---- 在 星期四, 2020-11-05 16:07:26 Amir Goldstein <amir73il@xxxxxxxxx> 撰写 ---- > On Thu, Nov 5, 2020 at 6:39 AM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote: > > > > Hello, > > > > I have a question about opening file of underlying filesystem in overlayfs, > > > > why we use overlayfs' path(vfsmount/dentry) struct for underlying fs' file > > > > in ovl_open_realfile()? Is it by design? > > Sure. open_with_fake_path() is only used by overlayfs. > > IIRC, one of the reasons was to display the user expected path in > /proc/<pid>/maps. > There may have been other reasons. > So if we do the mmap with overlayfs' own page cache, then we don't have to use pseudo path for the reason above, right? Actually, the background is I'm trying to implement overlayfs' page cache for fixing mmap rorw issue. The reason why asking this is I need to open a writeback file which is used for syncing dirty data from overlayfs' own page cache to upper inode. However, if I use the pseudo path just like current opening behavior, the writeback file will hold a reference of vfsmount of overlayfs and it will cause umount fail with -EBUSY. So I want to open a writeback file with correct underlying path struct but not sure if there is any unexpected side effect. Any suggestion? Thanks, Chengguang
