From: Lorenzo Stoakes (Oracle) Date: Fri, 20 Mar 2026 19:38:32 +0000 (+0000) Subject: mm: introduce vma_flags_count() and vma[_flags]_test_single_mask() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e79d1c500f52506b9eab39e81017e30b76f2864d;p=thirdparty%2Fkernel%2Flinux.git mm: introduce vma_flags_count() and vma[_flags]_test_single_mask() vma_flags_count() determines how many bits are set in VMA flags, using bitmap_weight(). vma_flags_test_single_mask() determines if a vma_flags_t set of flags contains a single flag specified as another vma_flags_t value, or if the sought flag mask is empty, it is defined to return false. This is useful when we want to declare a VMA flag as optionally a single flag in a mask or empty depending on kernel configuration. This allows us to have VM_NONE-like semantics when checking whether the flag is set. In a subsequent patch, we introduce the use of VMA_DROPPABLE of type vma_flags_t using precisely these semantics. It would be actively confusing to use vma_flags_test_any_single_mask() for this (and vma_flags_test_all_mask() is not correct to use here, as it trivially returns true when tested against an empty vma flags mask). We introduce vma_flags_count() to be able to assert that the compared flag mask is singular or empty, checked when CONFIG_DEBUG_VM is enabled. Also update the VMA tests as part of this change. Link: https://lkml.kernel.org/r/cd778dd02b9f2a01eb54d25a49dea8ec2ddf7753.1774034900.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Acked-by: Vlastimil Babka (SUSE) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Al Viro Cc: Anton Ivanov Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Chengming Zhou Cc: Christian Borntraeger Cc: Christian Brauner Cc: David Hildenbrand Cc: Dinh Nguyen Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Ingo Molnar Cc: Jan Kara Cc: Jann Horn Cc: Johannes Berg Cc: Kees Cook Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Ondrej Mosnacek Cc: Palmer Dabbelt Cc: Paul Moore Cc: Pedro Falcato Cc: Richard Weinberger Cc: Russell King Cc: Stephen Smalley Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: WANG Xuerui Cc: Will Deacon Cc: xu xin Signed-off-by: Andrew Morton --- diff --git a/include/linux/mm.h b/include/linux/mm.h index f704d7cf28714..de72382efac22 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1078,6 +1078,14 @@ static __always_inline vma_flags_t __mk_vma_flags(vma_flags_t flags, #define append_vma_flags(flags, ...) __mk_vma_flags(flags, \ COUNT_ARGS(__VA_ARGS__), (const vma_flag_t []){__VA_ARGS__}) +/* Calculates the number of set bits in the specified VMA flags. */ +static __always_inline int vma_flags_count(const vma_flags_t *flags) +{ + const unsigned long *bitmap = flags->__vma_flags; + + return bitmap_weight(bitmap, NUM_VMA_FLAG_BITS); +} + /* * Test whether a specific VMA flag is set, e.g.: * @@ -1153,6 +1161,26 @@ static __always_inline bool vma_flags_test_all_mask(const vma_flags_t *flags, #define vma_flags_test_all(flags, ...) \ vma_flags_test_all_mask(flags, mk_vma_flags(__VA_ARGS__)) +/* + * Helper to test that a flag mask of type vma_flags_t has a SINGLE flag set + * (returning false if flagmask has no flags set). + * + * This is defined to make the semantics clearer when testing an optionally + * defined VMA flags mask, e.g.: + * + * if (vma_flags_test_single_mask(&flags, VMA_DROPPABLE)) { ... } + * + * When VMA_DROPPABLE is defined if available, or set to EMPTY_VMA_FLAGS + * otherwise. + */ +static __always_inline bool vma_flags_test_single_mask(const vma_flags_t *flags, + vma_flags_t flagmask) +{ + VM_WARN_ON_ONCE(vma_flags_count(&flagmask) > 1); + + return vma_flags_test_any_mask(flags, flagmask); +} + /* Set each of the to_set flags in flags, non-atomically. */ static __always_inline void