On Fri, Jan 05, 2018 at 05:47:36PM +0200, Amir Goldstein wrote: > On Fri, Jan 5, 2018 at 5:43 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > On Thu, Jan 04, 2018 at 06:40:01PM +0200, Amir Goldstein wrote: > >> Introduce the "verify" config, module and mount options. > >> > >> If the "verify" feature is enabled then overlay filesystems will use > >> the inodes index dir to verify layers consistency. > >> > >> It is possible to enable consistency verification by default during > >> build time with the OVERLAY_FS_VERIFY config option, during runtime > >> with the "verify=on" module option or on a filesystem instance basis > >> with the "verify=on" mount option. > >> > >> The "verify" feature will prevent multiple redirects to the same lower > >> dir and will prevent broken hardlinks from using the same inode number. > > > > So how does one end up with multiple redirects to same lower dir. > > > > Also what's the issue with broken hardlinks using same inode number. You > > mean lower and upper are on different fs and upper can use same inode > > number? With index=on, broken hardlink issue is taken care of so. So > > why would somebody use verify=on, which looks like will create index > > for all kind of files/dir. > > > > I have not followed this development and there is not much background > > in patch descrition or header patch, so asking all these basic questions. > > > > I have a ready answer for you :) > This is how it can happen and this is what can go wrong: > https://github.com/amir73il/xfstests/commit/f3c18125539660329195f142973ea620d6899418 > > The test duplicates a redirect dir offline with cp -a, but the > same thing can be done with a dir with origin. > In both cases, 'diff' will wrongly report that the files/dir are the same > even though they may differ (after being copied). So there are so many things a user can do with overlayfs offline. Should we need to put runtime checks for all these cases. I mean will fsck.overlay be a better place to catch these kind of anomalies. Secondly, verify=foo feels like a very generic option. Its not clear what all will it verify and will we continue to pile up more checks down the line under it. As a user, when should one use verify=on? Its not clear to me. Vivek > > 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 -- 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
