Linux 6.10 compat: Fix tracepoints definitions

__string field definition includes the source variable for a value
of the string when the TP hits; in 6.10+ kernels, __assign_str()
uses that to copy a value from src to the string, with older
kernels, __assign_str still accepted src as a second parameter.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Pavel Snajdr <[email protected]>
Co-authored-by: Tony Hutter <[email protected]>
Closes #16475 
Closes #16515

Author: snajpa

config/kernel-assign_str.m4

@@ -0,0 +1,62 @@
+dnl #
+dnl # 6.10 kernel, check number of args of __assign_str() for trace:
+dnl
+dnl # 6.10+:           one arg
+dnl # 6.9 and older:   two args
+dnl #
+dnl # More specifically, this will test to see if __assign_str() takes one
+dnl # arg.  If __assign_str() takes two args, or is not defined, then
+dnl # HAVE_1ARG_ASSIGN_STR will not be set.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_1ARG_ASSIGN_STR], [
+       AC_MSG_CHECKING([whether __assign_str() has one arg])
+       ZFS_LINUX_TRY_COMPILE_HEADER([
+               #include <linux/module.h>
+               MODULE_LICENSE("$ZFS_META_LICENSE");
+
+               #define CREATE_TRACE_POINTS
+               #include "conftest.h"
+       ],[
+               trace_zfs_autoconf_event_one("1");
+               trace_zfs_autoconf_event_two("2");
+       ],[
+               AC_MSG_RESULT(yes)
+               AC_DEFINE(HAVE_1ARG_ASSIGN_STR, 1,
+                   [__assign_str() has one arg])
+       ],[
+               AC_MSG_RESULT(no)
+       ],[
+               #if !defined(_CONFTEST_H) || defined(TRACE_HEADER_MULTI_READ)
+               #define _CONFTEST_H
+
+               #undef  TRACE_SYSTEM
+               #define TRACE_SYSTEM zfs
+               #include <linux/tracepoint.h>
+
+               DECLARE_EVENT_CLASS(zfs_autoconf_event_class,
+                       TP_PROTO(char *string),
+                       TP_ARGS(string),
+                       TP_STRUCT__entry(
+                               __string(str, string)
+                       ),
+                       TP_fast_assign(
+                               __assign_str(str);
+                       ),
+                       TP_printk("str = %s", __get_str(str))
+               );
+
+               #define DEFINE_AUTOCONF_EVENT(name) \
+               DEFINE_EVENT(zfs_autoconf_event_class, name, \
+                       TP_PROTO(char * str), \
+                       TP_ARGS(str))
+               DEFINE_AUTOCONF_EVENT(zfs_autoconf_event_one);
+               DEFINE_AUTOCONF_EVENT(zfs_autoconf_event_two);
+
+               #endif /* _CONFTEST_H */
+
+               #undef  TRACE_INCLUDE_PATH
+               #define TRACE_INCLUDE_PATH .
+               #define TRACE_INCLUDE_FILE conftest
+               #include <trace/define_trace.h>
+       ])
+])

config/kernel.m4

@@ -332,6 +332,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_SYNC_BDEV
 	ZFS_AC_KERNEL_MM_PAGE_SIZE
 	ZFS_AC_KERNEL_MM_PAGE_MAPPING
+	ZFS_AC_KERNEL_1ARG_ASSIGN_STR
 	case "$host_cpu" in
 		powerpc*)
 			ZFS_AC_KERNEL_CPU_HAS_FEATURE

include/os/linux/spl/sys/types.h

@@ -83,4 +83,10 @@ typedef struct user_namespace	zidmap_t;
 
 extern zidmap_t *zfs_init_idmap;
 
+#ifdef HAVE_1ARG_ASSIGN_STR
+#define	__assign_str_impl(a, b)		__assign_str(a)
+#else
+#define	__assign_str_impl(a, b)		__assign_str(a, b)
+#endif
+
 #endif	/* _SPL_TYPES_H */

include/os/linux/zfs/sys/trace_dbgmsg.h

@@ -32,6 +32,7 @@
 #define	_TRACE_DBGMSG_H
 
 #include <linux/tracepoint.h>
+#include <sys/types.h>
 
 /*
  * This file defines tracepoint events for use by the dbgmsg(),
@@ -59,7 +60,7 @@ DECLARE_EVENT_CLASS(zfs_dprintf_class,
 	    __string(msg, msg)
 	),
 	TP_fast_assign(
-	    __assign_str(msg, msg);
+	    __assign_str_impl(msg, msg);
 	),
 	TP_printk("%s", __get_str(msg))
 );

include/os/linux/zfs/sys/trace_dbuf.h

@@ -45,28 +45,25 @@
  *     dmu_buf_impl_t *, ...,
  *     zio_t *, ...);
  */
+#define	DBUF_TP_STRUCT_ENTRY_OS_SPA \
+	    (db != NULL && \
+		POINTER_IS_VALID(DB_DNODE(db)->dn_objset)) \
+	    ? spa_name(DB_DNODE(db)->dn_objset->os_spa) : "NULL"
 
