cifs: teach smb_send_rqst how to handle arrays of pages

Add code that allows smb_send_rqst to send an array of pages after the initial kvec array has been sent. For now, we simply kmap the page array and send it using the standard smb_send_kvec function. Eventually, we may want to convert this code to use kernel_sendpage under the hood and avoid the kmap altogether for the page data. Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <smfrench@gmail.com>

cifs: teach smb_send_rqst how to handle arrays of pages
Add code that allows smb_send_rqst to send an array of pages after the initial kvec array has been sent. For now, we simply kmap the page array and send it using the standard smb_send_kvec function. Eventually, we may want to convert this code to use kernel_sendpage under the hood and avoid the kmap altogether for the page data. Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <smfrench@gmail.com>
Jeff Layton · Steve French
1 parent b8eed28375
Showing 1 changed file with 54 additions and 2 deletions Side-by-side Diff
fs/cifs/transport.c
@@ -28,6 +28,7 @@
 #include <linux/delay.h>
 #include <linux/freezer.h>
 #include <linux/tcp.h>
+#include <linux/highmem.h>
 #include <asm/uaccess.h>
 #include <asm/processor.h>
 #include <linux/mempool.h>
@@ -240,6 +241,38 @@
 	return rc;
 }
  
+/**
+ * rqst_page_to_kvec - Turn a slot in the smb_rqst page array into a kvec
+ * @rqst: pointer to smb_rqst
+ * @idx: index into the array of the page
+ * @iov: pointer to struct kvec that will hold the result
+ *
+ * Helper function to convert a slot in the rqst->rq_pages array into a kvec.
+ * The page will be kmapped and the address placed into iov_base. The length
+ * will then be adjusted according to the ptailoff.
+ */
+static void
+cifs_rqst_page_to_kvec(struct smb_rqst *rqst, unsigned int idx,
+			struct kvec *iov)
+{
+	/*
+	 * FIXME: We could avoid this kmap altogether if we used
+	 * kernel_sendpage instead of kernel_sendmsg. That will only
+	 * work if signing is disabled though as sendpage inlines the
+	 * page directly into the fraglist. If userspace modifies the
+	 * page after we calculate the signature, then the server will
+	 * reject it and may break the connection. kernel_sendmsg does
+	 * an extra copy of the data and avoids that issue.
+	 */
+	iov->iov_base = kmap(rqst->rq_pages[idx]);
+
+	/* if last page, don't send beyond this offset into page */
+	if (idx == (rqst->rq_npages - 1))
+		iov->iov_len = rqst->rq_tailsz;
+	else
+		iov->iov_len = rqst->rq_pagesz;
+}
+
 static int
 smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
 {
@@ -247,7 +280,8 @@
 	struct kvec *iov = rqst->rq_iov;
 	int n_vec = rqst->rq_nvec;
 	unsigned int smb_buf_length = get_rfc1002_length(iov[0].iov_base);
-	size_t total_len;
+	unsigned int i;
+	size_t total_len = 0, sent;
 	struct socket *ssocket = server->ssocket;
 	int val = 1;
  
  
@@ -258,8 +292,26 @@
 	kernel_setsockopt(ssocket, SOL_TCP, TCP_CORK,
 				(char *)&val, sizeof(val));
  
-	rc = smb_send_kvec(server, iov, n_vec, &total_len);
+	rc = smb_send_kvec(server, iov, n_vec, &sent);
+	if (rc < 0)
+		goto uncork;
  
