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Subject[PATCH 1/7] ring-buffer: use BUF_PAGE_HDR_SIZE in calculating index
From: Steven Rostedt <srostedt@redhat.com>

The index of the event is found by masking PAGE_MASK to it and
subtracting the header size. Currently the header size is calculate
by PAGE_SIZE - BUF_PAGE_SIZE, when we already have a macro
BUF_PAGE_HDR_SIZE to define it.

If we want to change BUF_PAGE_SIZE to something less than filling
the rest of the page (this is done for debugging), then we break
the algorithm to find the index.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/ring_buffer.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index ed35599..6b17a11 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1013,7 +1013,7 @@ rb_event_index(struct ring_buffer_event *event)
{
unsigned long addr = (unsigned long)event;

- return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
+ return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
}

static inline int
--
1.6.3.1
--


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