Remove duplicate typedefs from trace.h

Older versions of GCC (e.g. GCC 4.4.7 on RHEL6) do not allow duplicate
typedef declarations with the same type. The trace.h header contains
some typedefs to avoid 'unknown type' errors for C files that haven't
declared the type in question. But this causes build failures for C
files that have already declared the type. Newer versions of GCC (e.g.
v4.6) allow duplicate typedefs with the same type unless pedantic error
checking is in force. To support the older versions we need to remove
the duplicate typedefs.

Removal of the typedefs means we can't built tracepoints code using
those types unless the required headers have been included. To
facilitate this, all tracepoint event declarations have been moved out
of trace.h into separate headers. Each new header is explicitly included
from the C file that uses the events defined therein. The trace.h header
is still indirectly included form zfs_context.h and provides the
implementation of the dprintf(), dbgmsg(), and SET_ERROR() interfaces.
This makes those interfaces readily available throughout the code base.
The macros that redefine DTRACE_PROBE* to use Linux tracepoints are also
still provided by trace.h, so it is a prerequisite for the other
trace_*.h headers.

These new Linux implementation-specific headers do introduce a small
divergence from upstream ZFS in several core C files, but this should
not present a significant maintenance burden.

Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2953

module/zfs/arc.c

@@ -147,6 +147,7 @@
 #include <sys/dmu_tx.h>
 #include <zfs_fletcher.h>
 #include <sys/arc_impl.h>
+#include <sys/trace_arc.h>
 
 #ifndef _KERNEL
 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
@@ -625,11 +626,6 @@ typedef struct l2arc_read_callback {
 	enum zio_compress	l2rcb_compress;		/* applied compress */
 } l2arc_read_callback_t;
 
-typedef struct l2arc_write_callback {
-	l2arc_dev_t	*l2wcb_dev;		/* device info */
-	arc_buf_hdr_t	*l2wcb_head;		/* head of write buflist */
-} l2arc_write_callback_t;
-
 struct l2arc_buf_hdr {
 	/* protected by arc_buf_hdr  mutex */
 	l2arc_dev_t		*b_dev;		/* L2ARC device */

module/zfs/dbuf.c

@@ -43,6 +43,7 @@
 #include <sys/zfeature.h>
 #include <sys/blkptr.h>
 #include <sys/range_tree.h>
+#include <sys/trace_dbuf.h>
 
 struct dbuf_hold_impl_data {
 	/* Function arguments */

module/zfs/dmu_tx.c

@@ -38,6 +38,7 @@
 #include <sys/sa_impl.h>
 #include <sys/zfs_context.h>
 #include <sys/varargs.h>
+#include <sys/trace_dmu.h>
 
 typedef void (*dmu_tx_hold_func_t)(dmu_tx_t *tx, struct dnode *dn,
     uint64_t arg1, uint64_t arg2);

module/zfs/dnode.c

@@ -36,6 +36,7 @@
 #include <sys/zio.h>
 #include <sys/dmu_zfetch.h>
 #include <sys/range_tree.h>
+#include <sys/trace_dnode.h>
 
 static kmem_cache_t *dnode_cache;
 /*

module/zfs/dsl_pool.c

@@ -45,6 +45,7 @@
 #include <sys/zfeature.h>
 #include <sys/zil_impl.h>
 #include <sys/dsl_userhold.h>
+#include <sys/trace_txg.h>
 
 /*
  * ZFS Write Throttle

module/zfs/trace.c

@@ -37,3 +37,11 @@
 
 #define	CREATE_TRACE_POINTS
 #include <sys/trace.h>
+#include <sys/trace_acl.h>
+#include <sys/trace_arc.h>
+#include <sys/trace_dbuf.h>
+#include <sys/trace_dmu.h>
+#include <sys/trace_dnode.h>
+#include <sys/trace_txg.h>
+#include <sys/trace_zil.h>
+#include <sys/trace_zrlock.h>

module/zfs/txg.c

@@ -32,6 +32,7 @@
 #include <sys/dsl_pool.h>
 #include <sys/dsl_scan.h>
 #include <sys/callb.h>
+#include <sys/trace_txg.h>
 
 /*
  * ZFS Transaction Groups

module/zfs/zfs_acl.c

@@ -52,6 +52,7 @@
 #include <sys/dnode.h>
 #include <sys/zap.h>
 #include <sys/sa.h>
+#include <sys/trace_acl.h>
 #include "fs/fs_subr.h"
 
 #define	ALLOW	ACE_ACCESS_ALLOWED_ACE_TYPE

module/zfs/zil.c

@@ -39,6 +39,7 @@
 #include <sys/dmu_tx.h>
 #include <sys/dsl_pool.h>
 #include <sys/metaslab.h>
+#include <sys/trace_zil.h>
 
 /*
  * The zfs intent log (ZIL) saves transaction records of system calls

module/zfs/zrlock.c

@@ -37,6 +37,7 @@
  * function calls.
  */
 #include <sys/zrlock.h>
+#include <sys/trace_zrlock.h>
 
 /*
  * A ZRL can be locked only while there are zero references, so ZRL_LOCKED is