Re: [Libguestfs] [nbdkit PATCH v2 07/24] sh: Implement .cache script callback

On Wed, May 15, 2019 at 10:57:57PM -0500, Eric Blake wrote: > It's easy to expose new callbacks to sh plugins, by borrowing > tri-state code from can_fua. It's possible that nbdkit emulate will > actually work well (in our example.sh script, the kernel caching a > pread from one dd invocation may indeed speed up the next access), but > for the sake of the example, I demonstrated advertising a no-op > handler. > > The shell plugin, coupled with Rich's work on libnbd as a client-side > library for actually exercising calls to NBD_CMD_CACHE, will be a > useful way to prove that cache commands even make it through the > stack. (Remember, qemu 3.0 was released with a fatally flawed > NBD_CMD_CACHE server implementation, because there were no open source > clients at the time that could actually send the command to test the > server with). >

> > Unlike in other languages, you B<must> provide the C<can_*> methods > otherwise they are assumed to all return false and your C<pwrite>, > -C<flush>, C<trim>, C<zero> and C<extents> methods will never be > +C<flush>, C<trim>, C<zero>, and C<extents> methods will never be I wonder if you meant to add C<cache> to this sentence?