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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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3
tools/testing/vma/include/custom.h
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@@ -21,9 +21,6 @@ extern unsigned long dac_mmap_min_addr;
#define VM_BUG_ON(_expr) (BUG_ON(_expr))
#define VM_BUG_ON_VMA(_expr, _vma) (BUG_ON(_expr))
/* We hardcode this for now. */
#define sysctl_max_map_count 0x1000000UL
#define TASK_SIZE ((1ul << 47)-PAGE_SIZE)
/*