+	total_len += sent;
+
+	/* now walk the page array and send each page in it */
+	for (i = 0; i < rqst->rq_npages; i++) {
+		struct kvec p_iov;
+
+		cifs_rqst_page_to_kvec(rqst, i, &p_iov);
+		rc = smb_send_kvec(server, &p_iov, 1, &sent);
+		kunmap(rqst->rq_pages[i]);
+		if (rc < 0)
+			break;
+
+		total_len += sent;
+	}
+
+uncork:
 	/* uncork it */
 	val = 0;
 	kernel_setsockopt(ssocket, SOL_TCP, TCP_CORK,
...	...	@@ -28,6 +28,7 @@
28	28	#include <linux/delay.h>
29	29	#include <linux/freezer.h>
30	30	#include <linux/tcp.h>
	31	+#include <linux/highmem.h>
31	32	#include <asm/uaccess.h>
32	33	#include <asm/processor.h>
33	34	#include <linux/mempool.h>
...	...	@@ -240,6 +241,38 @@
240	241	return rc;
241	242	}
242	243
	244	+/**
	245	+ * rqst_page_to_kvec - Turn a slot in the smb_rqst page array into a kvec
	246	+ * @rqst: pointer to smb_rqst
	247	+ * @idx: index into the array of the page
	248	+ * @iov: pointer to struct kvec that will hold the result
	249	+ *
	250	+ * Helper function to convert a slot in the rqst->rq_pages array into a kvec.
	251	+ * The page will be kmapped and the address placed into iov_base. The length
	252	+ * will then be adjusted according to the ptailoff.
	253	+ */
	254	+static void
	255	+cifs_rqst_page_to_kvec(struct smb_rqst *rqst, unsigned int idx,
	256	+ struct kvec *iov)
	257	+{
	258	+ /*
	259	+ * FIXME: We could avoid this kmap altogether if we used
	260	+ * kernel_sendpage instead of kernel_sendmsg. That will only
	261	+ * work if signing is disabled though as sendpage inlines the
	262	+ * page directly into the fraglist. If userspace modifies the
	263	+ * page after we calculate the signature, then the server will
	264	+ * reject it and may break the connection. kernel_sendmsg does
	265	+ * an extra copy of the data and avoids that issue.
	266	+ */
	267	+ iov->iov_base = kmap(rqst->rq_pages[idx]);
	268	+
	269	+ /* if last page, don't send beyond this offset into page */
	270	+ if (idx == (rqst->rq_npages - 1))
	271	+ iov->iov_len = rqst->rq_tailsz;
	272	+ else
	273	+ iov->iov_len = rqst->rq_pagesz;
	274	+}
	275	+
243	276	static int
244	277	smb_send_rqst(struct TCP_Server_Info server, struct smb_rqst rqst)
245	278	{
...	...	@@ -247,7 +280,8 @@
247	280	struct kvec *iov = rqst->rq_iov;
248	281	int n_vec = rqst->rq_nvec;
249	282	unsigned int smb_buf_length = get_rfc1002_length(iov[0].iov_base);
250		- size_t total_len;
	283	+ unsigned int i;
	284	+ size_t total_len = 0, sent;
251	285	struct socket *ssocket = server->ssocket;
252	286	int val = 1;
253	287
254	288
...	...	@@ -258,8 +292,26 @@
258	292	kernel_setsockopt(ssocket, SOL_TCP, TCP_CORK,
259	293	(char *)&val, sizeof(val));
260	294
261		- rc = smb_send_kvec(server, iov, n_vec, &total_len);
	295	+ rc = smb_send_kvec(server, iov, n_vec, &sent);
	296	+ if (rc < 0)
	297	+ goto uncork;
262	298
	299	+ total_len += sent;
	300	+
	301	+ /* now walk the page array and send each page in it */
	302	+ for (i = 0; i < rqst->rq_npages; i++) {
	303	+ struct kvec p_iov;
	304	+
	305	+ cifs_rqst_page_to_kvec(rqst, i, &p_iov);
	306	+ rc = smb_send_kvec(server, &p_iov, 1, &sent);
	307	+ kunmap(rqst->rq_pages[i]);
	308	+ if (rc < 0)
	309	+ break;
	310	+
	311	+ total_len += sent;
	312	+ }
	313	+
	314	+uncork:
263	315	/* uncork it */
264	316	val = 0;
265	317	kernel_setsockopt(ssocket, SOL_TCP, TCP_CORK,