CIFS: Use multicredits for SMB 2.1/3 reads

If we negotiate SMB 2.1 and higher version of the protocol and
a server supports large read buffer size, we need to consume 1
credit per 65536 bytes. So, we need to know how many credits
we have and obtain the required number of them before constructing
a readdata structure in readpages and user read.

Reviewed-by: Shirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 27 insertions, 3 deletions

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index be7b2eb..c31e5a0 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1747,11 +1747,12 @@ smb2_readv_callback(struct mid_q_entry *mid)
 int
 smb2_async_readv(struct cifs_readdata *rdata)
 {
-	int rc;
+	int rc, flags = 0;
 	struct smb2_hdr *buf;
 	struct cifs_io_parms io_parms;
 	struct smb_rqst rqst = { .rq_iov = &rdata->iov,
 				 .rq_nvec = 1 };
+	struct TCP_Server_Info *server;
 
 	cifs_dbg(FYI, "%s: offset=%llu bytes=%u\n",
 		 __func__, rdata->offset, rdata->bytes);
@@ -1762,18 +1763,41 @@ smb2_async_readv(struct cifs_readdata *rdata)
 	io_parms.persistent_fid = rdata->cfile->fid.persistent_fid;
 	io_parms.volatile_fid = rdata->cfile->fid.volatile_fid;
 	io_parms.pid = rdata->pid;
+
+	server = io_parms.tcon->ses->server;
+
 	rc = smb2_new_read_req(&rdata->iov, &io_parms, 0, 0);
-	if (rc)
+	if (rc) {
+		if (rc == -EAGAIN && rdata->credits) {
+			/* credits was reset by reconnect */
+			rdata->credits = 0;
+			/* reduce in_flight value since we won't send the req */
+			spin_lock(&server->req_lock);
+			server->in_flight--;
+			spin_unlock(&server->req_lock);
+		}
 		return rc;
+	}
 
 	buf = (struct smb2_hdr *)rdata->iov.iov_base;
 	/* 4 for rfc1002 length field */
 	rdata->iov.iov_len = get_rfc1002_length(rdata->iov.iov_base) + 4;
 
+	if (rdata->credits) {
+		buf->CreditCharge = cpu_to_le16(DIV_ROUND_UP(rdata->bytes,
+						SMB2_MAX_BUFFER_SIZE));
+		spin_lock(&server->req_lock);
+		server->credits += rdata->credits -
+						le16_to_cpu(buf->CreditCharge);
+		spin_unlock(&server->req_lock);
+		wake_up(&server->request_q);
+		flags = CIFS_HAS_CREDITS;
+	}
+
 	kref_get(&rdata->refcount);
 	rc = cifs_call_async(io_parms.tcon->ses->server, &rqst,
 			     cifs_readv_receive, smb2_readv_callback,
-			     rdata, 0);
+			     rdata, flags);
 	if (rc) {
 		kref_put(&rdata->refcount, cifs_readdata_release);
 		cifs_stats_fail_inc(io_parms.tcon, SMB2_READ_HE);