[net/9p] Preparation and helper functions for zero copy

This patch prepares p9_fcall structure for zero copy. Added fields send the payload buffer information to the transport layer. In addition it adds a 'private' field for the transport layer to store mapped/pinned page information so that it can be freed/unpinned during req_done. This patch also creates trans_common.[ch] to house helper functions. It adds the following helper functions. p9_release_req_pages - Release pages after the transaction. p9_nr_pages - Return number of pages needed to accomodate the payload. payload_gup - Translates user buffer into kernel pages. Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

[net/9p] Preparation and helper functions for zero copy
This patch prepares p9_fcall structure for zero copy. Added fields send the payload buffer information to the transport layer. In addition it adds a 'private' field for the transport layer to store mapped/pinned page information so that it can be freed/unpinned during req_done. This patch also creates trans_common.[ch] to house helper functions. It adds the following helper functions. p9_release_req_pages - Release pages after the transaction. p9_nr_pages - Return number of pages needed to accomodate the payload. payload_gup - Translates user buffer into kernel pages. Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Venkateswararao Jujjuri (JV) · Eric Van Hensbergen
1 parent 6752a1ebd1
Showing 5 changed files with 139 additions and 0 deletions Side-by-side Diff
include/net/9p/9p.h
net/9p/Makefile
net/9p/protocol.c
net/9p/trans_common.c
net/9p/trans_common.h
@@ -689,6 +689,10 @@
  * @tag: transaction id of the request
  * @offset: used by marshalling routines to track currentposition in buffer
  * @capacity: used by marshalling routines to track total capacity
+ * @pubuf: Payload user buffer given by the caller
+ * @pubuf: Payload kernel buffer given by the caller
+ * @pbuf_size: pubuf/pkbuf(only one will be !NULL) size to be read/write.
+ * @private: For transport layer's use.
  * @sdata: payload
  *
  * &p9_fcall represents the structure for all 9P RPC
@@ -705,6 +709,10 @@
  
 	size_t offset;
 	size_t capacity;
+	char __user *pubuf;
+	char *pkbuf;
+	size_t pbuf_size;
+	void *private;
  
 	uint8_t *sdata;
 };
@@ -9,6 +9,7 @@
 	util.o \
 	protocol.o \
 	trans_fd.o \
+	trans_common.o \
  
 9pnet_virtio-objs := \
 	trans_virtio.o \
@@ -606,6 +606,10 @@
 {
 	pdu->offset = 0;
 	pdu->size = 0;
+	pdu->private = NULL;
+	pdu->pubuf = NULL;
+	pdu->pkbuf = NULL;
+	pdu->pbuf_size = 0;
 }
  
