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From: Rusty Russell on 25 Jun 2010 09:10
Turns cpu_vm_mask into a bitmap, and truncate it to nr_cpu_ids if
CONFIG_CPUMASK_OFFSTACK is set.

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 <rusty(a)rustcorp.com.au>
Cc: Arnd Bergmann <arnd(a)arndb.de>
Cc: anton(a)samba.org
Cc: KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com>
Cc: Mike Travis <travis(a)sgi.com>
---
arch/x86/kernel/tboot.c | 2 +-
include/linux/mm_types.h | 26 +++++++++++++++++++++++---
kernel/fork.c | 6 +++---
mm/init-mm.c | 2 +-
4 files changed, 28 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;

@@ -310,9 +308,31 @@ struct mm_struct {
#ifdef CONFIG_MMU_NOTIFIER
struct mmu_notifier_mm *mmu_notifier_mm;
#endif
+
+ /* 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)
+{
+#ifdef CONFIG_CPUMASK_OFFSTACK
+ /*
+ * We restrict mm_struct allocations so cpu_vm_mask is only
+ * nr_cpu_ids long. cpu_vm_mask must be a NR_CPUS bitmap at
+ * 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) +
+ BITS_TO_LONGS(nr_cpu_ids) * sizeof(long);
+#else
+ return sizeof(struct mm_struct);
+#endif
+}

#endif /* _LINUX_MM_TYPES_H */
diff --git a/kernel/fork.c b/kernel/fork.c
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -505,7 +505,7 @@ 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;
@@ -656,7 +656,7 @@ 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;
@@ -1500,7 +1500,7 @@ 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
@@ -16,5 +16,5 @@ 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,
};

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Prev: ipmi: fix module param sparse warnings
Next: [PATCH 3/5] cpumask: select disabling obsolete cpumask functions on x86