I take back the question, because I just found that for a succeed
write opetion in the class, *no* data in the out buffer...
On Wed, Feb 4, 2015 at 5:44 PM, Dennis Chen <kernel.org....@gmail.com> wrote:
> Hello,
>
> I write a ceph client using rados lib to execute a funcution upon the object.
>
> CLIENT SIDE CODE
> ===============
> int main()
> {
> ...
> strcpy(in, "from client");
> err = rados_exec(io, objname, "devctl", "devctl_op", in,
> strlen(in), out, 128);
> if (err < 0) {
> fprintf(stderr, "rados_exec() failed: %s\n", strerror(-err));
> rados_ioctx_destroy(io);
> rados_shutdown(cluster);
> exit(1);
> }
> out[err] = '\0';
> printf("err = %d, exec result out = %s, in = %s\n", err, out, in);
> ...
> }
>
> CLASS CODE IN OSD SIDE
> ======================
> static int devctl_op(cls_method_context_t hctx, bufferlist *in, bufferlist
> *out)
> {
> ...
>
> i = cls_cxx_stat(hctx, &size, NULL);
> if (i < 0)
> return i;
>
> bufferlist read_bl, write_bl;
> i = cls_cxx_read(hctx, 0, size, &read_bl);
> if (i < 0) {
> CLS_ERR("cls_cxx_read failed");
> return i;
> }
>
>
> // we generate our reply
> out->append("Hello, ");
> if (in->length() == 0)
> out->append("world");
> else
> out->append(*in);
> out->append("!");
>
> #if 1
> const char *tstr = "from devctl func";
> write_bl.append(tstr);
> i = cls_cxx_write(hctx, size, write_bl.length(), &write_bl);
> if (i < 0) {
> CLS_ERR("cls_cxx_write failed: %s", strerror(-i));
> return i;
> }
> #endif
>
> // this return value will be returned back to the librados caller
> return 0;
> }
>
> I found that if I update the content of the object when calling
> cls_cxx_write(), then the 'out' will be null in the client side,
> otherwise the out will be "Hello, from client!".
>
> Does anybody here can give some hints?
>
> --
> Den
--
Den
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