Add a new kernel command line to control the hugepage allocation policy
for the internal shmem mount, ``transparent_hugepage_shmem``. The
parameter is similar to ``transparent_hugepage`` and has the following
format:

transparent_hugepage_shmem=<policy>

where ``<policy>`` is one of the seven valid policies available for
shmem.

By configuring the default hugepage allocation policy for the internal
shmem mount, applications that use shmem, such as the DRM GEM objects,
can take advantage of mTHP before it's been configured through sysfs.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
---
 .../admin-guide/kernel-parameters.txt         |  7 ++
 Documentation/admin-guide/mm/transhuge.rst    |  6 ++
 mm/shmem.c                                    | 72 +++++++++++++------
 3 files changed, 62 insertions(+), 23 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1666576acc0e..acabb04d0dd4 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6926,6 +6926,13 @@
 			See Documentation/admin-guide/mm/transhuge.rst
 			for more details.
 
+	transparent_hugepage_shmem= [KNL]
+			Format: [always|within_size|advise|never|deny|force]
+			Can be used to control the hugepage allocation policy for
+			the internal shmem mount.
+			See Documentation/admin-guide/mm/transhuge.rst
+			for more details.
+
 	trusted.source=	[KEYS]
 			Format: <string>
 			This parameter identifies the trust source as a backend
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index 745055c3dc09..9b5b02c4d1ab 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -326,6 +326,12 @@ PMD_ORDER THP policy will be overridden. If the policy for PMD_ORDER
 is not defined within a valid ``thp_anon``, its policy will default to
 ``never``.
 
+Similarly to ``transparent_hugepage``, you can control the hugepage
+allocation policy for the internal shmem mount by using the kernel parameter
+``transparent_hugepage_shmem=<policy>``, where ``<policy>`` is one of the
+seven valid policies for shmem (``always``, ``within_size``, ``advise``,
+``never``, ``deny``, and ``force``).
+
 Hugepages in tmpfs/shmem
 ========================
 
diff --git a/mm/shmem.c b/mm/shmem.c
index 275251abd596..dfcc88ec6e34 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -582,24 +582,39 @@ static bool shmem_huge_global_enabled(struct inode *inode, pgoff_t index,
 	}
 }
 
-#if defined(CONFIG_SYSFS)
 static int shmem_parse_huge(const char *str)
 {
+	int huge;
+
+	if (!str)
+		return -EINVAL;
+
 	if (!strcmp(str, "never"))
-		return SHMEM_HUGE_NEVER;
-	if (!strcmp(str, "always"))
-		return SHMEM_HUGE_ALWAYS;
-	if (!strcmp(str, "within_size"))
-		return SHMEM_HUGE_WITHIN_SIZE;
-	if (!strcmp(str, "advise"))
-		return SHMEM_HUGE_ADVISE;
-	if (!strcmp(str, "deny"))
-		return SHMEM_HUGE_DENY;
-	if (!strcmp(str, "force"))
-		return SHMEM_HUGE_FORCE;
-	return -EINVAL;
+		huge = SHMEM_HUGE_NEVER;
+	else if (!strcmp(str, "always"))
+		huge = SHMEM_HUGE_ALWAYS;
+	else if (!strcmp(str, "within_size"))
+		huge = SHMEM_HUGE_WITHIN_SIZE;
+	else if (!strcmp(str, "advise"))
+		huge = SHMEM_HUGE_ADVISE;
+	else if (!strcmp(str, "deny"))
+		huge = SHMEM_HUGE_DENY;
+	else if (!strcmp(str, "force"))
+		huge = SHMEM_HUGE_FORCE;
+	else
+		return -EINVAL;
+
+	if (!has_transparent_hugepage() &&
+	    huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
+		return -EINVAL;
+
+	/* Do not override huge allocation policy with non-PMD sized mTHP */
+	if (huge == SHMEM_HUGE_FORCE &&
+	    huge_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
+		return -EINVAL;
+
+	return huge;
 }
-#endif
 