vma_flags_set_mask(vma_flags_t *flags, vma_flags_t to_set) @@ -1281,6 +1309,24 @@ static __always_inline bool vma_test_all_mask(const struct vm_area_struct *vma, #define vma_test_all(vma, ...) \ vma_test_all_mask(vma, mk_vma_flags(__VA_ARGS__)) +/* + * Helper to test that a flag mask of type vma_flags_t has a SINGLE flag set + * (returning false if flagmask has no flags set). + * + * This is useful when a flag needs to be either defined or not depending upon + * kernel configuration, e.g.: + * + * if (vma_test_single_mask(vma, VMA_DROPPABLE)) { ... } + * + * When VMA_DROPPABLE is defined if available, or set to EMPTY_VMA_FLAGS + * otherwise. + */ +static __always_inline bool +vma_test_single_mask(const struct vm_area_struct *vma, vma_flags_t flagmask) +{ + return vma_flags_test_single_mask(&vma->flags, flagmask); +} + /* * Helper to set all VMA flags in a VMA. * diff --git a/tools/testing/vma/include/custom.h b/tools/testing/vma/include/custom.h index 2c498e713fbda..b7d9eb0a44e41 100644 --- a/tools/testing/vma/include/custom.h +++ b/tools/testing/vma/include/custom.h @@ -15,12 +15,6 @@ extern unsigned long dac_mmap_min_addr; #define dac_mmap_min_addr 0UL #endif -#define VM_WARN_ON(_expr) (WARN_ON(_expr)) -#define VM_WARN_ON_ONCE(_expr) (WARN_ON_ONCE(_expr)) -#define VM_WARN_ON_VMG(_expr, _vmg) (WARN_ON(_expr)) -#define VM_BUG_ON(_expr) (BUG_ON(_expr)) -#define VM_BUG_ON_VMA(_expr, _vma) (BUG_ON(_expr)) - #define TASK_SIZE ((1ul << 47)-PAGE_SIZE) /* diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h index f9fe07a8a443a..244ee02dc21d3 100644 --- a/tools/testing/vma/include/dup.h +++ b/tools/testing/vma/include/dup.h @@ -905,6 +905,13 @@ static __always_inline vma_flags_t __mk_vma_flags(vma_flags_t flags, #define append_vma_flags(flags, ...) __mk_vma_flags(flags, \ COUNT_ARGS(__VA_ARGS__), (const vma_flag_t []){__VA_ARGS__}) +static __always_inline int vma_flags_count(const vma_flags_t *flags) +{ + const unsigned long *bitmap = flags->__vma_flags; + + return bitmap_weight(bitmap, NUM_VMA_FLAG_BITS); +} + static __always_inline bool vma_flags_test(const vma_flags_t *flags, vma_flag_t bit) { @@ -952,6 +959,14 @@ static __always_inline bool vma_flags_test_all_mask(const vma_flags_t *flags, #define vma_flags_test_all(flags, ...) \ vma_flags_test_all_mask(flags, mk_vma_flags(__VA_ARGS__)) +static __always_inline bool vma_flags_test_single_mask(const vma_flags_t *flags, + vma_flags_t flagmask) +{ + VM_WARN_ON_ONCE(vma_flags_count(&flagmask) > 1); + + return vma_flags_test_any_mask(flags, flagmask); +} + static __always_inline void vma_flags_set_mask(vma_flags_t *flags, vma_flags_t to_set) { unsigned long *bitmap = flags->__vma_flags; @@ -1031,6 +1046,12 @@ static __always_inline bool vma_test_all_mask(const struct vm_area_struct *vma, #define vma_test_all(vma, ...) \ vma_test_all_mask(vma, mk_vma_flags(__VA_ARGS__)) +static __always_inline bool +vma_test_single_mask(const struct vm_area_struct *vma, vma_flags_t flagmask) +{ + return vma_flags_test_single_mask(&vma->flags, flagmask); +} + static __always_inline void vma_set_flags_mask(struct vm_area_struct *vma, vma_flags_t flags) { diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h index 0e1121e2ef23e..e12ab2c80f950 100644 --- a/tools/testing/vma/vma_internal.h +++ b/tools/testing/vma/vma_internal.h @@ -51,6 +51,12 @@ typedef unsigned long pgprotval_t; typedef struct pgprot { pgprotval_t pgprot; } pgprot_t; typedef __bitwise unsigned int vm_fault_t; +#define VM_WARN_ON(_expr) (WARN_ON(_expr)) +#define VM_WARN_ON_ONCE(_expr) (WARN_ON_ONCE(_expr)) +#define VM_WARN_ON_VMG(_expr, _vmg) (WARN_ON(_expr)) +#define VM_BUG_ON(_expr) (BUG_ON(_expr)) +#define VM_BUG_ON_VMA(_expr, _vma) (BUG_ON(_expr)) + #include "include/stubs.h" #include "include/dup.h" #include "include/custom.h"