Messages in this thread | | | From | Amir Goldstein <> | Date | Fri, 21 Oct 2016 16:18:26 +0300 | Subject | Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up |
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On Fri, Oct 21, 2016 at 12:30 PM, Miklos Szeredi <miklos@szeredi.hu> wrote: > On Fri, Oct 21, 2016 at 11:13 AM, Amir Goldstein <amir73il@gmail.com> wrote: > >> I think it would be a good idea in general to stabilize the overlay ino/dev >> throughout copy-up, same as Miklos suggested to do for directories, to >> all files: >> pure upper uses upper ino + overlayfs dev >> non-pure upper uses lower ino + overlayfs dev > > Making st_ino, st_dev and d_ino behave consistently would be the next big step. > > The above scheme only works if lower and upper are on the same > filesystem. Otherwise there can be collisions between the lower and > upper inode numbers. Perhaps you meant: > > - pure upper uses upper ino + upper dev > - non-pure upper uses lower ino + overlayfs dev > > It works for the single lower layer case, but again breaks if there > are multiple lower layers. And d_ino in a merged directory could > still get us into trouble. And find -xdev would not do what you'd > expect with a "normal" filesystem. > > So there doesn't appear to be any easy solutions to this... >
Not for the general case there isn't, but I was actually thinking of the docker case and there is a lot that can be done for the use case of lower and upper on the same fs to make overlayfs more compliant. Since it's quite a common use case, perhaps its worth the special treatment.
Amir.
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