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, 3 insertions, 18 deletions

diff --git a/include/sys/zfs_vfsops.h b/include/sys/zfs_vfsops.h
index 7b70f32ea..33ecf72fb 100644
--- a/include/sys/zfs_vfsops.h
+++ b/include/sys/zfs_vfsops.h
@@ -71,6 +71,8 @@ typedef struct zfs_sb {
 	uint64_t	z_nr_znodes;	/* number of znodes in the fs */
 	kmutex_t	z_znodes_lock;	/* lock for z_all_znodes */
 	struct inode	*z_ctldir;	/* .zfs directory inode */
+	avl_tree_t	z_ctldir_snaps;	/* .zfs/snapshot entries */
+	kmutex_t	z_ctldir_lock;	/* .zfs ctldir lock */
 	boolean_t	z_show_ctldir;	/* expose .zfs in the root dir */
 	boolean_t	z_issnap;	/* true if this is a snapshot */
 	boolean_t	z_vscan;	/* virus scan on/off */
@@ -93,24 +95,6 @@ typedef struct zfs_sb {
 
 #define	ZSB_XATTR	0x0001		/* Enable user xattrs */
 
-
-/*
- * Minimal snapshot helpers, the bulk of the Linux snapshot implementation
- * lives in the zpl_snap.c file which is part of the zpl source.
- */
-#define	ZFS_CTLDIR_NAME		".zfs"
-
-#define	zfs_has_ctldir(zdp)	\
-	((zdp)->z_id == ZTOZSB(zdp)->z_root && \
-	(ZTOZSB(zdp)->z_ctldir != NULL))
-#define	zfs_show_ctldir(zdp)	\
-	(zfs_has_ctldir(zdp) &&	\
-	(ZTOZSB(zdp)->z_show_ctldir))
-
-#define	ZFSCTL_INO_ROOT		0x1
-#define	ZFSCTL_INO_SNAPDIR	0x2
-#define	ZFSCTL_INO_SHARES	0x3
-
 /*
  * Allow a maximum number of links.  While ZFS does not internally limit
  * this the inode->i_nlink member is defined as an unsigned int.  To be
@@ -195,6 +179,7 @@ extern boolean_t zfs_is_readonly(zfs_sb_t *zsb);
 extern int zfs_register_callbacks(zfs_sb_t *zsb);
 extern void zfs_unregister_callbacks(zfs_sb_t *zsb);
 extern int zfs_domount(struct super_block *sb, void *data, int silent);
+extern void zfs_preumount(struct super_block *sb);
 extern int zfs_umount(struct super_block *sb);
 extern int zfs_remount(struct super_block *sb, int *flags, char *data);
 extern int zfs_root(zfs_sb_t *zsb, struct inode **ipp);