From: Rusty Russell Subject: cpumask: truncate mm_struct.cpu_vm_mask for CONFIG_CPUMASK_OFFSTACK Turns cpu_vm_mask into a bitmap, and truncate it to cpumask_size(): if CONFIG_CPUMASK_OFFSTACK is set, this will reflect nr_cpu_ids not NR_CPUS. I do this rather than the classic [0] dangling array trick, because of init_mm, which is static and widely referenced. Signed-off-by: Rusty Russell Cc: Arnd Bergmann Cc: anton@samba.org Cc: KOSAKI Motohiro Cc: Mike Travis --- arch/x86/kernel/tboot.c | 2 +- include/linux/mm_types.h | 21 ++++++++++++++++++--- kernel/fork.c | 6 +++--- mm/init-mm.c | 2 +- 4 files changed, 23 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c --- a/arch/x86/kernel/tboot.c +++ b/arch/x86/kernel/tboot.c @@ -110,7 +110,7 @@ static struct mm_struct tboot_mm = { .mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem), .page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock), .mmlist = LIST_HEAD_INIT(init_mm.mmlist), - .cpu_vm_mask = CPU_MASK_ALL, + .cpu_vm_mask = CPU_BITS_ALL, }; static inline void switch_to_tboot_pt(void) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -265,8 +265,6 @@ struct mm_struct { struct linux_binfmt *binfmt; - cpumask_t cpu_vm_mask; - /* Architecture-specific MM context */ mm_context_t context; @@ -312,9 +310,26 @@ struct mm_struct { #endif /* How many tasks sharing this mm are OOM_DISABLE */ atomic_t oom_disable_count; + + /* This has to go at the end: if CONFIG_CPUMASK_OFFSTACK=y, only + * nr_cpu_ids bits will actually be allocated. */ + DECLARE_BITMAP(cpu_vm_mask, CONFIG_NR_CPUS); }; /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */ -#define mm_cpumask(mm) (&(mm)->cpu_vm_mask) +#define mm_cpumask(mm) (to_cpumask((mm)->cpu_vm_mask)) +static inline size_t mm_struct_size(void) +{ + /* + * For CONFIG_CPUMASK_OFFSTACK we reduce mm_struct allocations as + * cpu_vm_mask only needs cpumask_size() bytes. cpu_vm_mask must be + * a NR_CPUS bitmap at the end for this to work. + */ + BUILD_BUG_ON(offsetof(struct mm_struct, cpu_vm_mask) + + BITS_TO_LONGS(CONFIG_NR_CPUS)*sizeof(long) + != sizeof(struct mm_struct)); + return offsetof(struct mm_struct, cpu_vm_mask) + cpumask_size(); +} + #endif /* _LINUX_MM_TYPES_H */ diff --git a/kernel/fork.c b/kernel/fork.c --- a/kernel/fork.c +++ b/kernel/fork.c @@ -510,7 +510,7 @@ struct mm_struct * mm_alloc(void) mm = allocate_mm(); if (mm) { - memset(mm, 0, sizeof(*mm)); + memset(mm, 0, mm_struct_size()); mm = mm_init(mm, current); } return mm; @@ -661,7 +661,7 @@ struct mm_struct *dup_mm(struct task_str if (!mm) goto fail_nomem; - memcpy(mm, oldmm, sizeof(*mm)); + memcpy(mm, oldmm, mm_struct_size()); /* Initializing for Swap token stuff */ mm->token_priority = 0; @@ -1515,7 +1515,7 @@ void __init proc_caches_init(void) sizeof(struct fs_struct), 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); mm_cachep = kmem_cache_create("mm_struct", - sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, + mm_struct_size(), ARCH_MIN_MMSTRUCT_ALIGN, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); mmap_init(); diff --git a/mm/init-mm.c b/mm/init-mm.c --- a/mm/init-mm.c +++ b/mm/init-mm.c @@ -21,6 +21,6 @@ struct mm_struct init_mm = { .mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem), .page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock), .mmlist = LIST_HEAD_INIT(init_mm.mmlist), - .cpu_vm_mask = CPU_MASK_ALL, + .cpu_vm_mask = CPU_BITS_ALL, INIT_MM_CONTEXT(init_mm) };