[PATCH v2 2/2] mm: huge_memory: refactor defrag_show() to use defrag_flags[]

Breno Leitao
2026-04-08T15:47:47Z

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.

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>
Signed-off-by: Breno Leitao <leitao@debian.org>
---
mm/huge_memory.c | 38 ++++++++++++++++++++++----------------
1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 76f2d32428c7f..6993c6d8709dc 100644
--- 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,

--
2.52.0