From: Jens Axboe <axboe@suse.de>
Date: Fri, 21 Apr 2006 07:44:23 +0000 (+0200)
Subject: [PATCH] Add vmsplice
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=7ee0f27f5bdfc8005e497efc8336606654280def;p=splice.git

[PATCH] Add vmsplice
---

diff --git a/.gitignore b/.gitignore
index 5934fde..0b94c09 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,4 @@ splice-net
 splice-out
 splice-test4c
 splice-test4s
+vmsplice
diff --git a/Makefile b/Makefile
index 29d76a4..c9618c1 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 CC	= gcc
 CFLAGS	= -Wall -O2 -g -D_GNU_SOURCE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64
-PROGS	= ktee ktee-net splice-cp splice-in splice-out splice-net splice-test4c splice-test4s
+PROGS	= ktee ktee-net splice-cp splice-in splice-out splice-net splice-test4c splice-test4s vmsplice
 
 all: depend $(PROGS)
 
diff --git a/splice.h b/splice.h
index 0cdd1ca..e1a0592 100644
--- a/splice.h
+++ b/splice.h
@@ -4,19 +4,28 @@
 #if defined(__i386__)
 #define __NR_splice	313
 #define __NR_tee	315
+#define __NR_vmsplice	316
 #elif defined(__x86_64__)
 #define __NR_splice	275
 #define __NR_tee	276
+#define __NR_vmsplice	278
 #elif defined(__powerpc__) || defined(__powerpc64__)
 #define __NR_splice	283
 #define __NR_tee	284
+#define __NR_vmsplice	285
 #elif defined(__ia64__)
 #define __NR_splice	1297
 #define __NR_tee	1301
+#define __NR_vmsplice	1301
 #else
 #error unsupported arch
 #endif
 
+#ifndef F_SETPSZ
+#define	F_SETPSZ	15
+#define F_GETPSZ	16
+#endif
+
 #define SPLICE_F_MOVE	(0x01)	/* move pages instead of copying */
 #define SPLICE_F_NONBLOCK (0x02) /* don't block on the pipe splicing (but */
 				 /* we may still block on the fd we splice */
@@ -35,6 +44,11 @@ static inline int tee(int fdin, int fdout, size_t len, unsigned int flags)
 	return syscall(__NR_tee, fdin, fdout, len, flags);
 }
 
+static inline int vmsplice(int fd, void *buffer, size_t len, unsigned int flags)
+{
+	return syscall(__NR_vmsplice, fd, buffer, len, flags);
+}
+
 #define SPLICE_SIZE	(64*1024)
 
 #define BUG_ON(c) assert(!(c))
diff --git a/vmsplice.c b/vmsplice.c
new file mode 100644
index 0000000..be77534
--- /dev/null
+++ b/vmsplice.c
@@ -0,0 +1,105 @@
+/*
+ * Use vmsplice to fill some user memory into a pipe. vmsplice writes
+ * to stdout, so that must be a pipe.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <sys/poll.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "splice.h"
+
+#define ALIGN_BUF
+
+#ifdef ALIGN_BUF
+#define ALIGN_MASK	(65535)	/* 64k-1, should just be PAGE_SIZE - 1 */
+#define ALIGN(buf)	(void *) (((unsigned long) (buf) + ALIGN_MASK) & ~ALIGN_MASK)
+#else
+#define ALIGN_MASK	(0)
+#define ALIGN(buf)	(buf)
+#endif
+
+int do_vmsplice(int fd, void *buffer, int len)
+{
+	struct pollfd pfd = { .fd = fd, .events = POLLOUT, };
+	int written;
+
+	while (len) {
+		/*
+		 * in a real app you'd be more clever with poll of course,
+		 * here we are basically just blocking on output room and
+		 * not using the free time for anything interesting.
+		 */
+		if (poll(&pfd, 1, -1) < 0)
+			return error("poll");
+
+		written = vmsplice(fd, buffer, min(SPLICE_SIZE, len), 0);
+
+		if (written <= 0)
+			return error("vmsplice");
+
+		len -= written;
+	}
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	unsigned char *buffer;
+	struct stat sb;
+	long page_size;
+	int i, ret;
+
+	if (fstat(STDOUT_FILENO, &sb) < 0)
+		return error("stat");
+	if (!S_ISFIFO(sb.st_mode)) {
+		fprintf(stderr, "stdout must be a pipe\n");
+		return 1;
+	}
+
+	ret = fcntl(STDOUT_FILENO, F_GETPSZ);
+	if (ret < 0)
+		return error("F_GETPSZ");
+
+	page_size = sysconf(_SC_PAGESIZE);
+	if (page_size < 0)
+		return error("_SC_PAGESIZE");
+
+	fprintf(stderr, "Pipe size: %d pages / %ld bytes\n", ret, ret * page_size);
+
+	buffer = ALIGN(malloc(2 * SPLICE_SIZE + ALIGN_MASK));
+	for (i = 0; i < 2 * SPLICE_SIZE; i++)
+		buffer[i] = (i & 0xff);
+
+	do {
+		/*
+		 * vmsplice the first half of the buffer into the pipe
+		 */
+		if (do_vmsplice(STDOUT_FILENO, buffer, SPLICE_SIZE))
+			break;
+
+		/*
+		 * first half is now in pipe, but we don't quite know when
+		 * we can reuse it.
+		 */
+
+		/*
+		 * vmsplice second half
+		 */
+		if (do_vmsplice(STDOUT_FILENO, buffer + SPLICE_SIZE, SPLICE_SIZE))
+			break;
+
+		/*
+		 * We still don't know when we can reuse the second half of
+		 * the buffer, but we do now know that all parts of the first
+		 * half have been consumed from the pipe - so we can reuse that.
+		 */
+	} while (0);
+
+	return 0;
+}