The patch titled Subject: mm: rename cpu_bitmap field to flexible_array has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-rename-cpu_bitmap-field-to-flexible_array.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Mathieu Desnoyers mathieu.desnoyers@efficios.com Subject: mm: rename cpu_bitmap field to flexible_array Date: Wed, 24 Dec 2025 12:33:57 -0500
The cpu_bitmap flexible array now contains more than just the cpu_bitmap. In preparation for changing the static mm_struct definitions to cover for the additional space required, change the cpu_bitmap type from "unsigned long" to "char", require an unsigned long alignment of the flexible array, and rename the field from "cpu_bitmap" to "flexible_array".
Introduce the MM_STRUCT_FLEXIBLE_ARRAY_INIT macro to statically initialize the flexible array. This covers the init_mm and efi_mm static definitions.
This is a preparation step for fixing the missing mm_cid size for static mm_struct definitions.
Link: https://lkml.kernel.org/r/20251224173358.647691-3-mathieu.desnoyers@efficios... Fixes: af7f588d8f73 ("sched: Introduce per-memory-map concurrency ID") Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Mark Brown broonie@kernel.org Cc: Aboorva Devarajan aboorvad@linux.ibm.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: Baolin Wang baolin.wang@linux.alibaba.com Cc: Christan K��nig christian.koenig@amd.com Cc: Christian Brauner brauner@kernel.org Cc: Christoph Lameter cl@linux.com Cc: David Hildenbrand david@redhat.com Cc: David Rientjes rientjes@google.com Cc: Dennis Zhou dennis@kernel.org Cc: Johannes Weiner hannes@cmpxchg.org Cc: "Liam R . Howlett" liam.howlett@oracle.com Cc: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: Martin Liu liumartin@google.com Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mateusz Guzik mjguzik@gmail.com Cc: Matthew Wilcox willy@infradead.org Cc: Miaohe Lin linmiaohe@huawei.com Cc: Michal Hocko mhocko@suse.com Cc: Mike Rapoport rppt@kernel.org Cc: "Paul E. McKenney" paulmck@kernel.org Cc: Roman Gushchin roman.gushchin@linux.dev Cc: SeongJae Park sj@kernel.org Cc: Shakeel Butt shakeel.butt@linux.dev Cc: Steven Rostedt rostedt@goodmis.org Cc: Suren Baghdasaryan surenb@google.com Cc: Sweet Tea Dorminy sweettea-kernel@dorminy.me Cc: Tejun Heo tj@kernel.org Cc: Vlastimil Babka vbabka@suse.cz Cc: Wei Yang richard.weiyang@gmail.com Cc: Yu Zhao yuzhao@google.com Cc: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
drivers/firmware/efi/efi.c | 2 +- include/linux/mm_types.h | 13 +++++++++---- mm/init-mm.c | 2 +- 3 files changed, 11 insertions(+), 6 deletions(-)
--- a/drivers/firmware/efi/efi.c~mm-rename-cpu_bitmap-field-to-flexible_array +++ a/drivers/firmware/efi/efi.c @@ -73,10 +73,10 @@ struct mm_struct efi_mm = { MMAP_LOCK_INITIALIZER(efi_mm) .page_table_lock = __SPIN_LOCK_UNLOCKED(efi_mm.page_table_lock), .mmlist = LIST_HEAD_INIT(efi_mm.mmlist), - .cpu_bitmap = { [BITS_TO_LONGS(NR_CPUS)] = 0}, #ifdef CONFIG_SCHED_MM_CID .mm_cid.lock = __RAW_SPIN_LOCK_UNLOCKED(efi_mm.mm_cid.lock), #endif + .flexible_array = MM_STRUCT_FLEXIBLE_ARRAY_INIT, };
struct workqueue_struct *efi_rts_wq; --- a/include/linux/mm_types.h~mm-rename-cpu_bitmap-field-to-flexible_array +++ a/include/linux/mm_types.h @@ -1329,7 +1329,7 @@ struct mm_struct { * The mm_cpumask needs to be at the end of mm_struct, because it * is dynamically sized based on nr_cpu_ids. */ - unsigned long cpu_bitmap[]; + char flexible_array[] __aligned(__alignof__(unsigned long)); };
/* Copy value to the first system word of mm flags, non-atomically. */ @@ -1366,19 +1366,24 @@ static inline void __mm_flags_set_mask_b MT_FLAGS_USE_RCU) extern struct mm_struct init_mm;
+#define MM_STRUCT_FLEXIBLE_ARRAY_INIT \ +{ \ + [0 ... sizeof(cpumask_t)-1] = 0 \ +} + /* Pointer magic because the dynamic array size confuses some compilers. */ static inline void mm_init_cpumask(struct mm_struct *mm) { unsigned long cpu_bitmap = (unsigned long)mm;
- cpu_bitmap += offsetof(struct mm_struct, cpu_bitmap); + cpu_bitmap += offsetof(struct mm_struct, flexible_array); cpumask_clear((struct cpumask *)cpu_bitmap); }
/* Future-safe accessor for struct mm_struct's cpu_vm_mask. */ static inline cpumask_t *mm_cpumask(struct mm_struct *mm) { - return (struct cpumask *)&mm->cpu_bitmap; + return (struct cpumask *)&mm->flexible_array; }
#ifdef CONFIG_LRU_GEN @@ -1469,7 +1474,7 @@ static inline cpumask_t *mm_cpus_allowed { unsigned long bitmap = (unsigned long)mm;
- bitmap += offsetof(struct mm_struct, cpu_bitmap); + bitmap += offsetof(struct mm_struct, flexible_array); /* Skip cpu_bitmap */ bitmap += cpumask_size(); return (struct cpumask *)bitmap; --- a/mm/init-mm.c~mm-rename-cpu_bitmap-field-to-flexible_array +++ a/mm/init-mm.c @@ -47,7 +47,7 @@ struct mm_struct init_mm = { #ifdef CONFIG_SCHED_MM_CID .mm_cid.lock = __RAW_SPIN_LOCK_UNLOCKED(init_mm.mm_cid.lock), #endif - .cpu_bitmap = CPU_BITS_NONE, + .flexible_array = MM_STRUCT_FLEXIBLE_ARRAY_INIT, INIT_MM_CONTEXT(init_mm) };
_
Patches currently in -mm which might be from mathieu.desnoyers@efficios.com are
mm-add-missing-static-initializer-for-init_mm-mm_cidlock.patch mm-rename-cpu_bitmap-field-to-flexible_array.patch mm-take-into-account-mm_cid-size-for-mm_struct-static-definitions.patch tsacct-skip-all-kernel-threads.patch lib-introduce-hierarchical-per-cpu-counters.patch mm-fix-oom-killer-inaccuracy-on-large-many-core-systems.patch mm-implement-precise-oom-killer-task-selection.patch