On Mon, Nov 07, 2022 at 08:40:02AM +0200, Amir Goldstein wrote: > On Mon, Nov 7, 2022 at 6:38 AM YoungJun.Park <her0gyugyu@xxxxxxxxx> wrote: > > > > Here is my curious scenario. > > > > 1. create a file on overlayfs. > > 2. delete a file on upper directory. > > 3. can see file contents using read sys call. (may file operations all success) > > 4. cannot remove, rename. it return -ESTALE error (may inode operations fail) > > > > I understand this scenario onto the code level. > > But I don't understand this situation itself. > > > > I found a overlay kernel docs and it comments > > Changes to underlying filesystems section > > > > ... > > 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. > > .... > > > > So here is my question (may it is suggestion) > > > > 1. underlying file system change is not allowed, then how about implementing shadow upper directory from user? > > 2. if read, write system call is allowed, how about changing remove, rename(and more I does not percept) operation success? > > > > What is your use case? > Why do you think this is worth spending time on? > If anything, we could implement revalidate to return ESTALE also from open > in such a case. > But again, why do you think that would matter? > > Thanks, > Amir. Thank you for replying. I develop antivirus scanner. When developing, I am confronted the situaion below. 1. make a docker container using overlayfs 2. our antivirus scanner detect on upperdir and remove it. 3. When I check container, the file contents can be read, buf file cannot be removed.(-ESTALE error) And as I think, the reason is upperdir is touchable. So it is better to hide upperdir. If it is hard to implement(or maybe there is a other reson that I don' know) it is better to make the situation is clear (file operation error, inode operations error or file operation success , inode operation success) Thank you again Amir. Best regards
