(4/3/13 2:35 PM), 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.
I don't think this is enough explanations. Let's explain the code meaning
time to time order.
First, we had no madvice(DONTDUMP) nor coredump_filter(HUGETLB). then hugetlb
pages were never dumped.
Second, I added coredump_filter(HUGETLB). and then vm_dump_size became..
vm_dump_size()
{
/* Hugetlb memory check */
if (vma->vm_flags & VM_HUGETLB) {
..
goto whole;
}
if (vma->vm_flags & VM_RESERVED)
return 0;
The point is, hugetlb was checked before VM_RESERVED. i.e. hugetlb core dump ignored
VM_RESERVED. At this time, "if (vma->vm_flags & VM_HUGETLB)" statement don't need
return 0 because VM_RESERVED prevented to go into the subsequent flag checks.
Third, Jason added madvise(DONTDUMP). then vm_dump_size became...
vm_dump_size()
{
if (vma->vm_flags & VM_NODUMP)
return 0;
/* Hugetlb memory check */
if (vma->vm_flags & VM_HUGETLB) {
..
goto whole;
}
if (vma->vm_flags & VM_RESERVED)
return 0;
Look, VM_NODUMP and VM_RESERVED had similar and different meanings at this time.
Finally, Konstantin removed VM_RESERVED and hugetlb coredump behavior
has been changed.
Thus, patch [1/3] and [2/3] should be marked [stable for v3.6 or later].
Anyway, this patch is correct. Thank you!
Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
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