Re: [Libguestfs] [nbdkit PATCH 2/4] nbd: Normalize return values of can_*

On 3/17/20 3:12 AM, Richard W.M. Jones wrote: >On Mon, Mar 16, 2020 at 10:36:15PM -0500, Eric Blake wrote: >>Although nbdkit documents that any positive value should be treated as >>success to the .can_* callbacks, we had a window of releases where >>anything other than 1 could trigger an assertion failure, fixed in the >>previous patch. Update what we return to avoid tripping the bug in >>broken nbdkit. >> >>Our return value has been latent since 0e8e8eb11d (v1.1.17), but the >>assertion failures did not occur until c306fa93ab and neighboring >>commits (v1.15.1). As v1.13.6 was the point where we started >>preferring builds against libnbd, where we always returned 1 on >>success, the problem was not detected until now; but it is still in >>the wild for any user mixing old plugins with new libnbd. >> >>Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; >>--- >> plugins/nbd/nbd-standalone.c | 12 ++++++------ >> 1 file changed, 6 insertions(+), 6 deletions(-) >While I don't like the idea of modifying plugins to fix broken nbdkit >behaviour, you make a good case for this being safer, so: > >ACK Think of it as working around broken nbdkit behavior, rather than fixing it (as the fix is in patch 1/4). How many stable branches should we backport this to? Going all the way back to stable-1.2 seems like it might be overkill; maybe back to stable-1.14 (where nbd-standalone was first split off) or stable-1.12 (the last release that did not use libnbd) is sufficient?