On Sun 25-10-20 11:41:14, Chengguang Xu wrote:
> 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 | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index efccb7c1f9bc..cd6fcdfd81a9 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -486,6 +486,10 @@ 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) &&
> + vma->vm_flags & (VM_WRITE|VM_MAYWRITE))
> + ovl_mark_inode_dirty(file_inode(file));
> +
But does this work reliably? I mean once writeback runs, your inode (as
well as upper inode) is cleaned. Then a page fault comes so file has dirty
pages again and would need flushing but overlayfs inode stays clean? Am I
missing something?
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
