mm: huge_memory: refactor enabled_store() with set_global_enabled_mode()

Refactor enabled_store() to use a new set_global_enabled_mode() helper.
Introduce a separate enum global_enabled_mode and
global_enabled_mode_strings[], mirroring the anon_enabled_mode pattern
from the previous commit.

A separate enum is necessary because the global THP setting does not
support "inherit", only "always", "madvise", and "never".  Reusing
anon_enabled_mode would leave a NULL gap in the string array, causing
sysfs_match_string() to stop early and fail to match entries after the
gap.

The helper uses the same loop pattern as set_anon_enabled_mode(),
iterating over an array of flag bit positions and using
test_and_set_bit()/test_and_clear_bit() to track whether the state
actually changed.

Link: https://lkml.kernel.org/r/20260317-thp_logs-v7-3-31eb98fa5a8b@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 211d8c8923188344103d4c93da8025558f6a8209..9fea52ccad56165dc3e41ee6f4da6e4d2a115f88 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -330,30 +330,63 @@ static const char * const anon_enabled_mode_strings[] = {
        [ANON_ENABLED_NEVER]    = "never",
 };
 
+enum global_enabled_mode {
+       GLOBAL_ENABLED_ALWAYS   = 0,
+       GLOBAL_ENABLED_MADVISE  = 1,
+       GLOBAL_ENABLED_NEVER    = 2,
+};
+
+static const char * const global_enabled_mode_strings[] = {
+       [GLOBAL_ENABLED_ALWAYS]         = "always",
+       [GLOBAL_ENABLED_MADVISE]        = "madvise",
+       [GLOBAL_ENABLED_NEVER]          = "never",
+};
+
+static bool set_global_enabled_mode(enum global_enabled_mode mode)
+{
+       static const unsigned long thp_flags[] = {
+               TRANSPARENT_HUGEPAGE_FLAG,
+               TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
+       };
+       enum global_enabled_mode m;
+       bool changed = false;
+
+       for (m = 0; m < ARRAY_SIZE(thp_flags); m++) {
+               if (m == mode)
+                       changed |= !test_and_set_bit(thp_flags[m],
+                                                    &transparent_hugepage_flags);
+               else
+                       changed |= test_and_clear_bit(thp_flags[m],
+                                                     &transparent_hugepage_flags);
+       }
+
+       return changed;
+}
+
 static ssize_t enabled_store(struct kobject *kobj,
                             struct kobj_attribute *attr,
                             const char *buf, size_t count)
 {
-       ssize_t ret = count;
+       int mode;
 
-       if (sysfs_streq(buf, "always")) {
-               clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
-               set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
-       } else if (sysfs_streq(buf, "madvise")) {
-               clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
-               set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
-       } else if (sysfs_streq(buf, "never")) {
-               clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
-               clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
-       } else
-               ret = -EINVAL;
+       mode = sysfs_match_string(global_enabled_mode_strings, buf);
+       if (mode < 0)
+               return -EINVAL;
 
-       if (ret > 0) {
+       if (set_global_enabled_mode(mode)) {
                int err = start_stop_khugepaged();
+
                if (err)
-                       ret = err;
+                       return err;
+       } else {
+               /*
+                * Recalculate watermarks even when the mode didn't
+                * change, as the previous code always called
+                * start_stop_khugepaged() which does this internally.
+                */
+               set_recommended_min_free_kbytes();
        }
-       return ret;
+       return count;
 }
 
 static struct kobj_attribute enabled_attr = __ATTR_RW(enabled);