Amir Goldstein <amir73il@xxxxxxxxx> writes: > On Mon, Aug 24, 2020 at 2:39 PM Giuseppe Scrivano <gscrivan@xxxxxxxxxx> wrote: >> >> Hi Amir, >> >> Amir Goldstein <amir73il@xxxxxxxxx> writes: >> >> > On Mon, Aug 24, 2020 at 11:15 AM Miklos Szeredi <miklos@xxxxxxxxxx> wrote: >> >> >> >> On Sat, Aug 22, 2020 at 11:27 AM Giuseppe Scrivano <gscrivan@xxxxxxxxxx> wrote: >> >> > >> >> > Vivek Goyal <vgoyal@xxxxxxxxxx> writes: >> >> > >> >> > > Container folks are complaining that dnf/yum issues too many sync while >> >> > > installing packages and this slows down the image build. Build >> >> > > requirement is such that they don't care if a node goes down while >> >> > > build was still going on. In that case, they will simply throw away >> >> > > unfinished layer and start new build. So they don't care about syncing >> >> > > intermediate state to the disk and hence don't want to pay the price >> >> > > associated with sync. >> >> > > >> >> >> >> [...] >> >> >> >> > Ping. >> >> > >> >> > Is there anything holding this patch? >> >> >> >> Not sure what happened with protection against mounting a volatile >> >> overlay twice, I don't see that in the patch. >> > >> > Do you mean protection only for new kernels or old kernels as well? >> > >> > The latter can be achieved by using $workdir/volatile/ as upperdir >> > instead of $upperdir. >> > Or maybe even use $workdir/work/incompat/volatile/upper, so if older >> > kernel tries to re-use that $workdir, it will fail to mount rw with error: >> > >> > overlayfs: cleanup of 'incompat/volatile' failed (-39) >> > >> > If we agree to that, then upperdir= should not be provided at all when >> > specifying "volatile". >> >> in this case, what does a program need to do to remount the overlay more >> than once? Is it enough to just delete a file? >> > > Do you mean re-mount while forgetting all changes to previous "volatile" > mount? no, without forgetting them. The original idea was to have a way to disable any sync operation in the overlay file system and let the upper layers handle it. IOW, mount volatile overlay+umount overlay+syncfs upper dir must still be considered safe. If we want to make it safer and disallow remounting the same workdir+upperdir by default when "volatile" is used, that is fine; but I think there should still be a way to say "I know what I am doing, just remount it". Regards, Giuseppe
