Linux 3.1 compat, kern_path_parent()

Prior to Linux 3.1 the kern_path_parent symbol was exported for
use by kernel modules.  As of Linux 3.1 it is now longer easily
available.  To handle this case the spl will now dynamically
look up address of the missing symbol at module load time.

Signed-off-by: Brian Behlendorf <[email protected]>
Issue #52

7 files changed, 152 insertions, 19 deletions

diff --git a/config/spl-build.m4 b/config/spl-build.m4
index c046db830..f5696b943 100644
--- a/config/spl-build.m4
+++ b/config/spl-build.m4
@@ -80,7 +80,8 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
 	SPL_AC_KERNEL_2ARGS_INVALIDATE_INODES
 	SPL_AC_SHRINK_DCACHE_MEMORY
 	SPL_AC_SHRINK_ICACHE_MEMORY
-	SPL_AC_KERN_PATH_PARENT
+	SPL_AC_KERN_PATH_PARENT_HEADER
+	SPL_AC_KERN_PATH_PARENT_SYMBOL
 	SPL_AC_2ARGS_ZLIB_DEFLATE_WORKSPACESIZE
 	SPL_AC_SHRINK_CONTROL_STRUCT
 ])
@@ -588,6 +589,30 @@ AC_DEFUN([SPL_CHECK_SYMBOL_EXPORT],
 ])
 
 dnl #
+dnl # SPL_CHECK_SYMBOL_HEADER
+dnl # check if a symbol prototype is defined in listed headers.
+dnl #
+AC_DEFUN([SPL_CHECK_SYMBOL_HEADER], [
+	AC_MSG_CHECKING([whether symbol $1 exists in header])
+	header=0
+	for file in $3; do
+		grep -q "$2" "$LINUX/$file" 2>/dev/null
+		rc=$?
+	        if test $rc -eq 0; then
+	                header=1
+	                break;
+	        fi
+	done
+	if test $header -eq 0; then
+		AC_MSG_RESULT([no])
+		$5
+	else
+		AC_MSG_RESULT([yes])
+		$4
+	fi
+])
+
+dnl #
 dnl # SPL_CHECK_HEADER
 dnl # check whether header exists and define HAVE_$2_HEADER
 dnl #
@@ -1809,11 +1834,27 @@ dnl # and the flags argument has been removed.  The only behavior now
 dnl # offered is that of LOOKUP_PARENT.  The spl already always passed
 dnl # this flag so dropping the flag does not impact us.
 dnl #
-AC_DEFUN([SPL_AC_KERN_PATH_PARENT], [
+AC_DEFUN([SPL_AC_KERN_PATH_PARENT_HEADER], [
+	SPL_CHECK_SYMBOL_HEADER(
+		[kern_path_parent],
+		[int kern_path_parent(const char \*, struct nameidata \*)],
+		[include/linux/namei.h],
+		[AC_DEFINE(HAVE_KERN_PATH_PARENT_HEADER, 1,
+		[kern_path_parent() is available])],
+		[])
+])
+
+dnl #
+dnl # 3.1 API compat,
+dnl # The kern_path_parent() symbol is no longer exported by the kernel.
+dnl # However, it remains the prefered interface and since we still have
+dnl # access to the prototype we dynamically lookup the required address.
+dnl #
+AC_DEFUN([SPL_AC_KERN_PATH_PARENT_SYMBOL], [
 	SPL_CHECK_SYMBOL_EXPORT(
 		[kern_path_parent],
 		[fs/namei.c],
-		[AC_DEFINE(HAVE_KERN_PATH_PARENT, 1,
+		[AC_DEFINE(HAVE_KERN_PATH_PARENT_SYMBOL, 1,
 		[kern_path_parent() is available])],
 		[])
 ])
diff --git a/configure b/configure
index 1369ca05d..beeb6d59d 100755
--- a/configure
+++ b/configure
@@ -15684,6 +15684,34 @@ _ACEOF
 
 
 
+
+	{ $as_echo "$as_me:$LINENO: checking whether symbol kern_path_parent exists in header" >&5
+$as_echo_n "checking whether symbol kern_path_parent exists in header... " >&6; }
+	header=0
+	for file in include/linux/namei.h; do
+		grep -q "int kern_path_parent(const char \*, struct nameidata \*)" "$LINUX/$file" 2>/dev/null
+		rc=$?
+	        if test $rc -eq 0; then
+	                header=1
+	                break;
+	        fi
+	done
+	if test $header -eq 0; then
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+	else
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_KERN_PATH_PARENT_HEADER 1
+_ACEOF
+
+	fi
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether symbol kern_path_parent is exported" >&5
 $as_echo_n "checking whether symbol kern_path_parent is exported... " >&6; }
 	grep -q -E '[[:space:]]kern_path_parent[[:space:]]' \
@@ -15709,7 +15737,7 @@ $as_echo "no" >&6; }
 $as_echo "yes" >&6; }
 
