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mm: abstract reading sysctl_max_map_count, and READ_ONCE()

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Concurrent reads and writes of sysctl_max_map_count are possible, so we
should READ_ONCE() and WRITE_ONCE().

The sysctl procfs logic already enforces WRITE_ONCE(), so abstract the
read side with get_sysctl_max_map_count().

While we're here, also move the field to mm/internal.h and add the getter
there since only mm interacts with it, there's no need for anybody else to
have access.

Finally, update the VMA userland tests to reflect the change.

Link: https://lkml.kernel.org/r/0715259eb37cbdfde4f9e5db92a20ec7110a1ce5.1773249037.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Cc: Jann Horn <jannh@google.com>
Cc: Jianzhou Zhao <luckd0g@163.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes (Oracle)
2026-03-11 17:24:37 +00:00
committed by Andrew Morton
parent 9b9b8d4aeb
commit 2d1e54aab6
9 changed files with 24 additions and 12 deletions
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9
tools/testing/vma/include/dup.h
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@@ -419,6 +419,9 @@ struct vma_iterator {
#define EMPTY_VMA_FLAGS ((vma_flags_t){ })
#define MAPCOUNT_ELF_CORE_MARGIN (5)
#define DEFAULT_MAX_MAP_COUNT (USHRT_MAX - MAPCOUNT_ELF_CORE_MARGIN)
/* What action should be taken after an .mmap_prepare call is complete? */
enum mmap_action_type {
MMAP_NOTHING, /* Mapping is complete, no further action. */
@@ -1342,3 +1345,9 @@ static inline void vma_set_file(struct vm_area_struct *vma, struct file *file)
swap(vma->vm_file, file);
fput(file);
}
extern int sysctl_max_map_count;
static inline int get_sysctl_max_map_count(void)
{
return READ_ONCE(sysctl_max_map_count);
}