Migrate the sendfile_sync structure into a public(ish) API in preparation

for extending and reusing it.

The sendfile_sync wrapper is mostly just a "mbuf transaction" wrapper,
used to indicate that the backing store for a group of mbufs has completed.
It's only being used by sendfile for now and it's only implementing a
sleep/wakeup rendezvous.  However, there are other potential signaling
paths (kqueue) and other potential uses (socket zero-copy write) where the
same mechanism would also be useful.

So, with that in mind:

* extract the sendfile_sync code out into sf_sync_*() methods
* teach the sf_sync_alloc method about the current config flag -
  it will eventually know about kqueue.
* move the sendfile_sync code out of do_sendfile() - the only thing
  it now knows about is the sfs pointer.  The guts of the sync
  rendezvous (setup, rendezvous/wait, free) is now done in the
  syscall wrapper.
* .. and teach the 32-bit compat sendfile call the same.

This should be a no-op.  It's primarily preparation work for teaching
the sendfile_sync about kqueue notification.

Tested:

* Peter Holm's sendfile stress / regression scripts

Sponsored by:	Netflix, Inc.

1 files changed, 19 insertions, 1 deletions

diff --git a/sys/compat/freebsd32/freebsd32_misc.c b/sys/compat/freebsd32/freebsd32_misc.c
index 0703fd3..3b26745 100644
--- a/sys/compat/freebsd32/freebsd32_misc.c
+++ b/sys/compat/freebsd32/freebsd32_misc.c
@@ -83,6 +83,9 @@ __FBSDID("$FreeBSD$");
 #include <sys/msg.h>
 #include <sys/sem.h>
 #include <sys/shm.h>
+#include <sys/condvar.h>
+#include <sys/sf_buf.h>
+#include <sys/sf_sync.h>
 
 #ifdef INET
 #include <netinet/in.h>
@@ -1653,12 +1656,14 @@ freebsd32_do_sendfile(struct thread *td,
 	off_t offset;
 	int error;
 	off_t sbytes;
+	struct sendfile_sync *sfs;
 
 	offset = PAIR32TO64(off_t, uap->offset);
 	if (offset < 0)
 		return (EINVAL);
 
 	hdr_uio = trl_uio = NULL;
+	sfs = NULL;
 
 	if (uap->hdtr != NULL) {
 		error = copyin(uap->hdtr, &hdtr32, sizeof(hdtr32));
@@ -1692,8 +1697,21 @@ freebsd32_do_sendfile(struct thread *td,
 		goto out;
 	}
 
+	/*
+	 * If we need to wait for completion, initialise the sfsync
+	 * state here.
+	 */
+	if (uap->flags & SF_SYNC)
+		sfs = sf_sync_alloc(uap->flags & SF_SYNC);
+
 	error = fo_sendfile(fp, uap->s, hdr_uio, trl_uio, offset,
-	    uap->nbytes, &sbytes, uap->flags, compat ? SFK_COMPAT : 0, td);
+	    uap->nbytes, &sbytes, uap->flags, compat ? SFK_COMPAT : 0,
+	    sfs, td);
+	if (sfs != NULL) {
+		sf_sync_syscall_wait(sfs);
+		sf_sync_free(sfs);
+	}
+
 	fdrop(fp, td);
 	if (uap->sbytes != NULL)
 		copyout(&sbytes, uap->sbytes, sizeof(off_t));