Messages in this thread | | | Date | Mon, 16 Nov 2015 10:15:56 -0800 | Subject | Re: [PATCH] mm, dax: fix DAX deadlocks (COW fault) | From | Dan Williams <> |
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On Mon, Nov 16, 2015 at 4:09 AM, Yigal Korman <yigal@plexistor.com> 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 <yigal@plexistor.com> > > Cc: Stable Tree <stable@vger.kernel.org> > Cc: Boaz Harrosh <boaz@plexistor.com> > Cc: Ross Zwisler <ross.zwisler@linux.intel.com> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Dave Chinner <dchinner@redhat.com> > Cc: Jan Kara <jack@suse.com> > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Cc: Matthew Wilcox <matthew.r.wilcox@intel.com> > --- > 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.
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