 int p9dirent_read(char *buf, int len, struct p9_dirent *dirent,
+/*
+ * Copyright IBM Corporation, 2010
+ * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <net/9p/9p.h>
+#include <net/9p/client.h>
+#include <linux/scatterlist.h>
+#include "trans_common.h"
+
+/**
+ *  p9_release_req_pages - Release pages after the transaction.
+ *  @*private: PDU's private page of struct trans_rpage_info
+ */
+void
+p9_release_req_pages(struct trans_rpage_info *rpinfo)
+{
+	int i = 0;
+
+	while (rpinfo->rp_data[i] && rpinfo->rp_nr_pages--) {
+		put_page(rpinfo->rp_data[i]);
+		i++;
+	}
+}
+EXPORT_SYMBOL(p9_release_req_pages);
+
+/**
+ * p9_nr_pages - Return number of pages needed to accomodate the payload.
+ */
+int
+p9_nr_pages(struct p9_req_t *req)
+{
+	int start_page, end_page;
+	start_page =  (unsigned long long)req->tc->pubuf >> PAGE_SHIFT;
+	end_page = ((unsigned long long)req->tc->pubuf + req->tc->pbuf_size +
+			PAGE_SIZE - 1) >> PAGE_SHIFT;
+	return end_page - start_page;
+}
+EXPORT_SYMBOL(p9_nr_pages);
+
+/**
+ * payload_gup - Translates user buffer into kernel pages and
+ * pins them either for read/write through get_user_pages_fast().
+ * @req: Request to be sent to server.
+ * @pdata_off: data offset into the first page after translation (gup).
+ * @pdata_len: Total length of the IO. gup may not return requested # of pages.
+ * @nr_pages: number of pages to accomodate the payload
+ * @rw: Indicates if the pages are for read or write.
+ */
+int
+p9_payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len,
+		int nr_pages, u8 rw)
+{
+	uint32_t first_page_bytes = 0;
+	uint32_t pdata_mapped_pages;
+	struct trans_rpage_info  *rpinfo;
+
+	*pdata_off = (size_t)req->tc->pubuf & (PAGE_SIZE-1);
+
+	if (*pdata_off)
+		first_page_bytes = min((PAGE_SIZE - *pdata_off),
+				req->tc->pbuf_size);
+
+	rpinfo = req->tc->private;
+	pdata_mapped_pages = get_user_pages_fast((unsigned long)req->tc->pubuf,
+			nr_pages, rw, &rpinfo->rp_data[0]);
+
+	if (pdata_mapped_pages < 0) {
+		printk(KERN_ERR "get_user_pages_fast failed:%d udata:%p"
+				"nr_pages:%d\n", pdata_mapped_pages,
+				req->tc->pubuf, nr_pages);
+		pdata_mapped_pages = 0;
+		return -EIO;
+	}
+	rpinfo->rp_nr_pages = pdata_mapped_pages;
+	if (*pdata_off) {
+		*pdata_len = first_page_bytes;
+		*pdata_len += min((req->tc->pbuf_size - *pdata_len),
+				((size_t)pdata_mapped_pages - 1) << PAGE_SHIFT);
+	} else {
+		*pdata_len = min(req->tc->pbuf_size,
+				(size_t)pdata_mapped_pages << PAGE_SHIFT);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(p9_payload_gup);
+/*
+ * Copyright IBM Corporation, 2010
+ * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ */
+
+/**
+ * struct trans_rpage_info - To store mapped page information in PDU.
+ * @rp_alloc:Set if this structure is allocd, not a reuse unused space in pdu.
+ * @rp_nr_pages: Number of mapped pages
+ * @rp_data: Array of page pointers
+ */
+struct trans_rpage_info {
+	u8 rp_alloc;
+	int rp_nr_pages;
+	struct page *rp_data[0];
+};
+
+void p9_release_req_pages(struct trans_rpage_info *);
+int p9_payload_gup(struct p9_req_t *, size_t *, int *, int, u8);
+int p9_nr_pages(struct p9_req_t *);
...	...	@@ -689,6 +689,10 @@
689	689	* @tag: transaction id of the request
690	690	* @offset: used by marshalling routines to track currentposition in buffer
691	691	* @capacity: used by marshalling routines to track total capacity
	692	+ * @pubuf: Payload user buffer given by the caller
	693	+ * @pubuf: Payload kernel buffer given by the caller
	694	+ * @pbuf_size: pubuf/pkbuf(only one will be !NULL) size to be read/write.
	695	+ * @private: For transport layer's use.
692	696	* @sdata: payload
693	697	*
694	698	* &p9_fcall represents the structure for all 9P RPC
...	...	@@ -705,6 +709,10 @@
705	709
706	710	size_t offset;
707	711	size_t capacity;
	712	+ char __user *pubuf;