 cat >>confdefs.h <<\_ACEOF
-#define HAVE_KERN_PATH_PARENT 1
+#define HAVE_KERN_PATH_PARENT_SYMBOL 1
 _ACEOF
 
 		fi
@@ -15718,7 +15746,7 @@ _ACEOF
 $as_echo "yes" >&6; }
 
 cat >>confdefs.h <<\_ACEOF
-#define HAVE_KERN_PATH_PARENT 1
+#define HAVE_KERN_PATH_PARENT_SYMBOL 1
 _ACEOF
 
 	fi
@@ -19885,6 +19913,34 @@ _ACEOF
 
 
 
+
+	{ $as_echo "$as_me:$LINENO: checking whether symbol kern_path_parent exists in header" >&5
+$as_echo_n "checking whether symbol kern_path_parent exists in header... " >&6; }
+	header=0
+	for file in include/linux/namei.h; do
+		grep -q "int kern_path_parent(const char \*, struct nameidata \*)" "$LINUX/$file" 2>/dev/null
+		rc=$?
+	        if test $rc -eq 0; then
+	                header=1
+	                break;
+	        fi
+	done
+	if test $header -eq 0; then
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+	else
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_KERN_PATH_PARENT_HEADER 1
+_ACEOF
+
+	fi
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether symbol kern_path_parent is exported" >&5
 $as_echo_n "checking whether symbol kern_path_parent is exported... " >&6; }
 	grep -q -E '[[:space:]]kern_path_parent[[:space:]]' \
@@ -19910,7 +19966,7 @@ $as_echo "no" >&6; }
 $as_echo "yes" >&6; }
 
 cat >>confdefs.h <<\_ACEOF
-#define HAVE_KERN_PATH_PARENT 1
+#define HAVE_KERN_PATH_PARENT_SYMBOL 1
 _ACEOF
 
 		fi
@@ -19919,7 +19975,7 @@ _ACEOF
 $as_echo "yes" >&6; }
 
 cat >>confdefs.h <<\_ACEOF
-#define HAVE_KERN_PATH_PARENT 1
+#define HAVE_KERN_PATH_PARENT_SYMBOL 1
 _ACEOF
 
 	fi
diff --git a/include/linux/file_compat.h b/include/linux/file_compat.h
index 97bd76396..d5fb2bc60 100644
--- a/include/linux/file_compat.h
+++ b/include/linux/file_compat.h
@@ -67,11 +67,17 @@ spl_filp_open(const char *name, int flags, int mode, int *err)
 #define spl_inode_unlock(ip)		(up(&(ip)->i_sem))
 #endif /* HAVE_INODE_I_MUTEX */
 
-#ifdef HAVE_KERN_PATH_PARENT
-#define spl_kern_path_parent(path, nd)	kern_path_parent(path, nd)
+#ifdef HAVE_KERN_PATH_PARENT_HEADER
+# ifndef HAVE_KERN_PATH_PARENT_SYMBOL
+typedef int (*kern_path_parent_t)(const char *, struct nameidata *);
+extern kern_path_parent_t kern_path_parent_fn;
+#  define spl_kern_path_parent(path, nd)	kern_path_parent_fn(path, nd)
+# else
+#  define spl_kern_path_parent(path, nd)	kern_path_parent(path, nd)
+# endif /* HAVE_KERN_PATH_PARENT_SYMBOL */
 #else
-#define spl_kern_path_parent(path, nd)	path_lookup(path, LOOKUP_PARENT, nd)
-#endif /* HAVE_KERN_PATH_PARENT */
+# define spl_kern_path_parent(path, nd)	path_lookup(path, LOOKUP_PARENT, nd)
+#endif /* HAVE_KERN_PATH_PARENT_HEADER */
 
 #endif /* SPL_FILE_COMPAT_H */
 
diff --git a/include/sys/vnode.h b/include/sys/vnode.h
index 36605ca4a..03462bd70 100644
--- a/include/sys/vnode.h
+++ b/include/sys/vnode.h
@@ -189,8 +189,9 @@ extern file_t *vn_getf(int fd);
 extern void vn_releasef(int fd);
 extern int vn_set_pwd(const char *filename);
 
-int vn_init(void);
-void vn_fini(void);
+int spl_vn_init_kallsyms_lookup(void);
+int spl_vn_init(void);
+void spl_vn_fini(void);
 
