mm: huge_memory: refactor defrag_show() to use defrag_flags[]

Replace the hardcoded if/else chain of test_bit() calls and string
literals in defrag_show() with a loop over defrag_flags[] and
defrag_mode_strings[] arrays introduced in the previous commit.

This makes defrag_show() consistent with defrag_store() and eliminates the
duplicated mode name strings.

Link: https://lore.kernel.org/20260408-thp_defrag-v2-2-bc544c1bde4e@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Tested-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Tested-by: Zi Yan <ziy@nvidia.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam@infradead.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 62e00b21fdf42d85f2d6ab89c5f638e18abfcf06..e9d499da0ac739ef254b1cb6673228e0e7543f71 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -455,24 +455,30 @@ static const enum transparent_hugepage_flag defrag_flags[] = {
 static ssize_t defrag_show(struct kobject *kobj,
                           struct kobj_attribute *attr, char *buf)
 {
-       const char *output;
+       int active = DEFRAG_NEVER;
+       int len = 0;
+       int i;
 
-       if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
-                    &transparent_hugepage_flags))
-               output = "[always] defer defer+madvise madvise never";
-       else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
-                         &transparent_hugepage_flags))
-               output = "always [defer] defer+madvise madvise never";
-       else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
-                         &transparent_hugepage_flags))
-               output = "always defer [defer+madvise] madvise never";
-       else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
-                         &transparent_hugepage_flags))
-               output = "always defer defer+madvise [madvise] never";
-       else
-               output = "always defer defer+madvise madvise [never]";
+       for (i = 0; i < ARRAY_SIZE(defrag_flags); i++) {
+               if (test_bit(defrag_flags[i], &transparent_hugepage_flags)) {
+                       active = i;
+                       break;
+               }
+       }
 
-       return sysfs_emit(buf, "%s\n", output);
+       for (i = 0; i < ARRAY_SIZE(defrag_mode_strings); i++) {
+               if (i == active)
+                       len += sysfs_emit_at(buf, len, "[%s] ",
+                                            defrag_mode_strings[i]);
+               else
+                       len += sysfs_emit_at(buf, len, "%s ",
+                                            defrag_mode_strings[i]);
+       }
+
+       /* Replace trailing space with newline */
+       buf[len - 1] = '\n';
+
+       return len;
 }
 
 static ssize_t defrag_store(struct kobject *kobj,