From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8E06B3DEAF9 for ; Tue, 26 May 2026 11:22:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779794558; cv=none; b=hbW1m6a+11QsjGzYoyn+mdl+J7pdmJLSbcZM3Pl3xXLqfneMzKNTMxZXfMjn10R2OSCKKUu/jjz4QZBwQaJ2S6aZRk3O59+i2jbc5+uV6ZOO2fCBfzmRrrZegRXVgw70lhFdLaGsYbmojIcHfN7hN8+bDC4tr358x2Hw1HYTgys= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779794558; c=relaxed/simple; bh=4SThAaLN45W0VRfW7eUFmUMdPxh9aMgDxZE2EX6AeBc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=T2AwS5QeGpxPTZfRkjxTAj0/4hI+vpG4unK9QPgbyhlZiz5yCF7RBOPxbCOPclqW+CAKKKYDTvD8LZRKtvamHJm67yRAswLRdOUUptN9LkN4nM6nB/rsIyvK9iuVe07uyehNmzKCwLDpHLL+bOVJ9+bVOuZMbJAI0xSachDqzac= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AINgodxR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AINgodxR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75D231F000E9; Tue, 26 May 2026 11:22:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779794557; bh=edtMl0k6/AxJMdXk+W1fbU3ZPltq/7vhq9xYg9auTlw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260525102700.68707-2-ranxiaokai627@163.com> 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 > >