 #define	DBUF_TP_STRUCT_ENTRY					\
-	__dynamic_array(char,	os_spa,	TRACE_DBUF_MSG_MAX)	\
+	__string(os_spa, DBUF_TP_STRUCT_ENTRY_OS_SPA)		\
 	__field(uint64_t,	ds_object)			\
 	__field(uint64_t,	db_object)			\
 	__field(uint64_t,	db_level)			\
 	__field(uint64_t,	db_blkid)			\
 	__field(uint64_t,	db_offset)			\
 	__field(uint64_t,	db_size)			\
 	__field(uint64_t,	db_state)			\
-	__field(int64_t,	db_holds)			\
-	__dynamic_array(char,	msg,	TRACE_DBUF_MSG_MAX)
+	__field(int64_t,	db_holds)
 
 #define	DBUF_TP_FAST_ASSIGN						\
 	if (db != NULL) {						\
-		if (POINTER_IS_VALID(DB_DNODE(db)->dn_objset)) {	\
-			__assign_str(os_spa,				\
-			spa_name(DB_DNODE(db)->dn_objset->os_spa));	\
-		} else {						\
-			__assign_str(os_spa, "NULL");			\
-		}							\
-									\
+		__assign_str_impl(os_spa, DBUF_TP_STRUCT_ENTRY_OS_SPA); \
 		__entry->ds_object = db->db_objset->os_dsl_dataset ?	\
 		db->db_objset->os_dsl_dataset->ds_object : 0;		\
 									\
@@ -77,10 +74,8 @@
 		__entry->db_size   = db->db.db_size;			\
 		__entry->db_state  = db->db_state;			\
 		__entry->db_holds  = zfs_refcount_count(&db->db_holds);	\
-		snprintf(__get_str(msg), TRACE_DBUF_MSG_MAX,		\
-		    DBUF_TP_PRINTK_FMT, DBUF_TP_PRINTK_ARGS);		\
 	} else {							\
-		__assign_str(os_spa, "NULL");				\
+		__assign_str_impl(os_spa, DBUF_TP_STRUCT_ENTRY_OS_SPA); \
 		__entry->ds_object = 0;					\
 		__entry->db_object = 0;					\
 		__entry->db_level  = 0;					\
@@ -89,8 +84,6 @@
 		__entry->db_size   = 0;					\
 		__entry->db_state  = 0;					\
 		__entry->db_holds  = 0;					\
-		snprintf(__get_str(msg), TRACE_DBUF_MSG_MAX,		\
-		    "dbuf { NULL }");					\
 	}
 
 #define	DBUF_TP_PRINTK_FMT						\
@@ -109,15 +102,15 @@ DECLARE_EVENT_CLASS(zfs_dbuf_class,
 	TP_ARGS(db, zio),
 	TP_STRUCT__entry(DBUF_TP_STRUCT_ENTRY),
 	TP_fast_assign(DBUF_TP_FAST_ASSIGN),
-	TP_printk("%s", __get_str(msg))
+	TP_printk(DBUF_TP_PRINTK_FMT, DBUF_TP_PRINTK_ARGS)
 );
 
 DECLARE_EVENT_CLASS(zfs_dbuf_state_class,
 	TP_PROTO(dmu_buf_impl_t *db, const char *why),
 	TP_ARGS(db, why),
 	TP_STRUCT__entry(DBUF_TP_STRUCT_ENTRY),
 	TP_fast_assign(DBUF_TP_FAST_ASSIGN),
-	TP_printk("%s", __get_str(msg))
+	TP_printk(DBUF_TP_PRINTK_FMT, DBUF_TP_PRINTK_ARGS)
 );
 /* END CSTYLED */
 
@@ -139,7 +132,7 @@ DECLARE_EVENT_CLASS(zfs_dbuf_evict_one_class,
 	TP_ARGS(db, mls),
 	TP_STRUCT__entry(DBUF_TP_STRUCT_ENTRY),
 	TP_fast_assign(DBUF_TP_FAST_ASSIGN),
-	TP_printk("%s", __get_str(msg))
+	TP_printk(DBUF_TP_PRINTK_FMT, DBUF_TP_PRINTK_ARGS)
 );
 /* END CSTYLED */