	713	+ char *pkbuf;
	714	+ size_t pbuf_size;
	715	+ void *private;
708	716
709	717	uint8_t *sdata;
710	718	};
...	...	@@ -9,6 +9,7 @@
9	9	util.o \
10	10	protocol.o \
11	11	trans_fd.o \
	12	+ trans_common.o \
12	13
13	14	9pnet_virtio-objs := \
14	15	trans_virtio.o \
...	...	@@ -606,6 +606,10 @@
606	606	{
607	607	pdu->offset = 0;
608	608	pdu->size = 0;
	609	+ pdu->private = NULL;
	610	+ pdu->pubuf = NULL;
	611	+ pdu->pkbuf = NULL;
	612	+ pdu->pbuf_size = 0;
609	613	}
610	614
611	615	int p9dirent_read(char buf, int len, struct p9_dirent dirent,
	1	+/*
	2	+ * Copyright IBM Corporation, 2010
	3	+ * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
	4	+ *
	5	+ * This program is free software; you can redistribute it and/or modify it
	6	+ * under the terms of version 2.1 of the GNU Lesser General Public License
	7	+ * as published by the Free Software Foundation.
	8	+ *
	9	+ * This program is distributed in the hope that it would be useful, but
	10	+ * WITHOUT ANY WARRANTY; without even the implied warranty of
	11	+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
	12	+ *
	13	+ */
	14	+
	15	+#include <linux/slab.h>
	16	+#include <linux/module.h>
	17	+#include <net/9p/9p.h>
	18	+#include <net/9p/client.h>
	19	+#include <linux/scatterlist.h>
	20	+#include "trans_common.h"
	21	+
	22	+/**
	23	+ * p9_release_req_pages - Release pages after the transaction.
	24	+ * @*private: PDU's private page of struct trans_rpage_info
	25	+ */
	26	+void
	27	+p9_release_req_pages(struct trans_rpage_info *rpinfo)
	28	+{
	29	+ int i = 0;
	30	+
	31	+ while (rpinfo->rp_data[i] && rpinfo->rp_nr_pages--) {
	32	+ put_page(rpinfo->rp_data[i]);
	33	+ i++;
	34	+ }
	35	+}
	36	+EXPORT_SYMBOL(p9_release_req_pages);
	37	+
	38	+/**
	39	+ * p9_nr_pages - Return number of pages needed to accomodate the payload.
	40	+ */
	41	+int
	42	+p9_nr_pages(struct p9_req_t *req)
	43	+{
	44	+ int start_page, end_page;
	45	+ start_page = (unsigned long long)req->tc->pubuf >> PAGE_SHIFT;
	46	+ end_page = ((unsigned long long)req->tc->pubuf + req->tc->pbuf_size +
	47	+ PAGE_SIZE - 1) >> PAGE_SHIFT;
	48	+ return end_page - start_page;
	49	+}
	50	+EXPORT_SYMBOL(p9_nr_pages);
	51	+
	52	+/**
	53	+ * payload_gup - Translates user buffer into kernel pages and
	54	+ * pins them either for read/write through get_user_pages_fast().
	55	+ * @req: Request to be sent to server.
	56	+ * @pdata_off: data offset into the first page after translation (gup).
	57	+ * @pdata_len: Total length of the IO. gup may not return requested # of pages.
	58	+ * @nr_pages: number of pages to accomodate the payload
	59	+ * @rw: Indicates if the pages are for read or write.
	60	+ */
	61	+int
	62	+p9_payload_gup(struct p9_req_t req, size_t pdata_off, int *pdata_len,
	63	+ int nr_pages, u8 rw)
	64	+{
	65	+ uint32_t first_page_bytes = 0;
	66	+ uint32_t pdata_mapped_pages;
	67	+ struct trans_rpage_info *rpinfo;
	68	+
	69	+ *pdata_off = (size_t)req->tc->pubuf & (PAGE_SIZE-1);
	70	+
	71	+ if (*pdata_off)
	72	+ first_page_bytes = min((PAGE_SIZE - *pdata_off),
	73	+ req->tc->pbuf_size);
	74	+
	75	+ rpinfo = req->tc->private;
	76	+ pdata_mapped_pages = get_user_pages_fast((unsigned long)req->tc->pubuf,
	77	+ nr_pages, rw, &rpinfo->rp_data[0]);
	78	+
	79	+ if (pdata_mapped_pages < 0) {
	80	+ printk(KERN_ERR "get_user_pages_fast failed:%d udata:%p"
	81	+ "nr_pages:%d\n", pdata_mapped_pages,
	82	+ req->tc->pubuf, nr_pages);
	83	+ pdata_mapped_pages = 0;
	84	+ return -EIO;
	85	+ }
	86	+ rpinfo->rp_nr_pages = pdata_mapped_pages;
	87	+ if (*pdata_off) {
	88	+ *pdata_len = first_page_bytes;
	89	+ pdata_len += min((req->tc->pbuf_size - pdata_len),
	90	+ ((size_t)pdata_mapped_pages - 1) << PAGE_SHIFT);
	91	+ } else {
	92	+ *pdata_len = min(req->tc->pbuf_size,
	93	+ (size_t)pdata_mapped_pages << PAGE_SHIFT);
	94	+ }
	95	+ return 0;
	96	+}
	97	+EXPORT_SYMBOL(p9_payload_gup);