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b=KUoZFdLUDU9dQJPqSCO9C6gQSCR0wmQOHEkAhk6GV7lACRVbL8jphh1UpZBGmK7ek x8+5sfXZat9PV90ys5OITbORfkRnxIapxJ3lUl0oiswBsZ048Cc7D3lHrworRgt01j xoqdHBFCL17jXe/hrJczO2D4BZQOFhVBoNVLxtZS09ragaEeTvA7eMycy6vhck17RY 92BrXnNumkyhr8iHgiuwuNjtzVBjr79+NfmrtZJ1+MWfF5DDO9mRMngQio2UHQDfFZ c5Kh7adfGIhL+2cykEmCtqhOLCn1hLDPKntm6a6dVbOGMIRN1+xCah9HoAgS8boRtS 3jEbf4Rke2fTA== Date: Fri, 22 May 2026 11:55:20 +0100 From: Lorenzo Stoakes To: ranxiaokai627@163.com Cc: hughd@google.com, baolin.wang@linux.alibaba.com, akpm@linux-foundation.org, 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 Subject: Re: [PATCH v3 1/2] mm: shmem: refactor thpsize_shmem_enabled_store() with sysfs_match_string() Message-ID: References: <20260518123238.56344-1-ranxiaokai627@163.com> <20260518123238.56344-2-ranxiaokai627@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 5r71hzfjauqir5g3fjsojkiowzdai9ze X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C5B2F180002 X-Rspam-User: X-HE-Tag: 1779447328-321347 X-HE-Meta: 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 KxQHFKvz FbuQkpvJ2h1MiKjQoj5KFUbfoMsLxxhLCV/m9xsFxMWRpnFhQf8DGJQOA7heJzPeHJ/tySVA9UrxXqQCj48Px/vSLKsy4cAlmPi8bJD7rWHZm364oU7lBIUUAjphgEpdclpxA8OfO1/Scw1m3cHVh9ELu8hq408P7OQXfO0PzyiBSrRZEk6SjbcQ10Q4ddyoSG3uyItHYusRWKrwuq7olD3VKv8rSsBHq2a1xv3OsdlynpyEoNST91fXoWGltNI1E5lmtp8zExWzyufIb2GPns1N46qppJGqwheV0iYiQ4EX7ty6VOXYB9UpcYGgyNT47rkJJIPj9uJ5nOf5W7kllT7yChR04c4PULW4N95aQqqxwfveLrQapjPnip8+0sjMphrkx Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, May 22, 2026 at 11:39:45AM +0100, Lorenzo Stoakes wrote: > On Mon, May 18, 2026 at 12:32:37PM +0000, 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. > > > > 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 > > Your From: and Signed-off-by: differs. As per my mail to the 2/2 this violates > kernel process rules. Please either update the signed-off-by to your @163.com > address or resend from your zte.com.cn address. Apologies, again I (somehow) missed the in-body From: :P You're good, ignore this. But do please look at the suggest below re: naming! Thanks :) > > Logic generally looks good, but you need to fix your From/Signed-off-by and the > rename suggested below would be good. > > Thanks, Lorenzo > > > --- > > mm/shmem.c | 107 ++++++++++++++++++++++++++++++----------------------- > > 1 file changed, 60 insertions(+), 47 deletions(-) > > > > diff --git a/mm/shmem.c b/mm/shmem.c > > index 3b5dc21b323c..46d2cfc30823 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, > > +}; > > As Baolin suggested, we can probably rename these for bervity. > > We know it's shmem, as it's in shmem.c :) so drop that. > > huge_mode, huge_mode_strings, huge_mode_orders seems good to me? > > > + > > 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_shmem_enabled_mode mode) > > +{ > > + bool changed = false; > > + enum huge_shmem_enabled_mode idx; > > + > > + spin_lock(&huge_shmem_orders_lock); > > + for (idx = 0; idx < ARRAY_SIZE(huge_shmem_orders_by_mode); idx++) { > > + if (idx == mode) > > + changed |= !__test_and_set_bit(order, huge_shmem_orders_by_mode[idx]); > > + else > > + changed |= __test_and_clear_bit(order, huge_shmem_orders_by_mode[idx]); > > + } > > + spin_unlock(&huge_shmem_orders_lock); > > + > > + return changed; > > +} > > + > > Thanks for separating this out! :) > > > 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_shmem_enabled_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 > > > >