This patch avoids copy_to_user by employing get_user_pages_fast() on the
udata buffer. This will eliminate an additonal copy of kernel buffer into
user buffer. We filter out the kernel buffers (kernel_read()) by comparing
segments.
Signed-off-by: Venkateswararao Jujjuri <jvrao@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Badari Pulavarty <pbadari@xxxxxxxxxx>
---
net/9p/client.c | 18 ++++++++++++++++--
net/9p/protocol.c | 33 +++++++++++++++++++++++++++++++--
2 files changed, 47 insertions(+), 4 deletions(-)
diff --git a/net/9p/client.c b/net/9p/client.c
index 7ce58fb..d11c7dd 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1282,6 +1282,7 @@ p9_client_read(struct p9_fid *fid, char *data, char __user *udata, u64 offset,
struct p9_client *clnt;
struct p9_req_t *req;
char *dataptr;
+ int page_direct = 0;
P9_DPRINTK(P9_DEBUG_9P, ">>> TREAD fid %d offset %llu %d\n", fid->fid,
(long long unsigned) offset, count);
@@ -1296,7 +1297,20 @@ p9_client_read(struct p9_fid *fid, char *data, char __user *udata, u64 offset,
if (count < rsize)
rsize = count;
- req = p9_client_rpc(clnt, P9_TREAD, "dqd", fid->fid, offset, rsize);
+ if (clnt->trans_mod->capability &&
+ clnt->trans_mod->capability(P9_CAP_GET_MAX_SG_PAGES) &&
+ (udata && !segment_eq(get_fs(), KERNEL_DS)))
+ page_direct = 1;
+
+ if (page_direct) {
+ rsize = count;
+ req = p9_client_rpc(clnt, P9_TREAD, "dqE", fid->fid, offset,
+ rsize, udata);
+ } else {
+ req = p9_client_rpc(clnt, P9_TREAD, "dqd", fid->fid, offset,
+ rsize);
+ }
+
if (IS_ERR(req)) {
err = PTR_ERR(req);
goto error;
@@ -1314,7 +1328,7 @@ p9_client_read(struct p9_fid *fid, char *data, char __user *udata, u64 offset,
memmove(data, dataptr, count);
}
- if (udata) {
+ if (udata && !page_direct) {
err = copy_to_user(udata, dataptr, count);
if (err) {
err = -EFAULT;
diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index 97f313d..b82d117 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -194,6 +194,25 @@ pdu_write_u(struct p9_fcall *pdu, struct p9_client *c, const char __user *udata,
return len;
}
+ static size_t
+pdu_write_ur(struct p9_fcall *pdu, struct p9_client *c,
+ const char __user *udata, size_t size)
+{
+ size_t len = size;
+ int max_req_sg_pages = 0;
+
+ if (c->trans_mod->capability)
+ max_req_sg_pages =
+ c->trans_mod->capability(P9_CAP_GET_MAX_SG_PAGES);
+ if (max_req_sg_pages) {
+ len = pdu_fill_pages(pdu, udata, size, 1, max_req_sg_pages);
+ if (len < 0)
+ return len;
+ pdu->pdata_read_len = len;
+ }
+ return len;
+}
+
/*
b - int8_t
w - int16_t
@@ -534,8 +553,18 @@ p9pdu_vwritef(struct p9_fcall *pdu, struct p9_client *c, const char *fmt,
if (!errcode &&
pdu_write_u(pdu, c, udata, count) < 0)
errcode = -EFAULT;
- }
- break;
+ }
+ break;
+ case 'E':{
+ int32_t count = va_arg(ap, int32_t);
+ const char __user *udata =
+ va_arg(ap, const void __user *);
+ errcode = p9pdu_writef(pdu, c, "d", count);
+ if (!errcode &&
+ pdu_write_ur(pdu, c, udata, count) < 0)
+ errcode = -EFAULT;
+ }
+ break;
case 'T':{
int16_t nwname = va_arg(ap, int);
const char **wnames = va_arg(ap, const char **);
--
1.6.5.2
--
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