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b=AINgodxRC2K92xgnNlj3DqwmDj736yWVpDLEcWDXIopQTHVb7fGM/1IwAMr625HkB SquHMFJZmioC8PJUydGZ0zYNvfDv1Z1upjkkEyEH0YkRJSnkLmt4UJ0qLUSgJx5Li0 ispi1RDBPz0N0thtEb6qawMp4JdUthyhV7hDVMhgaB/4T4ltmSpKPfJ6Z8z6nR8jRO vbXGqBU2TB373rbZEJizjPq99aQ0d1sThoBepA3kjgibEjquCLuGcAUx07dxcJaWKB 9Vg8XhdFTov+UrfhHWdYZr1ok2qEJ7HoRn8nnU1j0Po7tQBKFiPWEmzXCslQJouTHc LrOK20+kwoRVA== Date: Tue, 26 May 2026 12:22:30 +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 v4 1/2] mm: shmem: refactor thpsize_shmem_enabled_store() with sysfs_match_string() Message-ID: References: <20260525102700.68707-1-ranxiaokai627@163.com> <20260525102700.68707-2-ranxiaokai627@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260525102700.68707-2-ranxiaokai627@163.com> X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2932C4000D X-Stat-Signature: x5jbe1jiuh9au5du54cer5qkh8pg44fp X-HE-Tag: 1779794558-896536 X-HE-Meta: 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 qoehnKZl gRBQjyaQo+OB3uEzIHt9syu9hluaTD6MHlHFxwplgINm98zGbY99571NBIYLgknQSI9ZDCYCxK4Z5JGE/Scy/DhZCQUXsPdT2CxseS6xekCdT90bphVHhznHQIZqQqk8EPibWqq9RWPPJXplMPSykEGnbbs15EukN3gFRB1MzOxoz/OeUmn2KiX0Hmlp5d9Mi8g9nubXi/byHX6PHIKCvfbfeNy9C1H4fFnaoqde+gJawoHWsH6NXOOdiyVWgR01byVBnG7KFdv7ipaFzM2KhJSMJIOgYMApjbTMIu1XnAH4/ITZZK679PRiEziudi4usSJgPhBFq8QB5fzLW45Ag/9+aWLeFCq9BxBan630rkb7zovtBdT/hp0/6By6OvSBr+yUOWZm1cPxV9uyW+24rNeXMH23bfvJ5wsfNBW3D6J4wThY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, May 25, 2026 at 10:26:59AM +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 LGTM, so: Reviewed-by: Lorenzo Stoakes > 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 > >