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Message-ID: <874o1j0za9.fsf@skywalker.in.ibm.com>
Date: Mon, 15 Aug 2011 15:31:02 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: mohan@...p.linux.ibm.com
Cc: v9fs-developer@...ts.sourceforge.net,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [V9fs-developer] [PATCH] fs/9p: Update zero-copy implementation in 9p
On Mon, 15 Aug 2011 05:27:42 -0400, mohan@...p.linux.ibm.com wrote:
>
> [snip]
>
> > + * p9_client_zc_rpc - issue a request and wait for a response
> > + * @c: client session
> > + * @type: type of request
> > + * @uidata: user bffer that should be ued for zero copy read
> > + * @uodata: user buffer that shoud be user for zero copy write
> > + * @inlen: read buffer size
> > + * @olen: write buffer size
> > + * @hdrlen: reader header size, This is the size of response protocol data
> > + * @fmt: protocol format string (see protocol.c)
> > + *
> > + * Returns request structure (which client must free using p9_free_req)
> > + */
> > +static struct p9_req_t *p9_client_zc_rpc(struct p9_client *c, int8_t type,
> > + char *uidata, char *uodata,
> > + int inlen, int olen, int in_hdrlen,
> > + int kern_buf, const char *fmt, ...)
>
> Most of the code is duplicated from p9_client_rpc, is it possible to write a
> helper routine which can be used by both p9_client_rpc &
> p9_client_zc_rpc?
I will try that.
> > +{
> > + va_list ap;
> > + int tag, err;
> > + struct p9_req_t *req;
> > + unsigned long flags;
> > + int sigpending;
> > +
> > + P9_DPRINTK(P9_DEBUG_MUX, "client %p op %d\n", c, type);
> > +
> > + /* we allow for any status other than disconnected */
> > + if (c->status == Disconnected)
> > + return ERR_PTR(-EIO);
> > +
> > + /* If we are called with KERNEL_DS force kern_buf */
> > + if (segment_eq(get_fs(), KERNEL_DS))
> > + kern_buf = 1;
> > +
> > + /* if status is begin_disconnected we allow only clunk request */
> > + if ((c->status == BeginDisconnect) && (type != P9_TCLUNK))
> > + return ERR_PTR(-EIO);
> > +
> > + if (signal_pending(current)) {
> > + sigpending = 1;
> > + clear_thread_flag(TIF_SIGPENDING);
> > + } else
> > + sigpending = 0;
> > +
> > + tag = P9_NOTAG;
> > + if (type != P9_TVERSION) {
> > + tag = p9_idpool_get(c->tagpool);
> > + if (tag < 0)
> > + return ERR_PTR(-ENOMEM);
> > + }
> > + /*
> > + * We allocate a inline protocol data of only 4k bytes.
> > + * The actual content is passed in zero-copy fashion.
> > + */
> > + req = p9_tag_alloc(c, tag, P9_ZC_HDR_SZ);
> > + if (IS_ERR(req))
> > + return req;
> > +
> > + /* marshall the data */
> > + p9pdu_prepare(req->tc, tag, type);
> > + va_start(ap, fmt);
> > + err = p9pdu_vwritef(req->tc, c->proto_version, fmt, ap);
> > + va_end(ap);
> > + if (err)
> > + goto reterr;
> > + p9pdu_finalize(req->tc);
> > +
> > + err = c->trans_mod->zc_request(c, req, uidata, uodata,
> > + inlen, olen, in_hdrlen, kern_buf);
> > + if (err < 0) {
> > + if (err == -EIO)
> > + c->status = Disconnected;
> > + goto reterr;
> > + }
> > + if (req->status == REQ_STATUS_ERROR) {
> > + P9_DPRINTK(P9_DEBUG_ERROR, "req_status error %d\n", req->t_err);
> > + err = req->t_err;
> > + }
> > + if ((err == -ERESTARTSYS) && (c->status == Connected)) {
> > + P9_DPRINTK(P9_DEBUG_MUX, "flushing\n");
> > + sigpending = 1;
> > + clear_thread_flag(TIF_SIGPENDING);
> > +
> > + if (c->trans_mod->cancel(c, req))
> > + p9_client_flush(c, req);
> > +
> > + /* if we received the response anyway, don't signal error */
> > + if (req->status == REQ_STATUS_RCVD)
> > + err = 0;
> > + }
> > + if (sigpending) {
> > + spin_lock_irqsave(¤t->sighand->siglock, flags);
> > + recalc_sigpending();
> > + spin_unlock_irqrestore(¤t->sighand->siglock, flags);
> > + }
> > + if (err < 0)
> > + goto reterr;
> > +
> > + err = p9_check_zc_errors(c, req, uidata, in_hdrlen, kern_buf);
> > + if (!err) {
> > + P9_DPRINTK(P9_DEBUG_MUX, "exit: client %p op %d\n", c, type);
> > + return req;
> > + }
> > +reterr:
> > + P9_DPRINTK(P9_DEBUG_MUX, "exit: client %p op %d error: %d\n", c, type,
> > + err);
> > + p9_free_req(c, req);
> > + return ERR_PTR(err);
> > +}
> > +
> > static struct p9_fid *p9_fid_create(struct p9_client *clnt)
> > {
> > int ret;
> > @@ -1329,13 +1512,15 @@ int
> > p9_client_read(struct p9_fid *fid, char *data, char __user *udata,
> > u64 offset,
> > u32 count)
> > {
> > - int err, rsize;
> > - struct p9_client *clnt;
> > - struct p9_req_t *req;
> > char *dataptr;
> > + int kernel_buf = 0;
> > + struct p9_req_t *req;
> > + struct p9_client *clnt;
> > + int err, rsize, non_zc = 0;
> > +
> >
> > - P9_DPRINTK(P9_DEBUG_9P, ">>> TREAD fid %d offset %llu %d\n", fid->fid,
> > - (long long unsigned) offset, count);
> > + P9_DPRINTK(P9_DEBUG_9P, ">>> TREAD fid %d offset %llu %d\n",
> > + fid->fid, (long long unsigned) offset, count);
> > err = 0;
> > clnt = fid->clnt;
> >
> > @@ -1346,14 +1531,25 @@ p9_client_read(struct p9_fid *fid, char
> > *data, char __user *udata, u64 offset,
> > if (count < rsize)
> > rsize = count;
> >
> > - /* Don't bother zerocopy for small IO (< 1024) */
> > - if (((clnt->trans_mod->pref & P9_TRANS_PREF_PAYLOAD_MASK) ==
> > - P9_TRANS_PREF_PAYLOAD_SEP) && (rsize > 1024)) {
> > - req = p9_client_rpc(clnt, P9_TREAD, "dqE", fid->fid, offset,
> > - rsize, data, udata);
> > + /* Don't bother zerocopy form small IO (< 1024) */
> form Typo?
Yes. Will fix in next update.
> > + if (clnt->trans_mod->zc_request && rsize > 1024) {
> > + char *indata;
> > + if (data) {
> > + kernel_buf = 1;
> > + indata = data;
> > + } else
> > + indata = (char *)udata;
> > + /*
> > + * response header len is 11
> > + * PDU Header(7) + IO Size (4)
> > + */
> > + req = p9_client_zc_rpc(clnt, P9_TREAD, indata, NULL, rsize, 0,
> > + 11, kernel_buf, "dqd", fid->fid,
> > + offset, rsize);
>
-aneesh
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