Messages in this thread | | | Date | Fri, 05 Apr 2013 14:32:08 -0400 | From | KOSAKI Motohiro <> | Subject | Re: [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) |
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(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@jp.fujitsu.com>
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