On Mon, Nov 16, 2015 at 4:09 AM, Yigal Korman <[email protected]> wrote: > DAX handling of COW faults has wrong locking sequence: > dax_fault does i_mmap_lock_read > do_cow_fault does i_mmap_unlock_write > > Ross's commit[1] missed a fix[2] that Kirill added to Matthew's > commit[3]. > > Original COW locking logic was introduced by Matthew here[4]. > > This should be applied to v4.3 as well. > > [1] 0f90cc6609c7 mm, dax: fix DAX deadlocks > [2] 52a2b53ffde6 mm, dax: use i_mmap_unlock_write() in do_cow_fault() > [3] 843172978bb9 dax: fix race between simultaneous faults > [4] 2e4cdab0584f mm: allow page fault handlers to perform the COW > > Signed-off-by: Yigal Korman <[email protected]> > > Cc: Stable Tree <[email protected]> > Cc: Boaz Harrosh <[email protected]> > Cc: Ross Zwisler <[email protected]> > Cc: Alexander Viro <[email protected]> > Cc: Dan Williams <[email protected]> > Cc: Dave Chinner <[email protected]> > Cc: Jan Kara <[email protected]> > Cc: "Kirill A. Shutemov" <[email protected]> > Cc: Matthew Wilcox <[email protected]> > --- > mm/memory.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index c716913..e5071af 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3015,9 +3015,9 @@ static int do_cow_fault(struct mm_struct *mm, struct > vm_area_struct *vma, > } else { > /* > * The fault handler has no page to lock, so it holds > - * i_mmap_lock for write to protect against truncate. > + * i_mmap_lock for read to protect against truncate. > */ > - i_mmap_unlock_write(vma->vm_file->f_mapping); > + i_mmap_unlock_read(vma->vm_file->f_mapping); > } > goto uncharge_out; > } > @@ -3031,9 +3031,9 @@ static int do_cow_fault(struct mm_struct *mm, struct > vm_area_struct *vma, > } else { > /* > * The fault handler has no page to lock, so it holds > - * i_mmap_lock for write to protect against truncate. > + * i_mmap_lock for read to protect against truncate. > */ > - i_mmap_unlock_write(vma->vm_file->f_mapping); > + i_mmap_unlock_read(vma->vm_file->f_mapping); > } > return ret; > uncharge_out:
Looks good to me. I'll include this with some other DAX fixes I have pending. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
