On Tue, Jun 20, 2017 at 12:39 PM, Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx> wrote: > On Monday, June 19, 2017 11:15:37 PM IST Amir Goldstein wrote: >> On Mon, Jun 19, 2017 at 6:22 PM, Chandan Rajendra >> <chandan@xxxxxxxxxxxxxxxxxx> wrote: >> > On an overlayfs instance having lower and upper dirs on the same >> > filesystem, stat(2) on a file residing on the lower dir will >> >> This is not what the patch should do. The patch should deal with !samefs case. >> >> > provide st_dev corresponding to the lower filesystem's bdev. Later, After >> > the lower file is copied-up, stat(2) on the file provides st_dev >> > corresponding to the overlayfs' pseudo device. Hence we have a mismatch >> > in the st_dev value that is provided to the userspace. >> >> All this is true, but you patch should not be bothering with constant st_dev >> over copy up. my patches do that. >> Your patch should provide the pseudo st_dev for lower, which my patch >> "relax same fs constrain for constant st_ino" needs to be able to use >> the lower (pseudo) dev as the constant st_dev across copy up. > > Ok. But we continue to use overlayfs' anon dev when reporting st_dev for > directories right? > Right... which means I was wrong about reporting the overlay st_dev for upper non-dir, because this could create st_dev/st_ino collision. Dir st_ino come from the overlay inode number pool and non-dir st_ino come from underlying fs. Easiest is to just return the real st_dev for pure upper, i.e.: + if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb->s_dev == dev) + return dev; + I am not sure that the benefits of allocating a pseudo dev also for upper layer are worth it. At the end of the day, a pure upper overlay object is really the same object as the underlying fs object and reporting a pseudo dev for those objects isn't going to help with du -x, so why bother. Amir. -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
