On Thu, May 18, 2017 at 2:08 AM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > The other thing I wanted to ask and it doesn't require you looking at > any code is how to handle backward compat of mount behavior when > workdir is reused for mount with a different upperdir. > > The use case may seem odd, but I already ran into it with unionmount > testsuite ./run --ov=1 and with xfstest overlay/014. > Maybe those are the only examples in the world, but maybe not... > > The problem is that if workdir/index contains hardlinks to a past upper > which has been rotated to lower, bad things can happen on copy up. > What I did so far is to store origin fh of upper root in index dir. > Mount forces read-only if index dir origin does not match upper root dir. > > So with current WIP the behavior is that ./run --ov=1 fails after > rotating upper: > > overlayfs: failed to verify origin dir (ino=19025, ret=-116) - were > layers copied? > overlayfs: failed to create directory /upper/work/index (errno: 17); > mounting read-only > ./run --rename /mnt/a/no_foo104 /mnt/a/no_foo105 > /mnt/a/no_foo104: Unexpected error: Read-only file system > > It's easy to fix the testsuite, but it is doing something that was legal before > (provide the same workdir option with different upperdir options) and now > it fails. > > The alternative is to blow away the index dir and recreate it when mounting > with an unverified upperdir. This will work fine for the testsuite, but not for > the obscure users out there using the same workdir to mount with few different > upperdir (not at the same time) - do we care? > > I guess the best is to blow away index dir unless user explicitly opted-in > to not blow it away, e.g. by using mount option indexdir= in place of workdir= > (mutually excl.). > Actually, it may make sense to have -o verify_lower control this behavior. Specifying -o verify_lower clearly states the intention of the user to mount overlay layers that were not copied, therefore it makes sense to fail rw mount. OTHO, with this wider meaning, I no longer like the name 'verify_lower', for 2 reasons: 1. It is only used to verify directories 2. It is now also used to verify upper root dir So how about 'verify_dir'/'verify_fh'/'verify_origin'? -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
