[PATCH 1/2] mm: huge_memory: use sysfs_match_string() in defrag_store()

[Breno Leitao]

Replace the if/else chain of sysfs_streq() calls in defrag_store()
with sysfs_match_string() and a defrag_mode_strings[] table.

Introduce enum defrag_mode and defrag_flags[] array mapping each mode
to its corresponding transparent_hugepage_flag. The store function now
loops over defrag_flags[], setting the bit for the selected mode and
clearing the others. When mode is DEFRAG_NEVER (index 4), no index
in the 4-element defrag_flags[] matches, so all flags are cleared.

Note that the enum ordering (always, defer, defer+madvise, madvise,
never) differs from the original if/else chain order in defrag_store()
(always, defer+madvise, defer, madvise, never). This is intentional to
match the display order used by defrag_show().

This is a follow-up cleanup to commit 522dfb4ba71f ("mm: huge_memory:
refactor anon_enabled_store() with change_anon_orders()") which applied
the same sysfs_match_string() pattern to anon_enabled_store().

Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
 mm/huge_memory.c | 60 ++++++++++++++++++++++++++++++++------------------------
 1 file changed, 34 insertions(+), 26 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3fc02913b63e3..4843e2154038f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -421,6 +421,29 @@ ssize_t single_hugepage_flag_store(struct kobject *kobj,
 	return count;
 }
 
+enum defrag_mode {
+	DEFRAG_ALWAYS		= 0,
+	DEFRAG_DEFER		= 1,
+	DEFRAG_DEFER_MADVISE	= 2,
+	DEFRAG_MADVISE		= 3,
+	DEFRAG_NEVER		= 4,
+};
+
+static const char * const defrag_mode_strings[] = {
+	[DEFRAG_ALWAYS]		= "always",
+	[DEFRAG_DEFER]		= "defer",
+	[DEFRAG_DEFER_MADVISE]	= "defer+madvise",
+	[DEFRAG_MADVISE]	= "madvise",
+	[DEFRAG_NEVER]		= "never",
+};
+
+static const enum transparent_hugepage_flag defrag_flags[] = {
+	[DEFRAG_ALWAYS]		= TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
+	[DEFRAG_DEFER]		= TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
+	[DEFRAG_DEFER_MADVISE]	= TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
+	[DEFRAG_MADVISE]	= TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
+};
+
 static ssize_t defrag_show(struct kobject *kobj,
 			   struct kobj_attribute *attr, char *buf)
 {
@@ -448,34 +471,19 @@ static ssize_t defrag_store(struct kobject *kobj,
 			    struct kobj_attribute *attr,
 			    const char *buf, size_t count)
 {
-	if (sysfs_streq(buf, "always")) {
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
-		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
-	} else if (sysfs_streq(buf, "defer+madvise")) {
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
-		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
-	} else if (sysfs_streq(buf, "defer")) {
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
-		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
-	} else if (sysfs_streq(buf, "madvise")) {
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
-		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
-	} else if (sysfs_streq(buf, "never")) {
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
-		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
-	} else
+	int mode, m;
+
+	mode = sysfs_match_string(defrag_mode_strings, buf);
+	if (mode < 0)
 		return -EINVAL;
 
+	for (m = 0; m < ARRAY_SIZE(defrag_flags); m++) {
+		if (m == mode)
+			set_bit(defrag_flags[m], &transparent_hugepage_flags);
+		else
+			clear_bit(defrag_flags[m], &transparent_hugepage_flags);
+	}
+
 	return count;
 }
 static struct kobj_attribute defrag_attr = __ATTR_RW(defrag);

-- 
2.52.0