On Thu, Jun 6, 2019 at 8:54 AM Eric Biggers [off-list ref] wrote:

This is a redesigned version of the fs-verity patchset, implementing
Ted's suggestion to build the Merkle tree in the kernel
(https://lore.kernel.org/linux-fsdevel/20190207031101.GA7387@mit.edu/ (local)).
This greatly simplifies the UAPI, since the verity metadata no longer
needs to be transferred to the kernel.

Interfaces look sane to me. My only real concern is whether it would
make sense to make the FS_IOC_ENABLE_VERITY ioctl be something that
could be done incrementally, since the way it is done now it looks
like any random user could create a big file and then do the
FS_IOC_ENABLE_VERITY to make the kernel do a _very_ expensive
operation.

Yes, I see the

+               if (fatal_signal_pending(current))
+                       return -EINTR;
+               cond_resched();

in there, so it's not like it's some entirely unkillable thing, and
maybe we don't care as a result. But maybe the ioctl interface could
be fundamentally restartable?

If that was already considered and people just went "too complex", never mind.

               Linus