mm: rename cpu_bitmap field to flexible_array

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: af7f588d8f73 ("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>

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index f5ff6e84a9b7d8083b90a20fd617ad367c4b8889..17b5f3415465ed689358f27fbf2acef2e48cf24a 100644 (file)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -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;

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 42af2292951d4fb95e0838f31a06d84b806ef810..110b319a2ffb47fb1a166ac6a0ac953757681072 100644 (file)
--- a/include/linux/mm_types.h
+++ b/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_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;

diff --git a/mm/init-mm.c b/mm/init-mm.c
index a514f8ce47e3603414589782c2877722310227db..c5556bb9d5f01f5ce2fad072428a33f2bcf3d528 100644 (file)
--- a/mm/init-mm.c
+++ b/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)
 };