libceph: use kernel_sendpage() for sending zeroes

If a message queued for send gets revoked, zeroes are sent over the
wire instead of any unsent data.  This is done by constructing a
message and passing it to kernel_sendmsg() via ceph_tcp_sendmsg().

Since we are already working with a page in this case we can use
the sendpage interface instead.  Create a new ceph_tcp_sendpage()
helper that sets up flags to match the way ceph_tcp_sendmsg()
does now.

Signed-off-by: Alex Elder <elder@dreamhost.com>
Reviewed-by: Sage Weil <sage@newdream.net>

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 589b768..9207a8c 100644 (file)
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -321,6 +321,19 @@ static int ceph_tcp_sendmsg(struct socket *sock, struct kvec *iov,
        return r;
 }
 
+static int ceph_tcp_sendpage(struct socket *sock, struct page *page,
+                    int offset, size_t size, int more)
+{
+       int flags = MSG_DONTWAIT | MSG_NOSIGNAL | (more ? MSG_MORE : MSG_EOR);
+       int ret;
+
+       ret = kernel_sendpage(sock, page, offset, size, flags);
+       if (ret == -EAGAIN)
+               ret = 0;
+
+       return ret;
+}
+
 
 /*
  * Shutdown/close the socket for the given connection.
@@ -944,12 +957,9 @@ static int write_partial_skip(struct ceph_connection *con)
        int ret;
 
        while (con->out_skip > 0) {
-               struct kvec iov = {
-                       .iov_base = zero_page_address,
-                       .iov_len = min(con->out_skip, (int)PAGE_CACHE_SIZE)
-               };
+               size_t size = min(con->out_skip, (int) PAGE_CACHE_SIZE);
 
-               ret = ceph_tcp_sendmsg(con->sock, &iov, 1, iov.iov_len, 1);
+               ret = ceph_tcp_sendpage(con->sock, zero_page, 0, size, 1);
                if (ret <= 0)
                        goto out;
                con->out_skip -= ret;