On Fri, May 17, 2019 at 04:05:22PM -0500, Eric Blake wrote: > It is possible for the round-up parameter to cause our desired size to > exceed 2**63-1. But this error message is cryptic: > > $ ./nbdkit -f --filter=truncate pattern $(((1<<63)-1)) round-up=1m & > $ qemu-nbd --list > nbdkit: pattern[1]: error: .get_size function returned invalid value > (-9223372036854775808) > qemu-nbd: Failed to read initial magic: Unexpected end-of-file before all > bytes were read > > Better is the result of this patch: > nbdkit: pattern[1]: error: cannot round size 9223372036854775807 up to next > boundary of 1048576 > > Alas, we are still limited in the fact that we can only detect the > problem on a per-connection basis (at .prepare, rather than at .load) > (because we support plugins that have a different size per > connection); and that nbdkit in general is still rather rude to > clients when .prepare prevents the use of a connection (perhaps nbdkit > should instead be taught to proceed with the socekt, but respond to > NBD_OPT_LIST with 0 items and to NBD_OPT_GO with NBD_REP_ERR_UNKNOWN > or NBD_REP_ERR_SHUTDOWN to give the client a hint that this server has > nothing further to offer). > > Signed-off-by: Eric Blake <[email protected]> > --- > > I pushed this one, but am posting to the list because of the > conversation points it brings up about what to do when .prepare fails > (there's a difference between refusing to start nbdkit because .config > failed, vs. starting but being useless to a client because > .open/.prepare failed). > > filters/truncate/truncate.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/filters/truncate/truncate.c b/filters/truncate/truncate.c > index 6408c35..bed5a03 100644 > --- a/filters/truncate/truncate.c > +++ b/filters/truncate/truncate.c > @@ -38,6 +38,7 @@ > #include <string.h> > #include <limits.h> > #include <errno.h> > +#include <inttypes.h> > > #include <nbdkit-filter.h> > > @@ -172,8 +173,14 @@ truncate_prepare (struct nbdkit_next_ops *next_ops, void > *nxdata, > */ > if (truncate_size >= 0) > h->size = truncate_size; > - if (round_up > 0) > + if (round_up > 0) { > + if (ROUND_UP (h->size, round_up) > INT64_MAX) { > + nbdkit_error ("cannot round size %" PRId64 " up to next boundary of > %u", > + h->size, round_up); > + return -1; > + } > h->size = ROUND_UP (h->size, round_up); > + } > if (round_down > 0) > h->size = ROUND_DOWN (h->size, round_down); > > -- > 2.20.1
Looks sensible anyway, thanks for pushing it. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into KVM guests. http://libguestfs.org/virt-v2v _______________________________________________ Libguestfs mailing list [email protected] https://www.redhat.com/mailman/listinfo/libguestfs
