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mm: shmem: refactor thpsize_shmem_enabled_store() with sysfs_match_string()

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Patch series "refactors thpsize_shmem_enabled_store() and
thpsize_shmem_enabled_show()", v4.


This patch (of 2):

Inspired by commit 82d9ff648c ("mm: huge_memory: refactor
anon_enabled_store() with set_anon_enabled_mode()"), refactor
thpsize_shmem_enabled_store() using sysfs_match_string().  This eliminates
the duplicated spin_lock/unlock(), set/clear_bit(), calls across all
branches, reducing code duplication.

Behavioral change:
Call start_stop_khugepaged() only when the mode actually changes.
If unchanged, call set_recommended_min_free_kbytes() to preserve
legacy watermark behavior. This avoids unnecessary khugepaged restarts.

Tested with selftests ./run_kselftest.sh -t mm:ksft_thp.sh,
all test cases passed.

Link: https://lore.kernel.org/20260525102700.68707-1-ranxiaokai627@163.com
Link: https://lore.kernel.org/20260525102700.68707-2-ranxiaokai627@163.com
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Lance Yang <lance.yang@linux.dev>
Acked-by: David Hildenbrand (arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Cc: Breno Leitao <leitao@debian.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ran Xiaokai 2026-05-25 10:26:59 +00:00 committed by Andrew Morton
parent eb4c458a98
commit ad1cee3940
1 changed files with 59 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

105
mm/shmem.c
View File

@ -5463,6 +5463,29 @@ static ssize_t shmem_enabled_store(struct kobject *kobj,
struct kobj_attribute shmem_enabled_attr = __ATTR_RW(shmem_enabled);
static DEFINE_SPINLOCK(huge_shmem_orders_lock);
enum huge_mode {
HUGE_SHMEM_ENABLED_ALWAYS = 0,
HUGE_SHMEM_ENABLED_INHERIT,
HUGE_SHMEM_ENABLED_WITHIN_SIZE,
HUGE_SHMEM_ENABLED_ADVISE,
HUGE_SHMEM_ENABLED_NEVER,
};
static const char * const huge_mode_strings[] = {
[HUGE_SHMEM_ENABLED_ALWAYS] = "always",
[HUGE_SHMEM_ENABLED_INHERIT] = "inherit",
[HUGE_SHMEM_ENABLED_WITHIN_SIZE] = "within_size",
[HUGE_SHMEM_ENABLED_ADVISE] = "advise",
[HUGE_SHMEM_ENABLED_NEVER] = "never",
};
static unsigned long * const huge_mode_orders[] = {
[HUGE_SHMEM_ENABLED_ALWAYS] = &huge_shmem_orders_always,
[HUGE_SHMEM_ENABLED_INHERIT] = &huge_shmem_orders_inherit,
[HUGE_SHMEM_ENABLED_WITHIN_SIZE] = &huge_shmem_orders_within_size,
[HUGE_SHMEM_ENABLED_ADVISE] = &huge_shmem_orders_madvise,
};
static ssize_t thpsize_shmem_enabled_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
@ -5483,63 +5506,53 @@ static ssize_t thpsize_shmem_enabled_show(struct kobject *kobj,
return sysfs_emit(buf, "%s\n", output);
}
static bool set_shmem_enabled_mode(int order, enum huge_mode mode)
{
bool changed = false;
enum huge_mode idx;
spin_lock(&huge_shmem_orders_lock);
for (idx = 0; idx < ARRAY_SIZE(huge_mode_orders); idx++) {
if (idx == mode)
changed |= !__test_and_set_bit(order, huge_mode_orders[idx]);
else
changed |= __test_and_clear_bit(order, huge_mode_orders[idx]);
}
spin_unlock(&huge_shmem_orders_lock);
return changed;
}
static ssize_t thpsize_shmem_enabled_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int order = to_thpsize(kobj)->order;
ssize_t ret = count;
int mode;
if (sysfs_streq(buf, "always")) {
spin_lock(&huge_shmem_orders_lock);
clear_bit(order, &huge_shmem_orders_inherit);
clear_bit(order, &huge_shmem_orders_madvise);
clear_bit(order, &huge_shmem_orders_within_size);
set_bit(order, &huge_shmem_orders_always);
spin_unlock(&huge_shmem_orders_lock);
} else if (sysfs_streq(buf, "inherit")) {
/* Do not override huge allocation policy with non-PMD sized mTHP */
if (shmem_huge == SHMEM_HUGE_FORCE && !is_pmd_order(order))
return -EINVAL;
mode = sysfs_match_string(huge_mode_strings, buf);
if (mode < 0)
return mode;
spin_lock(&huge_shmem_orders_lock);
clear_bit(order, &huge_shmem_orders_always);
clear_bit(order, &huge_shmem_orders_madvise);
clear_bit(order, &huge_shmem_orders_within_size);
set_bit(order, &huge_shmem_orders_inherit);
spin_unlock(&huge_shmem_orders_lock);
} else if (sysfs_streq(buf, "within_size")) {
spin_lock(&huge_shmem_orders_lock);
clear_bit(order, &huge_shmem_orders_always);
clear_bit(order, &huge_shmem_orders_inherit);
clear_bit(order, &huge_shmem_orders_madvise);
set_bit(order, &huge_shmem_orders_within_size);
spin_unlock(&huge_shmem_orders_lock);
} else if (sysfs_streq(buf, "advise")) {
spin_lock(&huge_shmem_orders_lock);
clear_bit(order, &huge_shmem_orders_always);
clear_bit(order, &huge_shmem_orders_inherit);
clear_bit(order, &huge_shmem_orders_within_size);
set_bit(order, &huge_shmem_orders_madvise);
spin_unlock(&huge_shmem_orders_lock);
} else if (sysfs_streq(buf, "never")) {
spin_lock(&huge_shmem_orders_lock);
clear_bit(order, &huge_shmem_orders_always);
clear_bit(order, &huge_shmem_orders_inherit);
clear_bit(order, &huge_shmem_orders_within_size);
clear_bit(order, &huge_shmem_orders_madvise);
spin_unlock(&huge_shmem_orders_lock);
} else {
ret = -EINVAL;
}
/* Do not override huge allocation policy with non-PMD sized mTHP */
if (mode == HUGE_SHMEM_ENABLED_INHERIT &&
shmem_huge == SHMEM_HUGE_FORCE && !is_pmd_order(order))
return -EINVAL;
if (ret > 0) {
if (set_shmem_enabled_mode(order, mode)) {
int err = start_stop_khugepaged();
if (err)
ret = err;
return err;
} else {
/*
* Recalculate watermarks even when the mode hasn't changed
* to preserve the legacy behavior, as this is always called
* inside start_stop_khugepaged().
*/
set_recommended_min_free_kbytes();
}
return ret;
return count;
}
struct kobj_attribute thpsize_shmem_enabled_attr =