On Friday, January 1, 2021 10:17:08 PM EST Marco Nelissen wrote: > On Tue, Jul 28, 2020 at 10:52 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > On Thu, Jul 23, 2020 at 6:51 AM nerdopolis > > <bluescreen_avenger@xxxxxxxxxxx> wrote: > > > > > > On Thursday, July 16, 2020 1:03:52 PM EDT Amir Goldstein wrote: > > > > On Thu, Jul 16, 2020 at 6:09 AM nerdopolis > > > > <bluescreen_avenger@xxxxxxxxxxx> wrote: > > > > > > > > > > Hi > > > > > > > > > > A while back I opened up > > https://bugzilla.kernel.org/show_bug.cgi?id=195113 describing a > > documentation problem in > > > > > https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt > > but for whatever reason, it hasn't been seen. > > > > > > > > > > > > > > > The problem is that it says "The lower filesystem can be any > > filesystem supported by Linux" > > > > > however, this is not the case, as Linux supports vfat, and vfat > > doesn't work as a lower filesystem > > > > > > > > > > So there's no way to tell what filesystems are applicable for an > > overlay lowerfs, > > > > > and I don't think any existing userspace utilities can detect it. > > > > > > > > > > Could it be possible for the .txt file to be updated? > > > > > > > > > > > > > The way it works usually in this project is you can submit a patch to > > fix the > > > > problem: > > > > https://www.kernel.org/doc/html/v4.17/process/submitting-patches.html > > > > > > > > But if you don't want to go through that process, you can offer a text > > to > > > > fix documentation. > > > > > > > > But I myself cannot offer anything better than: > > > > "The lower filesystem can be one of many filesystem supported by > > Linux". > > > > > > > > I don't think that we want to start listing the supported filesystems > > in > > > > documentation. > > > > > > > > FWIW the description of upper fs isn't uptodate either. > > > > > > > > Thanks, > > > > Amir. > > > > > > > > > > > Hi. > > > > > > Yeah, that process might be cumbersome. I guess what you have is good. > > > Maybe "A wide range of filesystems supported by Linux can be the lower > > > filesystem, however, not all filesystems that are mountable by Linux > > have the > > > features needed for OverlayFS to work" > > > ? > > > > > > > That sounds good to me. > > > > CC the maintainer in case he wants to apply this documentation "patch" > > himself. > > > > Thanks, > > Amir. > > > > A documentation patch was submitted for this a few months ago ( > https://github.com/torvalds/linux/commit/58afaf5d605f091abf7491774e34fa29d4a1994c) > however I think the sentence "A read-only overlay of two read-only > filesystems may use any filesystem type." should also be removed or > rewritten, since a read-only vfat fs still can't be used in an overlay as > far as I can tell. > Yeah, testing on a read-only vfat filesystem as the lowerdir and it doesn't work Something to do with dentry's and ovl_dentry_weird. I don't think there's any way to determine that with a userspace utility or not.
