On Wed, Jul 05, 2017 at 02:17:41PM +0300, Amir Goldstein wrote: > On Wed, Jul 5, 2017 at 1:09 PM, Eryu Guan <eguan@xxxxxxxxxx> wrote: > > On Tue, Jul 04, 2017 at 02:40:34PM +0300, Amir Goldstein wrote: > >> nlink of overlay inode could be dropped indefinety by adding > >> un-accounted lower hardlinks underneath a mounted overlay and > >> trying to remove them. > > > > Sorry, I didn't quite follow the hardlink patches, could you please > > describe what is "accounted/un-accounted" hardlinks and the expected > > behavior in commit log? And what does "indefinety" mean? I couldn't find > > it in dictionary. > > > > Try the typos dictionary ;) I meant indefinitely > > I will try to explain better in change log, but here is the full story: > > The simplest way to understand this test is this: > Imagine that you have a tool (e.g. xfs_db) with which > you can add hardlinks, without changing the value of nlink > stored on-disk for the inode. This is exactly what this test does when > it adds lower hardlinks underneath a mounted overlay. > > Overlayfs assumes that the lower layer files are not modified > underneath it and if they do, the documentation says: > "Changes to the underlying filesystems while part of a mounted overlay > filesystem are not allowed. If the underlying filesystem is changed, > the behavior of the overlay is undefined, though it will not result in > a crash or deadlock." > > As far as I know, this test cannot crash the kernel, but it does trigger > the WARN_ON in drop_link() when nlink drops below zero, so it's not > nice behavior and could possibly results in worse outcomes. I understand now, thanks! Yeah, it's good to have these in commit log or comments :) Thanks, Eryu -- 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
