Add .zfs control directory

This is still a work in progress, I would say it's roughly 90%
complete but it needs additional testing, verification, and some
more cleanup.  However, it's in good enough shape to start getting
some feedback on.  I've done testing with RHEL6.2 where everything
works, but there are a few lingering issues:

1) The .zfs/snapshot directory automount support requires a 2.6.37
   or newer kernel.  The exception is RHEL6.2 which has backported
   the d_automount patches.  Support for older kernels is possible
   with follow_link() but it needs to be done carefully.  Getting
   all the reference counting right and avoiding GPL-only functions
   will be tricky.

2) Support for mkdir/rmdir/mv has been implemented in the
   .zfs/snapshap directory just like Solaris but it needs more
   testing.  This functionality is only available to root until
   zfs delegations are finished.

      * mkdir - create a snapshot
      * rmdir - destroy a snapshot
      * mv    - rename a snapshot

3) The .zfs/shares directory is created but none of the smb
   functionality is implemented.

4) No testing via nfs over zfs has yet been done.  However, I did
   lay the ground work such that we should be able to traverse in
   in to the .zfs directory successfully.  It's mainly a matter
   of trying it and fixing the problems.

5) It's currently unsafe to manually unmount an automounted snapshot
   before it expires.  This should be an unlikely even since the
   mounts are suppressed from /etc/mtab but we still need to handle
   it safely.  My feeling is the best way to go about this will be
   to rework the unmount path so that the zfs_umount() call for a
   snapshot removes the matching entry from the parent z_ctldir_snaps
   tree.  This should allow for additional cleanup of the tree
   insertion/removal code since all removals manual and automatic
   will use the same call path.

6) As for cleanup I don't care for having to set MNT_SHRINKABLE in
   zpl_getattr().  We should be able to acheive this in the mount
   function by using follow_down() to get the new vfsmount.  We
   could then correctly return this instead of signaling a race
   by returning NULL.  However, getting the reference counting
   right might be tricky.  This could also be done when the code
   is refactored to support follow_link().

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue openzfs#173

Makefile.in

@@ -54,6 +54,7 @@ subdir = .
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/Makefile.in

@@ -39,6 +39,7 @@ DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/mount_zfs/Makefile.in

@@ -42,6 +42,7 @@ subdir = cmd/mount_zfs
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/sas_switch_id/Makefile.in

@@ -41,6 +41,7 @@ DIST_COMMON = $(dist_udev_SCRIPTS) $(srcdir)/Makefile.am \
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/zdb/Makefile.in

@@ -42,6 +42,7 @@ subdir = cmd/zdb
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/zfs/Makefile.in

@@ -42,6 +42,7 @@ subdir = cmd/zfs
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/zinject/Makefile.in

@@ -42,6 +42,7 @@ subdir = cmd/zinject
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/zpios/Makefile.in

@@ -42,6 +42,7 @@ subdir = cmd/zpios
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/zpool/Makefile.in

@@ -42,6 +42,7 @@ subdir = cmd/zpool
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/zpool_id/Makefile.in

@@ -41,6 +41,7 @@ DIST_COMMON = $(dist_udev_SCRIPTS) $(srcdir)/Makefile.am \
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/zpool_layout/Makefile.in

@@ -41,6 +41,7 @@ DIST_COMMON = $(dist_bin_SCRIPTS) $(srcdir)/Makefile.am \
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/ztest/Makefile.in

@@ -42,6 +42,7 @@ subdir = cmd/ztest
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

cmd/zvol_id/Makefile.in

@@ -42,6 +42,7 @@ subdir = cmd/zvol_id
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

config/kernel-automount.m4

@@ -0,0 +1,23 @@
+dnl #
+dnl # 2.6.37 API change
+dnl # The dops->d_automount() dentry operation was added as a clean
+dnl # solution to handling automounts.  Prior to this cifs/nfs clients
+dnl # which required automount support would abuse the follow_link()
+dnl # operation on directories for this purpose.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_AUTOMOUNT], [
+	AC_MSG_CHECKING([whether dops->d_automount() exists])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/dcache.h>
+	],[
+		struct vfsmount *(*d_automount) (struct path *) = NULL;
+		struct dentry_operations dops __attribute__ ((unused)) = {
+			.d_automount = d_automount,
+		};
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_AUTOMOUNT, 1, [dops->automount() exists])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])

