On Mon, Aug 24, 2020 at 3:02 PM Giuseppe Scrivano <gscrivan@xxxxxxxxxx> wrote: > > 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". Indeed. "Volatile" doesn't mean you can't use the data, just that the data may be lost completely in case of a crash (tmpfs analogue). Maybe just stick $(workdir)/work/incompat/volatile/donotremove in there to prevent misuse. Thanks, Miklos
