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Received: from 30.74.144.119(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X2sFRik_1778641452 cluster:ay36) by smtp.aliyun-inc.com; Wed, 13 May 2026 11:04:13 +0800 Message-ID: <7b8cb44c-a098-4430-a8ef-142fa7a19087@linux.alibaba.com> Date: Wed, 13 May 2026 11:04:12 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm: huge_memory: refactor thpsize_shmem_enabled_store() with sysfs_match_string() To: ranxiaokai627@163.com, hughd@google.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, ran.xiaokai@zte.com.cn, "leitao@debian.org >> Breno Leitao" , "Lorenzo Stoakes (Oracle)" References: <20260512120557.49995-1-ranxiaokai627@163.com> From: Baolin Wang In-Reply-To: <20260512120557.49995-1-ranxiaokai627@163.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit CC Breno and Lorenzo On 5/12/26 8:05 PM, ranxiaokai627@163.com wrote: > 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. > > Tested with selftests ./run_kselftest.sh -t mm:ksft_thp.sh, > all test cases passed. > > Signed-off-by: Ran Xiaokai > --- Thanks for doing this. > mm/shmem.c | 88 ++++++++++++++++++++++++++---------------------------- > 1 file changed, 43 insertions(+), 45 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 3b5dc21b323c..0cc7872cc576 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_shmem_enabled_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_shmem_enabled_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_shmem_orders_by_mode[] = { > + [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) > { > @@ -5551,57 +5574,32 @@ static ssize_t thpsize_shmem_enabled_store(struct kobject *kobj, > const char *buf, size_t count) > { > int order = to_thpsize(kobj)->order; > + int mode, m; > ssize_t ret = count; > + int err; > > - 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_shmem_enabled_mode_strings, buf); > + if (mode < 0) > + return -EINVAL; > > - 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; > + > + spin_lock(&huge_shmem_orders_lock); > + for (m = 0; m < ARRAY_SIZE(huge_shmem_orders_by_mode); m++) { > + if (m == mode) > + set_bit(order, huge_shmem_orders_by_mode[m]); > + else > + clear_bit(order, huge_shmem_orders_by_mode[m]); > } We are already under the lock, so you can use non-atomic functions like commit 82d9ff648c6c does: __test_and_set_bit/__test_and_clear_bit. > + spin_unlock(&huge_shmem_orders_lock); > > - if (ret > 0) { > - int err = start_stop_khugepaged(); > + err = start_stop_khugepaged(); > + if (err) Moreover, I think we can follow commit 82d9ff648c6c's approach: if nothing changed, we don't need to call start_stop_khugepaged().