config/kernel.m4

@@ -34,6 +34,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_XATTR_HANDLER_SET
 	ZFS_AC_KERNEL_FSYNC
 	ZFS_AC_KERNEL_EVICT_INODE
+	ZFS_AC_KERNEL_AUTOMOUNT
 	ZFS_AC_KERNEL_INSERT_INODE_LOCKED
 	ZFS_AC_KERNEL_D_OBTAIN_ALIAS
 	ZFS_AC_KERNEL_CHECK_DISK_SIZE_CHANGE

configure

@@ -14715,6 +14715,74 @@ fi
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether dops->d_automount() exists" >&5
+$as_echo_n "checking whether dops->d_automount() exists... " >&6; }
+
+
+cat confdefs.h - <<_ACEOF >conftest.c
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+
+		#include <linux/dcache.h>
+
+int
+main (void)
+{
+
+		struct vfsmount *(*d_automount) (struct path *) = NULL;
+		struct dentry_operations dops __attribute__ ((unused)) = {
+			.d_automount = d_automount,
+		};
+
+  ;
+  return 0;
+}
+
+_ACEOF
+
+
+	rm -Rf build && mkdir -p build
+	echo "obj-m := conftest.o" >build/Makefile
+	if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_AUTOMOUNT 1
+_ACEOF
+
+
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+
+
+fi
+
+	rm -Rf build
+
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether symbol insert_inode_locked is exported" >&5
 $as_echo_n "checking whether symbol insert_inode_locked is exported... " >&6; }
 	grep -q -E '[[:space:]]insert_inode_locked[[:space:]]' \
@@ -19485,6 +19553,74 @@ fi
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether dops->d_automount() exists" >&5
+$as_echo_n "checking whether dops->d_automount() exists... " >&6; }
+
+
+cat confdefs.h - <<_ACEOF >conftest.c
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+
+		#include <linux/dcache.h>
+
+int
+main (void)
+{
+
+		struct vfsmount *(*d_automount) (struct path *) = NULL;
+		struct dentry_operations dops __attribute__ ((unused)) = {
+			.d_automount = d_automount,
+		};
+
+  ;
+  return 0;
+}
+
+_ACEOF
+
+
+	rm -Rf build && mkdir -p build
+	echo "obj-m := conftest.o" >build/Makefile
+	if { ac_try='cp conftest.c build && make modules -C $LINUX_OBJ EXTRA_CFLAGS="-Werror-implicit-function-declaration $EXTRA_KCFLAGS" $ARCH_UM M=$PWD/build'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } >/dev/null && { ac_try='test -s build/conftest.o'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_AUTOMOUNT 1
+_ACEOF
+
+
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+		{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+
+
+fi
+
+	rm -Rf build
+
+
+
+
 	{ $as_echo "$as_me:$LINENO: checking whether symbol insert_inode_locked is exported" >&5
 $as_echo_n "checking whether symbol insert_inode_locked is exported... " >&6; }
 	grep -q -E '[[:space:]]insert_inode_locked[[:space:]]' \

dracut/90zfs/Makefile.in

@@ -40,6 +40,7 @@ DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

dracut/Makefile.in

@@ -39,6 +39,7 @@ DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

etc/Makefile.in

@@ -39,6 +39,7 @@ DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

etc/init.d/Makefile.in

@@ -40,6 +40,7 @@ DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

etc/zfs/Makefile.in

@@ -40,6 +40,7 @@ DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

include/Makefile.in

@@ -41,6 +41,7 @@ DIST_COMMON = $(am__kernel_HEADERS_DIST) $(am__libzfs_HEADERS_DIST) \
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

include/linux/Makefile.in

@@ -41,6 +41,7 @@ DIST_COMMON = $(am__kernel_HEADERS_DIST) $(libzfs_HEADERS) \
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \

include/linux/dcache_compat.h

@@ -29,5 +29,6 @@
 #include <linux/dcache.h>
 
 #define dname(dentry)	((char *)((dentry)->d_name.name))
+#define dlen(dentry)	((int)((dentry)->d_name.len))
 