 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
 static const char *shmem_format_huge(int huge)
@@ -5066,15 +5081,7 @@ static ssize_t shmem_enabled_store(struct kobject *kobj,
 
 	huge = shmem_parse_huge(tmp);
 	if (huge == -EINVAL)
-		return -EINVAL;
-	if (!has_transparent_hugepage() &&
-			huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
-		return -EINVAL;
-
-	/* Do not override huge allocation policy with non-PMD sized mTHP */
-	if (huge == SHMEM_HUGE_FORCE &&
-	    huge_shmem_orders_inherit != BIT(HPAGE_PMD_ORDER))
-		return -EINVAL;
+		return huge;
 
 	shmem_huge = huge;
 	if (shmem_huge > SHMEM_HUGE_DENY)
@@ -5171,6 +5178,25 @@ struct kobj_attribute thpsize_shmem_enabled_attr =
 	__ATTR(shmem_enabled, 0644, thpsize_shmem_enabled_show, thpsize_shmem_enabled_store);
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
 
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
+
+static int __init setup_transparent_hugepage_shmem(char *str)
+{
+	int huge;
+
+	huge = shmem_parse_huge(str);
+	if (huge == -EINVAL) {
+		pr_warn("transparent_hugepage_shmem= cannot parse, ignored\n");
+		return huge;
+	}
+
+	shmem_huge = huge;
+	return 1;
+}
+__setup("transparent_hugepage_shmem=", setup_transparent_hugepage_shmem);
+
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
 #else /* !CONFIG_SHMEM */
 
 /*
-- 
2.46.2

On 30.10.24 13:58, Maíra Canal wrote:
> Add a new kernel command line to control the hugepage allocation policy
> for the internal shmem mount, ``transparent_hugepage_shmem``. The
> parameter is similar to ``transparent_hugepage`` and has the following
> format:
> 
> transparent_hugepage_shmem=<policy>
> 
> where ``<policy>`` is one of the seven valid policies available for
> shmem.
> 
> By configuring the default hugepage allocation policy for the internal
> shmem mount, applications that use shmem, such as the DRM GEM objects,
> can take advantage of mTHP before it's been configured through sysfs.
> 
> Signed-off-by: Maíra Canal <mcanal@igalia.com>
> ---
>   .../admin-guide/kernel-parameters.txt         |  7 ++
>   Documentation/admin-guide/mm/transhuge.rst    |  6 ++
>   mm/shmem.c                                    | 72 +++++++++++++------
>   3 files changed, 62 insertions(+), 23 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 1666576acc0e..acabb04d0dd4 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -6926,6 +6926,13 @@
>   			See Documentation/admin-guide/mm/transhuge.rst
>   			for more details.
>   
> +	transparent_hugepage_shmem= [KNL]
> +			Format: [always|within_size|advise|never|deny|force]
> +			Can be used to control the hugepage allocation policy for
> +			the internal shmem mount.
> +			See Documentation/admin-guide/mm/transhuge.rst
> +			for more details.
> +

LGTM, and it's consistent with the parameter for anon.

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

On 2024/10/30 20:58, Maíra Canal wrote:
> Add a new kernel command line to control the hugepage allocation policy
> for the internal shmem mount, ``transparent_hugepage_shmem``. The
> parameter is similar to ``transparent_hugepage`` and has the following
> format:
> 
> transparent_hugepage_shmem=<policy>
> 
> where ``<policy>`` is one of the seven valid policies available for
> shmem.
> 
> By configuring the default hugepage allocation policy for the internal
> shmem mount, applications that use shmem, such as the DRM GEM objects,
> can take advantage of mTHP before it's been configured through sysfs.
> 
> Signed-off-by: Maíra Canal <mcanal@igalia.com>

The changes look good to me. With the commit message update pointed out 
by Andrew, feel free to add:
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>