The patch titled
Subject: mm: Loosen MADV_NOHUGEPAGE to enable Qemu postcopy on s390
has been added to the -mm tree. Its filename is
mm-loosen-madv_nohugepage-to-enable-qemu-postcopy-on-s390.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-loosen-madv_nohugepage-to-enable-qemu-postcopy-on-s390.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-loosen-madv_nohugepage-to-enable-qemu-postcopy-on-s390.patch
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------------------------------------------------------
From: "Jason J. Herne" <jjherne@xxxxxxxxxxxxxxxxxx>
Subject: mm: Loosen MADV_NOHUGEPAGE to enable Qemu postcopy on s390
MADV_NOHUGEPAGE processing is too restrictive. kvm already disables
hugepage but hugepage_madvise() takes the error path when we ask to turn
on the MADV_NOHUGEPAGE bit and the bit is already on. This causes Qemu's
new postcopy migration feature to fail on s390 because its first action is
to madvise the guest address space as NOHUGEPAGE. This patch modifies the
code so that the operation succeeds without error now.
For consistency reasons do the same for MADV_HUGEPAGE.
Signed-off-by: Jason J. Herne <jjherne@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN mm/huge_memory.c~mm-loosen-madv_nohugepage-to-enable-qemu-postcopy-on-s390 mm/huge_memory.c
--- a/mm/huge_memory.c~mm-loosen-madv_nohugepage-to-enable-qemu-postcopy-on-s390
+++ a/mm/huge_memory.c
@@ -2009,7 +2009,7 @@ int hugepage_madvise(struct vm_area_stru
/*
* Be somewhat over-protective like KSM for now!
*/
- if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
+ if (*vm_flags & VM_NO_THP)
return -EINVAL;
*vm_flags &= ~VM_NOHUGEPAGE;
*vm_flags |= VM_HUGEPAGE;
@@ -2025,7 +2025,7 @@ int hugepage_madvise(struct vm_area_stru
/*
* Be somewhat over-protective like KSM for now!
*/
- if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
+ if (*vm_flags & VM_NO_THP)
return -EINVAL;
*vm_flags &= ~VM_HUGEPAGE;
*vm_flags |= VM_NOHUGEPAGE;
_
Patches currently in -mm which might be from jjherne@xxxxxxxxxxxxxxxxxx are
mm-loosen-madv_nohugepage-to-enable-qemu-postcopy-on-s390.patch
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