Sometimes other drivers depend on particular configfs items.  For
example, ocfs2 mounts depend on a heartbeat region item.  If that
region item is removed with rmdir(2), the ocfs2 mount must BUG or go
readonly.  Not happy.

This provides two additional API calls: configfs_depend_item() and
configfs_undepend_item().  A client driver can call
configfs_depend_item() on an existing item to tell configfs that it is
depended on.  configfs will then return -EBUSY from rmdir(2) for that
item.  When the item is no longer depended on, the client driver calls
configfs_undepend_item() on it.

These API cannot be called underneath any configfs callbacks, as
they will conflict.  They can block and allocate.  A client driver
probably shouldn't calling them of its own gumption.  Rather it should
be providing an API that external subsystems call.

How does this work?  Imagine the ocfs2 mount process.  When it mounts,
it asks for a heart region item.  This is done via a call into the
heartbeat code.  Inside the heartbeat code, the region item is looked
up.  Here, the heartbeat code calls configfs_depend_item().  If it
succeeds, then heartbeat knows the region is safe to give to ocfs2.
If it fails, it was being torn down anyway, and heartbeat can gracefully
pass up an error.

[ Fixed some bad whitespace in configfs.txt. --Mark ]
Signed-off-by: NJoel Becker <joel.becker@oracle.com>
Signed-off-by: NMark Fasheh <mark.fasheh@oracle.com>

Add a notification callback, ops->disconnect_notify(). It has the same
prototype as ->drop_item(), but it will be called just before the item
linkage is broken. This way, configfs users who want to do work while
the object is still in the heirarchy have a chance.

Client drivers will still need to config_item_put() in their
->drop_item(), if they implement it.  They need do nothing in
->disconnect_notify().  They don't have to provide it if they don't
care.  But someone who wants to be notified before ci_parent is set to
NULL can now be notified.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>
Signed-off-by: NMark Fasheh <mark.fasheh@oracle.com>

Convert the su_sem member of struct configfs_subsystem to a struct
mutex, as that's what it is. Also convert all the users and update
Documentation/configfs.txt and Documentation/configfs_example.c
accordingly.

[ Conflict in fs/dlm/config.c with commit
  3168b078 manually resolved. --Mark ]
Inspired-by: NSatyam Sharma <ssatyam@cse.iitk.ac.in>
Signed-off-by: NJoel Becker <joel.becker@oracle.com>
Signed-off-by: NMark Fasheh <mark.fasheh@oracle.com>

This patch fixes typos in various Documentation txts. The patch addresses some
+words starting with the letters 'U-Z'.

Looks like I made it through the alphabet...just in time to start over again
+too!  Maybe I can fit more profound fixes into the next round...?  Time will
+tell. :)
Signed-off-by: NMatt LaPlante <kernel1@cyberdogtech.com>
Acked-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

This patch fixes typos in various Documentation txts. The patch addresses
some words starting with the letter 'S'.
Signed-off-by: NMatt LaPlante <kernel1@cyberdogtech.com>
Acked-by: NAlan Cox <alan@redhat.com>
Acked-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

This patch fixes typos in various Documentation txts. The patch addresses
some words starting with the letters 'Q'-'R'.
Signed-off-by: NMatt LaPlante <kernel1@cyberdogtech.com>
Acked-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

This patch fixes typos in various Documentation txts. This patch addresses some
words starting with the letters 'B'-'C'.  There are also a few grammar fixes
thrown in for Randy. ;)
Signed-off-by: NMatt LaPlante <kernel1@cyberdogtech.com>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

This patch fixes typos in various Documentation txts.
This patch addresses some words starting with the letter 'A'.
Signed-off-by: NMatt LaPlante <kernel1@cyberdogtech.com>
Acked-by: NRandy Dunlap <rdunlap@xenotime.net>
Acked-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

Configfs, a file system for userspace-driven kernel object configuration.
The OCFS2 stack makes extensive use of this for propagation of cluster
configuration information into kernel.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>