On Thu, Mar 28, 2013 at 09:03:16PM +0400, Konstantin Khlebnikov wrote:
> Naoya Horiguchi wrote:
> >Currently we fail to include any data on hugepages into coredump,
> >because VM_DONTDUMP is set on hugetlbfs's vma. This behavior was recently
> >introduced by commit 314e51b98 "mm: kill vma flag VM_RESERVED and
> >mm->reserved_vm counter". This looks to me a serious regression,
> >so let's fix it.
>
> That was introduced in my patch? Really?
> Here was VM_RESERVED and it had the same effect as VM_DONTDUMP. At least I thought so.
vma_dump_size() does like this (the diff is the one in 314e51b98):
static unsigned long vma_dump_size(struct vm_area_struct *vma,
unsigned long mm_flags)
{
#define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
/* always dump the vdso and vsyscall sections */
if (always_dump_vma(vma))
goto whole;
if (vma->vm_flags & VM_DONTDUMP)
return 0;
/* Hugetlb memory check */
if (vma->vm_flags & VM_HUGETLB) {
if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
goto whole;
if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
goto whole;
}
/* Do not dump I/O mapped devices or special mappings */
- if (vma->vm_flags & (VM_IO | VM_RESERVED))
+ if (vma->vm_flags & VM_IO)
return 0;
We have hugetlb memory check after VM_DONTDUMP check, so the following
changed the behavior.
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -110,7 +110,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
* way when do_mmap_pgoff unwinds (may be important on powerpc
* and ia64).
*/
- vma->vm_flags |= VM_HUGETLB | VM_RESERVED;
+ vma->vm_flags |= VM_HUGETLB | VM_DONTEXPAND | VM_DONTDUMP;
vma->vm_ops = &hugetlb_vm_ops;
if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
I think we don't have to set VM_DONTDUMP on hugetlbfs's vma.
Thanks,
Naoya
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