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net: Introduce recvmmsg socket syscall

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Meaning receive multiple messages, reducing the number of syscalls and
net stack entry/exit operations.

Next patches will introduce mechanisms where protocols that want to
optimize this operation will provide an unlocked_recvmsg operation.

This takes into account comments made by:

. Paul Moore: sock_recvmsg is called only for the first datagram,
  sock_recvmsg_nosec is used for the rest.

. Caitlin Bestler: recvmmsg now has a struct timespec timeout, that
  works in the same fashion as the ppoll one.

  If the underlying protocol returns a datagram with MSG_OOB set, this
  will make recvmmsg return right away with as many datagrams (+ the OOB
  one) it has received so far.

. Rémi Denis-Courmont & Steven Whitehouse: If we receive N < vlen
  datagrams and then recvmsg returns an error, recvmmsg will return
  the successfully received datagrams, store the error and return it
  in the next call.

This paves the way for a subsequent optimization, sk_prot->unlocked_recvmsg,
where we will be able to acquire the lock only at batch start and end, not at
every underlying recvmsg call.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Arnaldo Carvalho de Melo
2009-10-12 23:40:10 -07:00
committed by David S. Miller
parent c05e85a06e
commit a2e2725541
25 changed files with 261 additions and 50 deletions
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8
include/net/compat.h
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@@ -18,6 +18,11 @@ struct compat_msghdr {
compat_uint_t msg_flags;
};
struct compat_mmsghdr {
struct compat_msghdr msg_hdr;
compat_uint_t msg_len;
};
struct compat_cmsghdr {
compat_size_t cmsg_len;
compat_int_t cmsg_level;
@@ -35,6 +40,9 @@ extern int get_compat_msghdr(struct msghdr *, struct compat_msghdr __user *);
extern int verify_compat_iovec(struct msghdr *, struct iovec *, struct sockaddr *, int);
extern asmlinkage long compat_sys_sendmsg(int,struct compat_msghdr __user *,unsigned);
extern asmlinkage long compat_sys_recvmsg(int,struct compat_msghdr __user *,unsigned);
extern asmlinkage long compat_sys_recvmmsg(int, struct compat_mmsghdr __user *,
unsigned, unsigned,
struct timespec __user *);
extern asmlinkage long compat_sys_getsockopt(int, int, int, char __user *, int __user *);
extern int put_cmsg_compat(struct msghdr*, int, int, int, void *);