From: Julien Desfossez <jdesfossez@efficios.com>
Date: Mon, 11 Dec 2017 21:58:51 +0000 (-0500)
Subject: Support to dump the kernel metadata cache from the beginning
X-Git-Url: http://git.efficios.com/?p=lttng-tools.git;a=commitdiff_plain;h=8024cc8c4f2b6b0413b2e8d5b5bf01024a91a337

Support to dump the kernel metadata cache from the beginning

On demand, the consumer can ask for the kernel tracer to dump the
content of the metadata cache (depends on lttng-modules 2.11). This
allows to extract the exact same metadata (compared to regenerating it
which could change the epoch offset).

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/common/kernel-ctl/kernel-ctl.c b/src/common/kernel-ctl/kernel-ctl.c
index 6a256fefd..a495ca9b7 100644
--- a/src/common/kernel-ctl/kernel-ctl.c
+++ b/src/common/kernel-ctl/kernel-ctl.c
@@ -419,6 +419,10 @@ int kernctl_get_metadata_version(int fd, uint64_t *version)
 	return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_GET_METADATA_VERSION, version);
 }
 
+int kernctl_metadata_cache_dump(int fd)
+{
+	return LTTNG_IOCTL_CHECK(fd, RING_BUFFER_METADATA_CACHE_DUMP);
+}
 
 /* Buffer operations */
 
diff --git a/src/common/kernel-ctl/kernel-ctl.h b/src/common/kernel-ctl/kernel-ctl.h
index d88f5e765..fbb273190 100644
--- a/src/common/kernel-ctl/kernel-ctl.h
+++ b/src/common/kernel-ctl/kernel-ctl.h
@@ -95,6 +95,7 @@ int kernctl_put_subbuf(int fd);
 int kernctl_buffer_flush(int fd);
 int kernctl_buffer_flush_empty(int fd);
 int kernctl_get_metadata_version(int fd, uint64_t *version);
+int kernctl_metadata_cache_dump(int fd);
 
 /* index */
 int kernctl_get_timestamp_begin(int fd, uint64_t *timestamp_begin);
diff --git a/src/common/kernel-ctl/kernel-ioctl.h b/src/common/kernel-ctl/kernel-ioctl.h
index 3c4f4129e..4ab0eabbc 100644
--- a/src/common/kernel-ctl/kernel-ioctl.h
+++ b/src/common/kernel-ctl/kernel-ioctl.h
@@ -59,6 +59,11 @@
 #define RING_BUFFER_SNAPSHOT_SAMPLE_POSITIONS	_IO(0xF6, 0x0E)
 /* Flush the current sub-buffer, even if empty. */
 #define RING_BUFFER_FLUSH_EMPTY			_IO(0xF6, 0x0F)
+/*
+ * Reset the position of what has been consumed from the metadata cache to 0
+ * so it can be read again.
+ */
+#define RING_BUFFER_METADATA_CACHE_DUMP    	_IO(0xF6, 0x10)
 
 /* returns the timestamp begin of the current sub-buffer */
 #define LTTNG_RING_BUFFER_GET_TIMESTAMP_BEGIN     _IOR(0xF6, 0x20, uint64_t)