 #define VOP_CLOSE				vn_close
 #define VOP_SEEK				vn_seek
diff --git a/module/spl/spl-generic.c b/module/spl/spl-generic.c
index 1dedf76cf..3f042cc0d 100644
--- a/module/spl/spl-generic.c
+++ b/module/spl/spl-generic.c
@@ -561,7 +561,7 @@ __init spl_init(void)
 	if ((rc = spl_taskq_init()))
 		SGOTO(out4, rc);
 
-	if ((rc = vn_init()))
+	if ((rc = spl_vn_init()))
 		SGOTO(out5, rc);
 
 	if ((rc = proc_init()))
@@ -594,6 +594,9 @@ __init spl_init(void)
 	if ((rc = spl_kmem_init_kallsyms_lookup()))
 		SGOTO(out10, rc);
 
+	if ((rc = spl_vn_init_kallsyms_lookup()))
+		SGOTO(out10, rc);
+
 	printk(KERN_NOTICE "SPL: Loaded module v%s%s, using hostid 0x%08x\n",
 	       SPL_META_VERSION, SPL_DEBUG_STR, (unsigned int) spl_hostid);
 	SRETURN(rc);
@@ -606,7 +609,7 @@ out8:
 out7:
 	proc_fini();
 out6:
-	vn_fini();
+	spl_vn_fini();
 out5:
 	spl_taskq_fini();
 out4:
@@ -634,7 +637,7 @@ spl_fini(void)
 	tsd_fini();
 	kstat_fini();
 	proc_fini();
-	vn_fini();
+	spl_vn_fini();
 	spl_taskq_fini();
 	spl_rw_fini();
 	spl_mutex_fini();
diff --git a/module/spl/spl-vnode.c b/module/spl/spl-vnode.c
index 354e8798b..cd0fa2cd1 100644
--- a/module/spl/spl-vnode.c
+++ b/module/spl/spl-vnode.c
@@ -42,6 +42,13 @@ static spl_kmem_cache_t *vn_file_cache;
 static DEFINE_SPINLOCK(vn_file_lock);
 static LIST_HEAD(vn_file_list);
 
+#ifdef HAVE_KERN_PATH_PARENT_HEADER
+#ifndef HAVE_KERN_PATH_PARENT_SYMBOL
+kern_path_parent_t kern_path_parent_fn = SYMBOL_POISON;
+EXPORT_SYMBOL(kern_path_parent_fn);
+#endif /* HAVE_KERN_PATH_PARENT_SYMBOL */
+#endif /* HAVE_KERN_PATH_PARENT_HEADER */
+
 vtype_t
 vn_mode_to_vtype(mode_t mode)
 {
@@ -789,8 +796,24 @@ vn_file_cache_destructor(void *buf, void *cdrarg)
 	mutex_destroy(&fp->f_lock);
 } /* vn_file_cache_destructor() */
 
+int spl_vn_init_kallsyms_lookup(void)
+{
+#ifdef HAVE_KERN_PATH_PARENT_HEADER
+#ifndef HAVE_KERN_PATH_PARENT_SYMBOL
+	kern_path_parent_fn = (kern_path_parent_t)
+		spl_kallsyms_lookup_name("kern_path_parent");
+	if (!kern_path_parent_fn) {
+		printk(KERN_ERR "Error: Unknown symbol kern_path_parent\n");
+		return -EFAULT;
+	}
+#endif /* HAVE_KERN_PATH_PARENT_SYMBOL */
+#endif /* HAVE_KERN_PATH_PARENT_HEADER */
+
+	return (0);
+}
+
 int
-vn_init(void)
+spl_vn_init(void)
 {
 	SENTRY;
 	vn_cache = kmem_cache_create("spl_vn_cache",
@@ -808,7 +831,7 @@ vn_init(void)
 } /* vn_init() */
 
 void
-vn_fini(void)
+spl_vn_fini(void)
 {
         file_t *fp, *next_fp;
 	int leaked = 0;
diff --git a/spl_config.h.in b/spl_config.h.in
index 97f0e06f3..612205969 100644
--- a/spl_config.h.in
+++ b/spl_config.h.in
@@ -115,7 +115,10 @@
 #undef HAVE_KALLSYMS_LOOKUP_NAME
 
 /* kern_path_parent() is available */
-#undef HAVE_KERN_PATH_PARENT
+#undef HAVE_KERN_PATH_PARENT_HEADER
+
+/* kern_path_parent() is available */
+#undef HAVE_KERN_PATH_PARENT_SYMBOL
 
 /* kmalloc_node() is available */
 #undef HAVE_KMALLOC_NODE