diff options
author | Peter Feiner <pfeiner@google.com> | 2014-08-07 01:08:09 +0200 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-07 03:01:22 +0200 |
commit | 68b5a652485682f67eacdee3deae640fb7845b63 (patch) | |
tree | 727c13d01ca9c377d5936984c826c902a38b32be /fs/proc/task_mmu.c | |
parent | mm: mark fault_around_bytes __read_mostly (diff) | |
download | linux-68b5a652485682f67eacdee3deae640fb7845b63.tar.xz linux-68b5a652485682f67eacdee3deae640fb7845b63.zip |
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>
Diffstat (limited to '')
-rw-r--r-- | fs/proc/task_mmu.c | 27 |
1 files changed, 21 insertions, 6 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index cfa63ee92c96..dfc791c42d64 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -925,15 +925,30 @@ static int pagemap_pte_hole(unsigned long start, unsigned long end, struct mm_walk *walk) { struct pagemapread *pm = walk->private; - unsigned long addr; + unsigned long addr = start; int err = 0; - pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2)); - for (addr = start; addr < end; addr += PAGE_SIZE) { - err = add_to_pagemap(addr, &pme, pm); - if (err) - break; + while (addr < end) { + struct vm_area_struct *vma = find_vma(walk->mm, addr); + pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2)); + unsigned long vm_end; + + if (!vma) { + vm_end = end; + } else { + vm_end = min(end, vma->vm_end); + if (vma->vm_flags & VM_SOFTDIRTY) + pme.pme |= PM_STATUS2(pm->v2, __PM_SOFT_DIRTY); + } + + for (; addr < vm_end; addr += PAGE_SIZE) { + err = add_to_pagemap(addr, &pme, pm); + if (err) + goto out; + } } + +out: return err; } |