Add .zfs control directory

Add support for the .zfs control directory.  This was accomplished
by leveraging as much of the existing ZFS infrastructure as posible
and updating it for Linux as required.  The bulk of the core
functionality is now all there with the following limitations.

*) 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.

*) Creating/destroying/renaming snapshots with mkdir/rmdir/mv
   in the .zfs/snapshot directory works as expected.  However,
   this functionality is only available to root until zfs
   delegations are finished.

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

The following issues are known defeciences, but we expect them to
be addressed by future commits.

*) Add automount support for kernels older the 2.6.37.  This should
   be possible using follow_link() which is what Linux did before.

*) Accessing the .zfs/snapshot directory via NFS is not yet possible.
   The majority of the ground work for this is complete.  However,
   finishing this work will require resolving some lingering
   integration issues with the Linux NFS kernel server.

*) The .zfs/shares directory exists but no futher smb functionality
   has yet been implemented.

Contributions-by: Rohan Puri <[email protected]>
Contributiobs-by: Andrew Barnes <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #173

1 files changed, 37 insertions, 10 deletions

diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index fb319a547..8f1c713c0 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -56,6 +56,7 @@
 #include <sys/modctl.h>
 #include <sys/refstr.h>
 #include <sys/zfs_ioctl.h>
+#include <sys/zfs_ctldir.h>
 #include <sys/zfs_fuid.h>
 #include <sys/bootconf.h>
 #include <sys/sunddi.h>
@@ -710,6 +711,10 @@ zfs_sb_create(const char *osname, zfs_sb_t **zsbp)
 	for (i = 0; i != ZFS_OBJ_MTX_SZ; i++)
 		mutex_init(&zsb->z_hold_mtx[i], NULL, MUTEX_DEFAULT, NULL);
 
+	avl_create(&zsb->z_ctldir_snaps, snapentry_compare,
+	    sizeof (zfs_snapentry_t), offsetof(zfs_snapentry_t, se_node));
+	mutex_init(&zsb->z_ctldir_lock, NULL, MUTEX_DEFAULT, NULL);
+
 	*zsbp = zsb;
 	return (0);
 
@@ -819,6 +824,8 @@ zfs_sb_free(zfs_sb_t *zsb)
 	rw_destroy(&zsb->z_fuid_lock);
 	for (i = 0; i != ZFS_OBJ_MTX_SZ; i++)
 		mutex_destroy(&zsb->z_hold_mtx[i]);
+	mutex_destroy(&zsb->z_ctldir_lock);
+	avl_destroy(&zsb->z_ctldir_snaps);
 	kmem_free(zsb, sizeof (zfs_sb_t));
 }
 EXPORT_SYMBOL(zfs_sb_free);
@@ -1183,9 +1190,6 @@ zfs_domount(struct super_block *sb, void *data, int silent)
 		mutex_exit(&zsb->z_os->os_user_ptr_lock);
 	} else {
 		error = zfs_sb_setup(zsb, B_TRUE);
-#ifdef HAVE_SNAPSHOT
-		(void) zfs_snap_create(zsb);
-#endif /* HAVE_SNAPSHOT */
 	}
 
 	/* Allocate a root inode for the filesystem. */
@@ -1202,6 +1206,9 @@ zfs_domount(struct super_block *sb, void *data, int silent)
 		error = ENOMEM;
 		goto out;
 	}
+
+	if (!zsb->z_issnap)
+		zfsctl_create(zsb);
 out:
 	if (error) {
 		dmu_objset_disown(zsb->z_os, zsb);
@@ -1212,6 +1219,27 @@ out:
 }
 EXPORT_SYMBOL(zfs_domount);
 
+/*
+ * Called when an unmount is requested and certain sanity checks have
+ * already passed.  At this point no dentries or inodes have been reclaimed
+ * from their respective caches.  We drop the extra reference on the .zfs
+ * control directory to allow everything to be reclaimed.  All snapshots
+ * must already have been unmounted to reach this point.
+ */
+void
+zfs_preumount(struct super_block *sb)
+{
+	zfs_sb_t *zsb = sb->s_fs_info;
+
+	if (zsb->z_ctldir != NULL)
+		zfsctl_destroy(zsb);
+}
+EXPORT_SYMBOL(zfs_preumount);
+
+/*
+ * Called once all other unmount released tear down has occurred.
+ * It is our responsibility to release any remaining infrastructure.
+ */
 /*ARGSUSED*/
 int
 zfs_umount(struct super_block *sb)
@@ -1288,11 +1316,10 @@ zfs_vget(struct super_block *sb, struct inode **ipp, fid_t *fidp)
 
 		ZFS_EXIT(zsb);
 
-#ifdef HAVE_SNAPSHOT
-		err = zfsctl_lookup_objset(vfsp, objsetid, &zsb);
+		err = zfsctl_lookup_objset(sb, objsetid, &zsb);
 		if (err)
 			return (EINVAL);
-#endif /* HAVE_SNAPSHOT */
+
 		ZFS_ENTER(zsb);
 	}
 
@@ -1309,22 +1336,20 @@ zfs_vget(struct super_block *sb, struct inode **ipp, fid_t *fidp)
 		return (EINVAL);
 	}
 
-#ifdef HAVE_SNAPSHOT
 	/* A zero fid_gen means we are in the .zfs control directories */
 	if (fid_gen == 0 &&
 	    (object == ZFSCTL_INO_ROOT || object == ZFSCTL_INO_SNAPDIR)) {
 		*ipp = zsb->z_ctldir;
 		ASSERT(*ipp != NULL);
 		if (object == ZFSCTL_INO_SNAPDIR) {
-			VERIFY(zfsctl_root_lookup(*ipp, "snapshot", ipp, NULL,
-			    0, NULL, NULL, NULL, NULL, NULL) == 0);
+			VERIFY(zfsctl_root_lookup(*ipp, "snapshot", ipp,
+			    0, kcred, NULL, NULL) == 0);
 		} else {
 			igrab(*ipp);
 		}
 		ZFS_EXIT(zsb);
 		return (0);
 	}
-#endif /* HAVE_SNAPSHOT */
 
 	gen_mask = -1ULL >> (64 - 8 * i);
 
@@ -1550,6 +1575,7 @@ EXPORT_SYMBOL(zfs_get_zplprop);
 void
 zfs_init(void)
 {
+	zfsctl_init();
 	zfs_znode_init();
 	dmu_objset_register_type(DMU_OST_ZFS, zfs_space_delta_cb);
 	register_filesystem(&zpl_fs_type);
@@ -1561,4 +1587,5 @@ zfs_fini(void)
 {
 	unregister_filesystem(&zpl_fs_type);
 	zfs_znode_fini();
+	zfsctl_fini();
 }