From 1c628004e0de0383a5a56facdb0bf28a54441b5f Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Thu, 22 Jan 2026 16:06:12 +0000 Subject: 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); 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 Link: https://lkml.kernel.org/r/fde00df6ff7fb8c4b42cc0defa5a4924c7a1943a.1769097829.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Suggested-by: Jason Gunthorpe Reviewed-by: Pedro Falcato Reviewed-by: Liam R. Howlett Cc: Baolin Wang Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zi Yan Cc: Damien Le Moal Cc: "Darrick J. Wong" Cc: Jarkko Sakkinen Cc: Yury Norov Cc: Chris Mason Signed-off-by: Andrew Morton --- include/linux/mm.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'include/linux') diff --git a/include/linux/mm.h b/include/linux/mm.h index 67b80f0ea225..d3d10c769d6f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2,6 +2,7 @@ #ifndef _LINUX_MM_H #define _LINUX_MM_H +#include #include #include #include @@ -1026,6 +1027,38 @@ 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 = 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; -- cgit v1.2.3