On Wed, Oct 02, 2019 at 03:47:24PM +0200, Thomas Hellström (VMware) wrote: > From: Thomas Hellstrom <thellstrom@xxxxxxxxxx> > > The caller needs to make sure that the vma is not torn down during the > lock operation and can also use the i_mmap_rwsem for file-backed vmas. > Remove the BUG_ON. We could, as an alternative, add a test that either > vma->vm_mm->mmap_sem or vma->vm_file->f_mapping->i_mmap_rwsem are held. > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Cc: Will Deacon <will.deacon@xxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Rik van Riel <riel@xxxxxxxxxxx> > Cc: Minchan Kim <minchan@xxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: Huang Ying <ying.huang@xxxxxxxxx> > Cc: Jérôme Glisse <jglisse@xxxxxxxxxx> > Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> > Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx> The patch looks good to me: Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> But I looked at usage at pagewalk.c and it is inconsitent. The walker takes ptl before calling ->pud_entry(), but not for ->pmd_entry(). It should be fixed: do not take the lock before ->pud_entry(). The callback must take care of it. Looks like we have single ->pud_entry() implementation the whole kernel. It should be trivial to fix. Could you do this? -- Kirill A. Shutemov
