tracing: fix splice return too large (93cfb3c9) · Commits · 戴 / test

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>

kernel/trace/trace.c

+14 −2

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

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

	spd.nr_pages = i;		spd.nr_pages = i;

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