Re: [Qemu-devel] [PATCH v2 1/7] block/ssh: don't call libssh2_init() in block_init()

[Jeff Cody <jcody@redhat.com>]

On Wed, Aug 30, 2017 at 02:40:16PM -0500, Eric Blake wrote:
> On 08/30/2017 11:56 AM, Jeff Cody wrote:
> > We don't need libssh2 failure to be fatal (we could just opt to not
> > register the driver on failure). But, it is probably a good idea to
> > avoid external library calls during the block_init(), and call the
> > libssh2 global init function on the first usage, returning any errors.
> > 
> > Signed-off-by: Jeff Cody <jcody@redhat.com>
> > ---
> >  block/ssh.c | 40 +++++++++++++++++++++++++++++-----------
> >  1 file changed, 29 insertions(+), 11 deletions(-)
> > 
> 
> > +static int ssh_state_init(BDRVSSHState *s, Error **errp)
> >  {
> > +    int ret;
> > +
> > +    if (!ssh_libinit_called) {
> > +        ret = libssh2_init(0);
> > +        if (ret) {
> > +            error_setg(errp, "libssh2 initialization failed with %d", ret);
> > +            return ret;
> 
> Do we know if this number is always positive or negative?
> 

>From the documentation [1], it returns 0 on success, or a negative value
for error.  (I guess presumably that means a positive value is by definition
an error, as well).

[1] https://www.libssh2.org/libssh2_init.html

> > @@ -772,8 +788,13 @@ static int ssh_file_open(BlockDriverState *bs, QDict *options, int bdrv_flags,
> >      BDRVSSHState *s = bs->opaque;
> >      int ret;
> >      int ssh_flags;
> > +    Error *local_err = NULL;
> >  
> > -    ssh_state_init(s);
> > +    ret = ssh_state_init(s, &local_err);
> > +    if (local_err) {
> > +        error_propagate(errp, local_err);
> > +        return ret;
> 
> Is returning 'ret' from libssh2_init() wise?
> 
> If 'ret' is not important, you could simplify this:
> 
> if (ssh_state_init(s, errp)) {
>     return -1;
> }

Good point, not sure if a non-zero ret from libssh2_init() provides meaning
beyond 'error' for us.  Maybe return -EIO instead of -1, though?