Message-ID: <2dbf01bf3538e13b2bd6125e6723165a94eaf06c.1768857200.git.lorenzo.stoakes@oracle.com>
Date: Mon, 19 Jan 2026 21:19:04 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jarkko Sakkinen <jarkko@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tursulin@...ulin.net>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>, Matthew Auld <matthew.auld@...el.com>,
        Matthew Brost <matthew.brost@...el.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        Benjamin LaHaise <bcrl@...ck.org>, Gao Xiang <xiang@...nel.org>,
        Chao Yu <chao@...nel.org>, Yue Hu <zbestahu@...il.com>,
        Jeffle Xu <jefflexu@...ux.alibaba.com>,
        Sandeep Dhavale <dhavale@...gle.com>,
        Hongbo Li <lihongbo22@...wei.com>, Chunhai Guo <guochunhai@...o.com>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Muchun Song <muchun.song@...ux.dev>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...nel.org>,
        Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
        Mike Marshall <hubcap@...ibond.com>,
        Martin Brandenburg <martin@...ibond.com>,
        Tony Luck <tony.luck@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Dave Martin <Dave.Martin@....com>, James Morse <james.morse@....com>,
        Babu Moger <babu.moger@....com>, Carlos Maiolino <cem@...nel.org>,
        Damien Le Moal <dlemoal@...nel.org>,
        Naohiro Aota <naohiro.aota@....com>,
        Johannes Thumshirn <jth@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Hugh Dickins <hughd@...gle.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>, Zi Yan <ziy@...dia.com>,
        Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
        Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
        Lance Yang <lance.yang@...ux.dev>, Jann Horn <jannh@...gle.com>,
        Pedro Falcato <pfalcato@...e.de>, David Howells <dhowells@...hat.com>,
        Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Yury Norov <yury.norov@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev,
        linux-cxl@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-fsdevel@...r.kernel.org,
        linux-aio@...ck.org, linux-erofs@...ts.ozlabs.org,
        linux-ext4@...r.kernel.org, linux-mm@...ck.org, ntfs3@...ts.linux.dev,
        devel@...ts.orangefs.org, linux-xfs@...r.kernel.org,
        keyrings@...r.kernel.org, linux-security-module@...r.kernel.org,
        Jason Gunthorpe <jgg@...dia.com>
Subject: [PATCH RESEND 02/12] mm: add mk_vma_flags() bitmap flag macro helper

This patch introduces the mk_vma_flags() macro helper to allow easy
manipulation of VMA flags utilising the new bitmap representation
implemented of VMA flags defined by the vma_flags_t type.

It is a variadic macro which provides a bitwise-or'd representation of all
of each individual VMA flag specified.

Note that, while we maintain VM_xxx flags for backwards compatibility until
the conversion is complete, we define VMA flags of type vma_flag_t using
VMA_xxx_BIT to avoid confusing the two.

This helper macro therefore can be used thusly:

vma_flags_t flags = mk_vma_flags(VMA_READ_BIT, VMA_WRITE_BIT);

We allow for up to 5 flags to specified at a time which should accommodate
all current kernel uses of combined VMA flags.

Testing has demonstrated that the compiler optimises this code such that it
generates the same assembly utilising this macro as it does if the flags
were specified manually, for instance:

vma_flags_t get_flags(void)
{
	return mk_vma_flags(VMA_READ_BIT, VMA_WRITE_BIT, VMA_EXEC_BIT);
}

Generates the same code as:

vma_flags_t get_flags(void)
{
	vma_flags_t flags;

	vma_flags_clear_all(&flags);
	vma_flag_set(&flags, VMA_READ_BIT);
	vma_flag_set(&flags, VMA_WRITE_BIT);
	vma_flag_set(&flags, VMA_EXEC_BIT);

	return flags;
}

And:

vma_flags_t get_flags(void)
{
	vma_flags_t flags;
	unsigned long *bitmap = ACCESS_PRIVATE(&flags, __vma_flags);

	*bitmap = 1UL << (__force int)VMA_READ_BIT;
	*bitmap |= 1UL << (__force int)VMA_WRITE_BIT;
	*bitmap |= 1UL << (__force int)VMA_EXEC_BIT;

	return flags;
}

That is:

get_flags:
        movl    $7, %eax
        ret

Suggested-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 include/linux/mm.h | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 52bf141fc018..c2c5b7328c21 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2,6 +2,7 @@
 #ifndef _LINUX_MM_H
 #define _LINUX_MM_H

+#include <linux/args.h>
 #include <linux/errno.h>
 #include <linux/mmdebug.h>
 #include <linux/gfp.h>
@@ -1029,6 +1030,38 @@ static inline bool vma_test_atomic_flag(struct vm_area_struct *vma, vma_flag_t b
 	return false;
 }

+/* Set an individual VMA flag in flags, non-atomically. */
+static inline void vma_flag_set(vma_flags_t *flags, vma_flag_t bit)
+{
+	unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);
+
+	__set_bit((__force int)bit, bitmap);
+}
+
+static inline vma_flags_t __mk_vma_flags(size_t count, const vma_flag_t *bits)
+{
+	vma_flags_t flags;
+	int i;
+
+	vma_flags_clear_all(&flags);
+	for (i = 0; i < count; i++)
+		vma_flag_set(&flags, bits[i]);
+	return flags;
+}
+
+/*
+ * Helper macro which bitwise-or combines the specified input flags into a
+ * vma_flags_t bitmap value. E.g.:
+ *
+ * vma_flags_t flags = mk_vma_flags(VMA_IO_BIT, VMA_PFNMAP_BIT,
+ * 		VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT);
+ *
+ * The compiler cleverly optimises away all of the work and this ends up being
+ * equivalent to aggregating the values manually.
+ */
+#define mk_vma_flags(...) __mk_vma_flags(COUNT_ARGS(__VA_ARGS__), \
+					 (const vma_flag_t []){__VA_ARGS__})
+
 static inline void vma_set_anonymous(struct vm_area_struct *vma)
 {
 	vma->vm_ops = NULL;
--
2.52.0

Powered by blists - more mailing lists