Commit 93cfb3c9 authored Apr 02, 2009 by Lai Jiangshan Committed by Ingo Molnar Apr 10, 2009

tracing: fix splice return too large



I got these from strace:

 splice(0x3, 0, 0x5, 0, 0x1000, 0x1) = 12288
 splice(0x3, 0, 0x5, 0, 0x1000, 0x1) = 12288
 splice(0x3, 0, 0x5, 0, 0x1000, 0x1) = 12288
 splice(0x3, 0, 0x5, 0, 0x1000, 0x1) = 16384
 splice(0x3, 0, 0x5, 0, 0x1000, 0x1) = 8192
 splice(0x3, 0, 0x5, 0, 0x1000, 0x1) = 8192
 splice(0x3, 0, 0x5, 0, 0x1000, 0x1) = 8192

I wanted to splice_read 4096 bytes, but it returns 8192 or larger.

It is because the return value of tracing_buffers_splice_read()
does not include "zero out any left over data" bytes.

But tracing_buffers_read() includes these bytes, we make them
consistent.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <srostedt@redhat.com>
LKML-Reference: <49D46674.9030804@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent c7625a55

kernel/trace/trace.c

+14 −2

Original line number	Diff line number	Diff line
		@@ -3428,7 +3428,19 @@ tracing_buffers_splice_read(struct file file, loff_t ppos,
		int size, i;
		size_t ret;

		for (i = 0; i < PIPE_BUFFERS && len; i++, len -= size) {
		if (*ppos & (PAGE_SIZE - 1)) {
		WARN_ONCE(1, "Ftrace: previous read must page-align\n");
		return -EINVAL;
		}

		if (len & (PAGE_SIZE - 1)) {
		WARN_ONCE(1, "Ftrace: splice_read should page-align\n");
		if (len < PAGE_SIZE)
		return -EINVAL;
		len &= PAGE_MASK;
		}

		for (i = 0; i < PIPE_BUFFERS && len; i++, len -= PAGE_SIZE) {
		struct page *page;
		int r;

		@@ -3467,7 +3479,7 @@ tracing_buffers_splice_read(struct file file, loff_t ppos,
		spd.partial[i].offset = 0;
		spd.partial[i].private = (unsigned long)ref;
		spd.nr_pages++;
		*ppos += size;
		*ppos += PAGE_SIZE;
		}

		spd.nr_pages = i;