]> git.karo-electronics.de Git - linux-beck.git/commit
mm: softdirty: respect VM_SOFTDIRTY in PTE holes
authorPeter Feiner <pfeiner@google.com>
Wed, 6 Aug 2014 23:08:09 +0000 (16:08 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 7 Aug 2014 01:01:22 +0000 (18:01 -0700)
commit68b5a652485682f67eacdee3deae640fb7845b63
tree727c13d01ca9c377d5936984c826c902a38b32be
parent3a91053aebb23205caf67927be00c54cef6424b3
mm: softdirty: respect VM_SOFTDIRTY in PTE holes

After a VMA is created with the VM_SOFTDIRTY flag set, /proc/pid/pagemap
should report that the VMA's virtual pages are soft-dirty until
VM_SOFTDIRTY is cleared (i.e., by the next write of "4" to
/proc/pid/clear_refs).  However, pagemap ignores the VM_SOFTDIRTY flag
for virtual addresses that fall in PTE holes (i.e., virtual addresses
that don't have a PMD, PUD, or PGD allocated yet).

To observe this bug, use mmap to create a VMA large enough such that
there's a good chance that the VMA will occupy an unused PMD, then test
the soft-dirty bit on its pages.  In practice, I found that a VMA that
covered a PMD's worth of address space was big enough.

This patch adds the necessary VMA lookup to the PTE hole callback in
/proc/pid/pagemap's page walk and sets soft-dirty according to the VMAs'
VM_SOFTDIRTY flag.

Signed-off-by: Peter Feiner <pfeiner@google.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/proc/task_mmu.c