---- 在 星期三, 2020-11-11 23:20:56 Amir Goldstein <amir73il@xxxxxxxxx> 撰写 ----
> On Wed, Nov 11, 2020 at 3:05 PM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote:
> >
> > ---- 在 星期日, 2020-11-08 22:03:03 Chengguang Xu <cgxu519@xxxxxxxxxxxx> 撰写 ----
> > > Overlayfs cannot be notified when mmapped area gets dirty,
> > > so we need to proactively mark inode dirty in ->mmap operation.
> > >
> > > Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
> > > ---
> > > fs/overlayfs/file.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> > > index efccb7c1f9bc..662252047fff 100644
> > > --- a/fs/overlayfs/file.c
> > > +++ b/fs/overlayfs/file.c
> > > @@ -486,6 +486,8 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
> > > /* Drop reference count from new vm_file value */
> > > fput(realfile);
> > > } else {
> > > + if (vma->vm_flags & (VM_SHARED|VM_MAYSHARE))
> >
> > Maybe it's better to mark dirty only having upper inode.
> >
>
> Yeh.
>
> And since mapping_map_writable() is only called if VM_SHARED flag
> is set (and not VM_MAYSHARE), we are not going to re-dirty an inode on
> account of VM_MAYSHARE alone, so I wonder why we need to mark it
> dirty here on account of VM_MAYSHARE?
>
Yeah, you are right. It just means the pages in this memory region can be mapped
by other process with shared+write mode and this is actually meaningless in our case.
So let's just ignore it. :-)
Thanks,
Chengguang
