Re: [PATCH 3/6] tests/9pfs: compare QIDs in fs_walk_none() test

[Greg Kurz <groug@kaod.org>]

On Thu, 10 Mar 2022 10:04:50 +0100
Christian Schoenebeck <qemu_oss@crudebyte.com> wrote:

> On Mittwoch, 9. März 2022 15:49:04 CET Christian Schoenebeck wrote:
> > Extend previously added fs_walk_none() test by comparing the QID
> > of the root fid with the QID of the cloned fid. They should be
> > equal.
> > 

Ha, I understand your suggestion of changing the name now :-) but I'll
personally leave it named according to the test scenario of "sending
a Twalk with no names" and checking everything that is expected in this
case.

> > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
> > ---
> >  tests/qtest/virtio-9p-test.c | 70 ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 70 insertions(+)
> > 
> > diff --git a/tests/qtest/virtio-9p-test.c b/tests/qtest/virtio-9p-test.c
> > index 6c00da03f4..9098e21173 100644
> > --- a/tests/qtest/virtio-9p-test.c
> > +++ b/tests/qtest/virtio-9p-test.c
> > @@ -146,6 +146,11 @@ static void v9fs_uint16_read(P9Req *req, uint16_t *val)
> > le16_to_cpus(val);
> >  }
> > 
> > +static void v9fs_int16_read(P9Req *req, int16_t *val)
> > +{
> > +    v9fs_uint16_read(req, (uint16_t *)val);
> > +}
> > +
> >  static void v9fs_uint32_write(P9Req *req, uint32_t val)
> >  {
> >      uint32_t le_val = cpu_to_le32(val);
> > @@ -166,12 +171,22 @@ static void v9fs_uint32_read(P9Req *req, uint32_t
> > *val) le32_to_cpus(val);
> >  }
> > 
> > +static void v9fs_int32_read(P9Req *req, int32_t *val)
> > +{
> > +    v9fs_uint32_read(req, (uint32_t *)val);
> > +}
> > +
> >  static void v9fs_uint64_read(P9Req *req, uint64_t *val)
> >  {
> >      v9fs_memread(req, val, 8);
> >      le64_to_cpus(val);
> >  }
> > 
> > +static void v9fs_int64_read(P9Req *req, int64_t *val)
> > +{
> > +    v9fs_uint64_read(req, (uint64_t *)val);
> > +}
> > +
> >  /* len[2] string[len] */
> >  static uint16_t v9fs_string_size(const char *string)
> >  {
> > @@ -425,6 +440,40 @@ static void v9fs_rwalk(P9Req *req, uint16_t *nwqid,
> > v9fs_qid **wqid) v9fs_req_free(req);
> >  }
> > 
> > +/* size[4] Tstat tag[2] fid[4] */
> > +static P9Req *v9fs_tstat(QVirtio9P *v9p, uint32_t fid, uint16_t tag)

Tstat/Rstat aren't part of 9p2000.L, you should use Tgetattr/Rgetattr
instead (see https://github.com/chaos/diod/blob/master/protocol.md).

> > +{
> > +    P9Req *req;
> > +
> > +    req = v9fs_req_init(v9p, 4, P9_TSTAT, tag);
> > +    v9fs_uint32_write(req, fid);
> > +    v9fs_req_send(req);
> > +    return req;
> > +}
> > +
> > +/* size[4] Rstat tag[2] stat[n] */
> > +static void v9fs_rstat(P9Req *req, struct V9fsStat *st)
> > +{
> > +    v9fs_req_recv(req, P9_RSTAT);
> > +

For the records, this is a stat[n], i.e. "n[2] followed by n bytes of
data forming the parameter", so you should read an uint16_t first.

> > +    v9fs_int16_read(req, &st->size);
> > +    v9fs_int16_read(req, &st->type);
> > +    v9fs_int32_read(req, &st->dev);
> > +    v9fs_uint8_read(req, &st->qid.type);
> > +    v9fs_uint32_read(req, &st->qid.version);
> > +    v9fs_uint64_read(req, &st->qid.path);
> > +    v9fs_int32_read(req, &st->mode);
> > +    v9fs_int32_read(req, &st->mtime);
> > +    v9fs_int32_read(req, &st->atime);
> > +    v9fs_int64_read(req, &st->length);
> > +    v9fs_string_read(req, &st->name.size, &st->name.data);
> > +    v9fs_string_read(req, &st->uid.size, &st->uid.data);
> > +    v9fs_string_read(req, &st->gid.size, &st->gid.data);
> > +    v9fs_string_read(req, &st->muid.size, &st->muid.data);
> > +
> > +    v9fs_req_free(req);
> > +}
> > +
> >  /* size[4] Treaddir tag[2] fid[4] offset[8] count[4] */
> >  static P9Req *v9fs_treaddir(QVirtio9P *v9p, uint32_t fid, uint64_t offset,
> >                              uint32_t count, uint16_t tag)
> > @@ -1009,6 +1058,8 @@ static void fs_walk_none(void *obj, void *data,
> > QGuestAllocator *t_alloc) v9fs_qid root_qid;
> >      g_autofree v9fs_qid *wqid = NULL;
> >      P9Req *req;
> > +    struct V9fsStat st[2];
> > +    int i;
> > 
> >      do_version(v9p);
> >      req = v9fs_tattach(v9p, 0, getuid(), 0);
> > @@ -1021,6 +1072,25 @@ static void fs_walk_none(void *obj, void *data,
> > QGuestAllocator *t_alloc)
> > 
> >      /* special case: no QID is returned if nwname=0 was sent */
> >      g_assert(wqid == NULL);
> > +
> > +    req = v9fs_tstat(v9p, 0, 0);
> > +    v9fs_req_wait_for_reply(req, NULL);
> > +    v9fs_rstat(req, &st[0]);
> 
> Probably stat-ing the root fid (0) should happen before sending Twalk, to 
> better counter the 1st fid (0) having become potentially mutated?
> 

You already have the root qid from Rattach, no need to stat.

> > +
> > +    req = v9fs_tstat(v9p, 1, 0);
> > +    v9fs_req_wait_for_reply(req, NULL);
> > +    v9fs_rstat(req, &st[1]);
> > +
> > +    /* don't compare QID version for checking for file ID equalness */
> > +    g_assert(st[0].qid.type == st[1].qid.type);
> > +    g_assert(st[0].qid.path == st[1].qid.path);
> 
> I could add a helper function is_same_qid() for this if desired.
> 

Rgetattr provides a qid[13] like Rattach. Since we control everything,
the version bits won't change and I think is_same_qid() could be
something as simple as:

static inline bool is_same_qid(v9fs_qid qid1, v9fs_qid qid2)
{
    return memcmp(qid1, qid2, 13) == 0;
}

> > +
> > +    for (i = 0; i < 2; ++i) {
> > +        g_free(st[i].name.data);
> > +        g_free(st[i].uid.data);
> > +        g_free(st[i].gid.data);
> > +        g_free(st[i].muid.data);
> > +    }
> 
> I didn't find a more elegant way to do this cleanup.
> 

You won't need that with Tgetattr.
 
> >  }
> > 
> >  static void fs_walk_dotdot(void *obj, void *data, QGuestAllocator *t_alloc)
> 
>