[Al Viro and linux-unionfs added to Cc] On Tue, May 19, 2015 at 11:30 PM, steve landiss <steve.landiss@xxxxxxxxx> wrote: > > On Tuesday, May 19, 2015 2:12 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > > > > > > On Mon, May 18, 2015 at 10:35 PM, steve landiss <steve.landiss@xxxxxxxxx> > > wrote: > > > >> A data consistency bug is demonstrated by the following program: > >> > >> - Pick a file from the lower layer that has never been written > >> - Open it twice once in O_RDONLY (fd1) and once in O_RDWR (fd2) > >> - Write to fd2, read from fd1 -> data inconsistency! > >> I understand why it happens, is there a fix planned for this? > > > > >> Not presently. > > > > This is a feature of both overlayfs and union-mounts. Aufs, a full > > union-filesystem doesn't suffer from this probelm. > > > > Is this causing a real-world problem, or is this purely theoretical? > yum fails right off the bat. Because it opens a file in read only, then > another process or thread writes to the file. > > Our build process in Docker does not work because of this, and I know of > many others that have this issue > > overlayfs fails to run container with a strange file checksum error · Issue > #10180 · docker/docker Okay, this is not easy to fix, but I wouldn't say impossible. I think it connects with the idea of revoking file descriptors. Except here we don't want to revoke, but replace on copy-up. But it might be easier to just to do the union-filesystem thing. Thanks, Miklos -- 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
