Re: [PATCH v4 4/9] virtiofsd: Extend size of fuse_conn_info->capable and ->want fields

[Vivek Goyal <vgoyal@redhat.com>]

On Thu, Jan 27, 2022 at 05:53:20PM +0000, Dr. David Alan Gilbert wrote:
> * Vivek Goyal (vgoyal@redhat.com) wrote:
> > ->capable keeps track of what capabilities kernel supports and ->wants keep
> > track of what capabilities filesytem wants.
> > 
> > Right now these fields are 32bit in size. But now fuse has run out of
> > bits and capabilities can now have bit number which are higher than 31.
> > 
> > That means 32 bit fields are not suffcient anymore. Increase size to 64
> > bit so that we can add newer capabilities and still be able to use existing
> > code to check and set the capabilities.
> > 
> > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> > ---
> >  tools/virtiofsd/fuse_common.h   | 4 ++--
> >  tools/virtiofsd/fuse_lowlevel.c | 2 +-
> >  2 files changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/virtiofsd/fuse_common.h b/tools/virtiofsd/fuse_common.h
> > index 0c2665b977..6f8a988202 100644
> > --- a/tools/virtiofsd/fuse_common.h
> > +++ b/tools/virtiofsd/fuse_common.h
> > @@ -439,7 +439,7 @@ struct fuse_conn_info {
> >      /**
> >       * Capability flags that the kernel supports (read-only)
> >       */
> > -    unsigned capable;
> > +    uint64_t capable;
> >  
> >      /**
> >       * Capability flags that the filesystem wants to enable.
> > @@ -447,7 +447,7 @@ struct fuse_conn_info {
> >       * libfuse attempts to initialize this field with
> >       * reasonable default values before calling the init() handler.
> >       */
> > -    unsigned want;
> > +    uint64_t want;
> >  
> >      /**
> >       * Maximum number of pending "background" requests. A
> > diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c
> > index c3af5ede08..f3f5e70be6 100644
> > --- a/tools/virtiofsd/fuse_lowlevel.c
> > +++ b/tools/virtiofsd/fuse_lowlevel.c
> > @@ -2063,7 +2063,7 @@ static void do_init(fuse_req_t req, fuse_ino_t nodeid,
> >      if (se->conn.want & (~se->conn.capable)) {
> >          fuse_log(FUSE_LOG_ERR,
> >                   "fuse: error: filesystem requested capabilities "
> > -                 "0x%x that are not supported by kernel, aborting.\n",
> > +                 "0x%lx that are not supported by kernel, aborting.\n",
> 
> I think this will be OK in practice (need to check 32 bit); but weren't
> you using llx in the last patch?

Probably I should use %llx so that it works fine on 32 bit. Will change
it.

Vivek

> 
> 
> 
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 
> Dave
> 
> >                   se->conn.want & (~se->conn.capable));
> >          fuse_reply_err(req, EPROTO);
> >          se->error = -EPROTO;
> > -- 
> > 2.31.1
> > 
> -- 
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>