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libceph: use MSG_TRUNC for discarding received bytes

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Avoid a copy into the "skip buffer".

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Ilya Dryomov 2018-04-27 18:58:47 +02:00
parent d2935d6f75
commit e5c9388399
1 changed files with 8 additions and 13 deletions
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21
net/ceph/messenger.c
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@ -168,12 +168,6 @@ static char tag_keepalive2 = CEPH_MSGR_TAG_KEEPALIVE2;
static struct lock_class_key socket_class;
#endif
/*
* When skipping (ignoring) a block of input we read it into a "skip
* buffer," which is this many bytes in size.
*/
#define SKIP_BUF_SIZE 1024
static void queue_con(struct ceph_connection *con);
static void cancel_con(struct ceph_connection *con);
static void ceph_con_workfn(struct work_struct *);
@ -520,12 +514,18 @@ static int ceph_tcp_connect(struct ceph_connection *con)
return 0;
}
/*
* If @buf is NULL, discard up to @len bytes.
*/
static int ceph_tcp_recvmsg(struct socket *sock, void *buf, size_t len)
{
struct kvec iov = {buf, len};
struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL };
int r;
if (!buf)
msg.msg_flags |= MSG_TRUNC;
iov_iter_kvec(&msg.msg_iter, READ | ITER_KVEC, &iov, 1, len);
r = sock_recvmsg(sock, &msg, msg.msg_flags);
if (r == -EAGAIN)
@ -2717,16 +2717,11 @@ static int try_read(struct ceph_connection *con)
if (con->in_base_pos < 0) {
/*
* skipping + discarding content.
*
* FIXME: there must be a better way to do this!
*/
static char buf[SKIP_BUF_SIZE];
int skip = min((int) sizeof (buf), -con->in_base_pos);
dout("skipping %d / %d bytes\n", skip, -con->in_base_pos);
ret = ceph_tcp_recvmsg(con->sock, buf, skip);
ret = ceph_tcp_recvmsg(con->sock, NULL, -con->in_base_pos);
if (ret <= 0)
goto out;
dout("skipped %d / %d bytes\n", ret, -con->in_base_pos);
con->in_base_pos += ret;
if (con->in_base_pos)
goto more;