 #endif /* _ZFS_DCACHE_H */

include/sys/Makefile.am

@@ -55,6 +55,7 @@ COMMON_H = \
 	$(top_srcdir)/include/sys/zap_leaf.h \
 	$(top_srcdir)/include/sys/zfs_acl.h \
 	$(top_srcdir)/include/sys/zfs_context.h \
+	$(top_srcdir)/include/sys/zfs_ctldir.h \
 	$(top_srcdir)/include/sys/zfs_debug.h \
 	$(top_srcdir)/include/sys/zfs_dir.h \
 	$(top_srcdir)/include/sys/zfs_fuid.h \

include/sys/Makefile.in

@@ -41,6 +41,7 @@ DIST_COMMON = $(am__kernel_HEADERS_DIST) $(am__libzfs_HEADERS_DIST) \
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps =  \
 	$(top_srcdir)/config/always-no-unused-but-set-variable.m4 \
+	$(top_srcdir)/config/kernel-automount.m4 \
 	$(top_srcdir)/config/kernel-bdev-block-device-operations.m4 \
 	$(top_srcdir)/config/kernel-bdev-logical-size.m4 \
 	$(top_srcdir)/config/kernel-bdi-setup-and-register.m4 \
@@ -159,6 +160,7 @@ am__kernel_HEADERS_DIST = $(top_srcdir)/include/sys/arc.h \
 	$(top_srcdir)/include/sys/zap_leaf.h \
 	$(top_srcdir)/include/sys/zfs_acl.h \
 	$(top_srcdir)/include/sys/zfs_context.h \
+	$(top_srcdir)/include/sys/zfs_ctldir.h \
 	$(top_srcdir)/include/sys/zfs_debug.h \
 	$(top_srcdir)/include/sys/zfs_dir.h \
 	$(top_srcdir)/include/sys/zfs_fuid.h \
@@ -255,6 +257,7 @@ am__libzfs_HEADERS_DIST = $(top_srcdir)/include/sys/arc.h \
 	$(top_srcdir)/include/sys/zap_leaf.h \
 	$(top_srcdir)/include/sys/zfs_acl.h \
 	$(top_srcdir)/include/sys/zfs_context.h \
+	$(top_srcdir)/include/sys/zfs_ctldir.h \
 	$(top_srcdir)/include/sys/zfs_debug.h \
 	$(top_srcdir)/include/sys/zfs_dir.h \
 	$(top_srcdir)/include/sys/zfs_fuid.h \
@@ -532,6 +535,7 @@ COMMON_H = \
 	$(top_srcdir)/include/sys/zap_leaf.h \
 	$(top_srcdir)/include/sys/zfs_acl.h \
 	$(top_srcdir)/include/sys/zfs_context.h \
+	$(top_srcdir)/include/sys/zfs_ctldir.h \
 	$(top_srcdir)/include/sys/zfs_debug.h \
 	$(top_srcdir)/include/sys/zfs_dir.h \
 	$(top_srcdir)/include/sys/zfs_fuid.h \

include/sys/dmu.h

@@ -643,6 +643,7 @@ extern uint64_t dmu_objset_syncprop(objset_t *os);
 extern uint64_t dmu_objset_logbias(objset_t *os);
 extern int dmu_snapshot_list_next(objset_t *os, int namelen, char *name,
     uint64_t *id, uint64_t *offp, boolean_t *case_conflict);
+extern int dmu_snapshot_id(objset_t *os, const char *snapname, uint64_t *idp);
 extern int dmu_snapshot_realname(objset_t *os, char *name, char *real,
     int maxlen, boolean_t *conflict);
 extern int dmu_dir_list_next(objset_t *os, int namelen, char *name,