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(unknown []) by gzga-smtp-mtada-g1-4 (Coremail) with SMTP id _____wD3V9L2IxRqXqahDg--.22926S3; Mon, 25 May 2026 18:27:04 +0800 (CST) From: ranxiaokai627@163.com To: ljs@kernel.org, hughd@google.com, baolin.wang@linux.alibaba.com, akpm@linux-foundation.org Cc: leitao@debian.org, ziy@nvidia.com, liam@infradead.org, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, david@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ran.xiaokai@zte.com.cn, ranxiaokai627@163.com Subject: [PATCH v4 1/2] mm: shmem: refactor thpsize_shmem_enabled_store() with sysfs_match_string() Date: Mon, 25 May 2026 10:26:59 +0000 Message-ID: <20260525102700.68707-2-ranxiaokai627@163.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260525102700.68707-1-ranxiaokai627@163.com> References: <20260525102700.68707-1-ranxiaokai627@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wD3V9L2IxRqXqahDg--.22926S3 X-Coremail-Antispam: 1Uf129KBjvJXoW3WrW8WFWUAry3Jw48Ar45Awb_yoW7Kr4DpF 4fC34fAry8Jr9rK3yxJF48tryrtrs3Ja1DtrWkJas3Aan8JryYyF1vy348Z34DJryfXr47 KF18WasFgrWDtw7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0ziqXdrUUUUU= X-CM-SenderInfo: xudq5x5drntxqwsxqiywtou0bp/xtbC7Rmm8moUI-mPVQAA3e From: Ran Xiaokai Inspired by commit 82d9ff648c6c ("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. Signed-off-by: Ran Xiaokai Reviewed-by: Baolin Wang Reviewed-by: Barry Song Tested-by: Baolin Wang Tested-by: Lance Yang --- mm/shmem.c | 107 ++++++++++++++++++++++++++++++----------------------- 1 file changed, 60 insertions(+), 47 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 3b5dc21b323c..288942b44db6 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -5526,6 +5526,29 @@ 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) { @@ -5546,63 +5569,53 @@ 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; - - 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; + int 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; - } + mode = sysfs_match_string(huge_mode_strings, buf); + if (mode < 0) + return mode; - if (ret > 0) { - int err = start_stop_khugepaged(); + /* 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 (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 = -- 2.25.1