>From 43c8ea2b78f31d7ccd349384a9a2084e787aafc1 Mon Sep 17 00:00:00 2001
From: Alan D. Brunelle <alan.brunelle@xxxxxx>
Date: Tue, 27 May 2008 10:32:36 -0400
Subject: [PATCH] Changed blk trace msgs to directly use relay buffer
Allows for SMP-usage without corruption, and removes an extra copy at
the expense of copying extra bytes. Reduced message size from 1024 to 128.
Signed-off-by: Alan D. Brunelle <alan.brunelle@xxxxxx>
---
block/blktrace.c | 42 ++++++++++++++++++++++++++----------------
include/linux/blktrace_api.h | 2 +-
2 files changed, 27 insertions(+), 17 deletions(-)
diff --git a/block/blktrace.c b/block/blktrace.c
index 20e11f3..38e6b83 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -27,6 +27,20 @@
static unsigned int blktrace_seq __read_mostly = 1;
+static inline void note_header(struct blk_io_trace *t, struct blk_trace *bt,
+ pid_t pid, int action, size_t len)
+{
+ const int cpu = smp_processor_id();
+
+ t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
+ t->time = ktime_to_ns(ktime_get());
+ t->device = bt->dev;
+ t->action = action;
+ t->pid = pid;
+ t->cpu = cpu;
+ t->pdu_len = len;
+}
+
/*
* Send out a notify message.
*/
@@ -37,15 +51,7 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
t = relay_reserve(bt->rchan, sizeof(*t) + len);
if (t) {
- const int cpu = smp_processor_id();
-
- t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
- t->time = ktime_to_ns(ktime_get());
- t->device = bt->dev;
- t->action = action;
- t->pid = pid;
- t->cpu = cpu;
- t->pdu_len = len;
+ note_header(t, bt, pid, action, len);
memcpy((void *) t + sizeof(*t), data, len);
}
}
@@ -77,15 +83,19 @@ static void trace_note_time(struct blk_trace *bt)
void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
{
- int n;
- va_list args;
- static char bt_msg_buf[BLK_TN_MAX_MSG];
+ struct blk_io_trace *t;
- va_start(args, fmt);
- n = vscnprintf(bt_msg_buf, BLK_TN_MAX_MSG, fmt, args);
- va_end(args);
+ t = relay_reserve(bt->rchan, sizeof(*t) + BLK_TN_MAX_MSG);
+ if (t) {
+ va_list args;
+ char *bt_msg_buf = (void *) t + sizeof(*t);
+
+ va_start(args, fmt);
+ vscnprintf(bt_msg_buf, BLK_TN_MAX_MSG, fmt, args);
+ va_end(args);
- trace_note(bt, 0, BLK_TN_MESSAGE, bt_msg_buf, n);
+ note_header(t, bt, 0, BLK_TN_MESSAGE, BLK_TN_MAX_MSG);
+ }
}
EXPORT_SYMBOL_GPL(__trace_note_message);
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index b7cd8f1..3228caa 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -172,7 +172,7 @@ extern void __trace_note_message(struct blk_trace *, const char *fmt, ...);
if (unlikely(bt)) \
__trace_note_message(bt, fmt, ##__VA_ARGS__); \
} while (0)
-#define BLK_TN_MAX_MSG 1024
+#define BLK_TN_MAX_MSG 128
/**
* blk_add_trace_rq - Add a trace for a request oriented action
--
1.5.4.3
