nr = length / psize();
+       unsigned long val;
+
+       val = read_num("/proc/sys/kernel/shmmax");
+       if (val < length) {
+               write_num("/proc/sys/kernel/shmmax", length);
+               shmmax = val;
+       }
+
+       val = read_num("/proc/sys/kernel/shmall");
+       if (val < nr) {
+               write_num("/proc/sys/kernel/shmall", nr);
+               shmall = val;
+       }
+}

diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index 5fc9707f6b9a1c9561dc1979606aa8996ca625ef..ea8fc8fdf0eb0b1d22257a8e5c5ba357c606fb34 100644 (file)
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -168,3 +168,12 @@ void write_file(const char *path, const char *buf, size_t buflen);
 int read_file(const char *path, char *buf, size_t buflen);
 unsigned long read_num(const char *path);
 void write_num(const char *path, unsigned long num);
+
+void shm_limits_prepare(unsigned long length);
+void __shm_limits_restore(void);
+
+#define SHM_LIMITS_RESTORE()                                           \
+static void __attribute__((destructor)) shm_limits_restore(void)       \
+{                                                                      \
+       __shm_limits_restore();                                         \
+}