mm/vma: introduce and use vma_[flags_]can_merge()

Replace the open-coded VMA_SPECIAL_FLAGS check in the VMA merge logic with
two new functions vma_flags_can_merge() and vma_can_merge() and update the
merge logic to use the former.

This abstracts the check and expresses it in terms of the desired behaviour
rather than an arbitrary and confusing VMA flag.

This also lays the groundwork for making further improvements in VMA flag
usage.

Also update the userland VMA tests to reflect the change.

No functional change intended.

Link: https://lore.kernel.org/20261013-b4-mmap-prepare-vma-flag-sanify-v6-2-1aa3c9b139f9@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Gregory Price (Meta) <gourry@gourry.net>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Nico Pache <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Doug Gilbert <dgilbert@interlog.com>
Cc: James Bottomley <james.bottomley@hansenpartnership.com>
Cc: Martin K. Petersen <mkp@kernel.org>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Helge Deller <deller@gmx.de>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Harry Yoo <harry@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oupton@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Anup Patel <anup@brainfault.org>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Ying Huang <ying.huang@linux.alibaba.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Youngjun Park <youngjun.park@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Xu Xin <xu.xin@linux.dev>
Cc: Ihor Solodrai <ihor.solodrai@linux.dev>
Cc: Bert Karwatzki <spasswolf@web.de>

1 files changed, 21 insertions, 0 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 46a380aa1c84..10b5f08b8d21 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1614,6 +1614,27 @@ static inline bool vma_is_shared_maywrite(const struct vm_area_struct *vma)
 }
 
 /**
+ * vma_flags_can_merge() - Do the specified VMA flags permit the VMA to be
+ * merged with another?
+ * @flags: The VMA flags to test.
+ * Returns: true if the flags permit merging, false otherwise.
+ */
+static inline bool vma_flags_can_merge(const vma_flags_t *flags)
+{
+	return !vma_flags_test_any_mask(flags, VMA_SPECIAL_FLAGS);
+}
+
+/**
+ * vma_can_merge() - Do @vma's flags permit it to be merged with another VMA?
+ * @vma: The VMA to test.
+ * Returns: true if the flags permit merging, otherwise false.
+ */
+static inline bool vma_can_merge(const struct vm_area_struct *vma)
+{
+	return vma_flags_can_merge(&vma->flags);
+}
+
+/**
  * vma_kernel_pagesize - Default page size granularity for this VMA.
  * @vma: The user mapping.
  *