cifs: turn read_from_socket into a wrapper around a vectorized version
Eventually we'll want to allow cifsd to read data directly into the
pagecache. In order to do that we'll need a routine that can take a
kvec array and pass that directly to kernel_recvmsg.
Unfortunately though, the kernel's recvmsg routines modify the kvec
array that gets passed in, so we need to use a copy of the kvec array
and refresh that copy on each pass through the loop.
Reviewed-and-Tested-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 97a65af..4860940 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -375,14 +375,54 @@
return false;
}
+/*
+ * kvec_array_init - clone a kvec array, and advance into it
+ * @new: pointer to memory for cloned array
+ * @iov: pointer to original array
+ * @nr_segs: number of members in original array
+ * @bytes: number of bytes to advance into the cloned array
+ *
+ * This function will copy the array provided in iov to a section of memory
+ * and advance the specified number of bytes into the new array. It returns
+ * the number of segments in the new array. "new" must be at least as big as
+ * the original iov array.
+ */
+static unsigned int
+kvec_array_init(struct kvec *new, struct kvec *iov, unsigned int nr_segs,
+ size_t bytes)
+{
+ size_t base = 0;
+
+ while (bytes || !iov->iov_len) {
+ int copy = min(bytes, iov->iov_len);
+
+ bytes -= copy;
+ base += copy;
+ if (iov->iov_len == base) {
+ iov++;
+ nr_segs--;
+ base = 0;
+ }
+ }
+ memcpy(new, iov, sizeof(*iov) * nr_segs);
+ new->iov_base += base;
+ new->iov_len -= base;
+ return nr_segs;
+}
+
static int
-read_from_socket(struct TCP_Server_Info *server, char *buf,
- unsigned int to_read)
+readv_from_socket(struct TCP_Server_Info *server, struct kvec *iov_orig,
+ unsigned int nr_segs, unsigned int to_read)
{
int length = 0;
int total_read;
+ unsigned int segs;
struct msghdr smb_msg;
- struct kvec iov;
+ struct kvec *iov;
+
+ iov = kmalloc(sizeof(*iov_orig) * nr_segs, GFP_NOFS);
+ if (!iov)
+ return -ENOMEM;
smb_msg.msg_control = NULL;
smb_msg.msg_controllen = 0;
@@ -393,10 +433,11 @@
break;
}
- iov.iov_base = buf + total_read;
- iov.iov_len = to_read;
- length = kernel_recvmsg(server->ssocket, &smb_msg, &iov, 1,
- to_read, 0);
+ segs = kvec_array_init(iov, iov_orig, nr_segs, total_read);
+
+ length = kernel_recvmsg(server->ssocket, &smb_msg,
+ iov, segs, to_read, 0);
+
if (server->tcpStatus == CifsExiting) {
total_read = -ESHUTDOWN;
break;
@@ -423,9 +464,22 @@
break;
}
}
+ kfree(iov);
return total_read;
}
+static int
+read_from_socket(struct TCP_Server_Info *server, char *buf,
+ unsigned int to_read)
+{
+ struct kvec iov;
+
+ iov.iov_base = buf;
+ iov.iov_len = to_read;
+
+ return readv_from_socket(server, &iov, 1, to_read);
+}
+
static bool
is_smb_response(struct TCP_Server_Info *server, unsigned char type)
{