On 01/22, Oleg Nesterov wrote:
>
> Can't we simply add VM_NOHUGEPAGE into ->def_flags? See the (untested)
> patch below, on top of this series.
And perhaps the patch below makes sense as a separate change, I dunno.
------------------------------------------------------------------------------
Subject: [PATCH] mm: introduce VM_INIT_DEF_MASK
mm_init() always sets new_mm->def_flags = 0. We might want to
inherit some bits like we do with mm->flags.
Add the new VM_INIT_DEF_MASK (currently zero) which acts like
MMF_INIT_MASK for ->def_flags.
---
include/linux/mm.h | 2 ++
kernel/fork.c | 11 ++++++++---
2 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1cedd00..0a340c9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -167,6 +167,8 @@ extern unsigned int kobjsize(const void *objp);
*/
#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP)
+#define VM_INIT_DEF_MASK 0
+
/*
* mapping from the currently active vm_flags protection bits (the
* low four bits) to a page protection mask..
diff --git a/kernel/fork.c b/kernel/fork.c
index b84bef7..f6d020b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -529,8 +529,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm,
struct task_struct *p)
atomic_set(&mm->mm_count, 1);
init_rwsem(&mm->mmap_sem);
INIT_LIST_HEAD(&mm->mmlist);
- mm->flags = (current->mm) ?
- (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
mm->core_state = NULL;
atomic_long_set(&mm->nr_ptes, 0);
memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
@@ -538,8 +536,15 @@ static struct mm_struct *mm_init(struct mm_struct *mm,
struct task_struct *p)
mm_init_aio(mm);
mm_init_owner(mm, p);
- if (likely(!mm_alloc_pgd(mm))) {
+ if (current->mm) {
+ mm->flags = current->mm->flags & MMF_INIT_MASK;
+ mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
+ } else {
+ mm->flags = default_dump_filter;
mm->def_flags = 0;
+ }
+
+ if (likely(!mm_alloc_pgd(mm))) {
mmu_notifier_mm_init(mm);
return mm;
}
--
1.5.5.1
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