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?
Thanks,
Amir.
