On Thu, Jun 07, 2018 at 03:20:24PM +0200, Markus Armbruster wrote: > Daniel P. Berrangé <berra...@redhat.com> writes: > > > On Fri, Jun 01, 2018 at 05:18:35PM +0800, Fam Zheng wrote: > >> When hot-plugging a block device fails due to image locking errors, > >> users won't see the helpful 'Is another process using the image?' > >> message in QMP because currently the error hint is not carried over > >> there. > >> > >> Even though extending QMP to include hint is a conceivably easy task, > >> Libvirt will need some change to consume that data. > >> > >> Before that is fully sorted out, let's just do the easy fix by joining > >> the two lines. > > > > There are many places in QEMU which uses error hints and these are all > > invisible to libvirt. Arbitrarily picking one hint to remove, while > > leaving everything else unfixed is not a very satisfactory approach. > > > > If QEMU passes the hint in QMP, it is trivial for libvirt to be changed > > to append the hint when reporting its own error message, so can we just > > focus on fixing the root cause instead of special casing file-posix.c > > Intended use of hints according to error.h: > > * Intended use is adding helpful hints on the human user interface, > * e.g. a list of valid values. It's not for clarifying a confusing > * error message. > > I admit this guidance is widely ignored.
Perhaps if we rename the function "error_append_hmp_hint" it would make it obvious this is targetted at CLI users, and not QMP users, and so encourage people to write better initial messages ? > > When used as intended, the hints need not make any sense in QMP! > Consider this example in qemu-option.c: > > error_setg(errp, QERR_INVALID_PARAMETER_VALUE, name, > "a non-negative number below 2^64"); > error_append_hint(errp, "Optional suffix k, M, G, T, P or E means" > " kilo-, mega-, giga-, tera-, peta-\n" > "and exabytes, respectively.\n"); > > The suffixes are only available in the human interface. > > Aside: we have lots of code consuming input from both QMP and HMP / CLI. > The error reporting is generally atrocious for at least one of the two. > > Perhaps we could use separate functions for providing syntax hints and > for clarifying confusing error messages. Patches welcome, but they > better convert all existing uses. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
