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mm: rename cpu_bitmap field to flexible_array

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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.com
Fixes: af7f588d8f ("sched: Introduce per-memory-map concurrency ID")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Thomas Gleixner <tglx@kernel.org>
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 König <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>
This commit is contained in:
Mathieu Desnoyers 2025-12-24 12:33:57 -05:00 • committed by Andrew Morton
parent 12a6ddfc76
commit 6ac433f8b2
3 changed files with 11 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

2
drivers/firmware/efi/efi.c
View file

@ -74,10 +74,10 @@ struct mm_struct efi_mm = {
.page_table_lock = __SPIN_LOCK_UNLOCKED(efi_mm.page_table_lock),
.mmlist = LIST_HEAD_INIT(efi_mm.mmlist),
.user_ns = &init_user_ns,
.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;

13
include/linux/mm_types.h
View file

@ -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_bits_word(struct mm_struct *mm,
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(struct mm_struct *mm)
{
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;

2
mm/init-mm.c
View file

@ -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)
};