In ocfs2_extend_rotate_transaction, op_credits is the orignal
credits in the handle and we only want to extend the credits
for the rotation, but the old solution always double it. It
is harmless for some minor operations, but for actions like
reflink we may rotate tree many times and cause the credits
increase dramatically. So this patch try to only increase
the desired credits.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

During CoW, if the old extent record is refcounted, we allocate
som new clusters and do CoW. Actually we can have some improvement
here. If the old extent has refcount=1, that means now it is only
used by this file. So we don't need to allocate new clusters, just
remove the refcounted flag and it is OK. We also have to remove
it from the refcount tree while not deleting it.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

This patch try CoW support for a refcounted record.

the whole process will be:
1. Calculate how many clusters we need to CoW and where we start.
   Extents that are not completely encompassed by the write will
   be broken on 1MB boundaries.
2. Do CoW for the clusters with the help of page cache.
3. Change the b-tree structure with the new allocated clusters.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

Add 'Decrement refcount for delete' in to the normal truncate
process. So for a refcounted extent record, call refcount rec
decrementation instead of cluster free.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

Add function ocfs2_mark_extent_refcounted which can mark
an extent refcounted.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

    Given a physical cpos and length, decrement the refcount
in the tree. If the refcount for any portion of the extent goes
to zero, that portion is queued for freeing.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

Now fs/ocfs2/alloc.c has more than 7000 lines. It contains our
basic b-tree operation. Although we have already make our b-tree
operation generic, the basic structrue ocfs2_path which is used
to iterate one b-tree branch is still static and limited to only
used in alloc.c. As refcount tree need them and I don't want to
add any more b-tree unrelated code to alloc.c, export them out.

Signed-off-by: Tao Ma <tao.ma@oracle.com> 

Add refcount b-tree as a new extent tree so that it can
use the b-tree to store and maniuplate ocfs2_refcount_rec.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

ocfs2_mark_extent_written actually does the following things:
1. check the parameters.
2. initialize the left_path and split_rec.
3. call __ocfs2_mark_extent_written. it will do:
   1) check the flags of unwritten
   2) do the real split work.
The whole process is packed tightly somehow. So this patch
will abstract 2 different functions so that future b-tree
operation can work with it.

1. __ocfs2_split_extent will accept path and split_rec and do
  the real split work.
2. ocfs2_change_extent_flag will accept a new flag and initialize
   path and split_rec.

So now ocfs2_mark_extent_written will do:
1. check the parameters.
2. call ocfs2_change_extent_flag.
   1) initalize the left_path and split_rec.
   2) check whether the new flags conflict with the old one.
   3) call __ocfs2_split_extent to do the split.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

Add a new operation eo_ocfs2_extent_contig int the extent tree's
operations vector. So that with the new refcount tree, We want
this so that refcount trees can always return CONTIG_NONE and
prevent extent merging.
Signed-off-by: NTao Ma <tao.ma@oracle.com>

With this commit, extent tree operations are divorced from inodes and
rely on ocfs2_caching_info.  Phew!
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

We only allow unwritten extents on data, so the toplevel
ocfs2_mark_extent_written() can use an inode all it wants.  But the
subfunction isn't even using the inode argument.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Don't use a struct inode anymore.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

It already has an extent_tree.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

One more generic btree function that is isolated from struct inode.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

One more function that doesn't need a struct inode to pass to its
children.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

One more function down, no inode in the entire insert-extent chain.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

ocfs2_insert_extent() wants to insert a record into the extent map if
it's an inode data extent.  But since many btrees can call that
function, let's make it an op on ocfs2_extent_tree.  Other tree types
can leave it empty.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

It's not using it, so remove it from the parameter list.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

It already has an ocfs2_extent_tree and doesn't need the inode.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

We don't want struct inode in generic btree operations.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Don't pass the inode in.  We don't want it around for generic btree
operations.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

They aren't using it, so remove it from their parameter lists.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Another on the way to generic btree functions.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Give it an ocfs2_extent_tree and it is happy.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

ocfs2_remove_extent() wants to truncate the extent map if it's
truncating an inode data extent.  But since many btrees can call that
function, let's make it an op on ocfs2_extent_tree.  Other tree types
can leave it empty.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

It's not using it anymore.  Remove it from the parameter list.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

ocfs2_grow_branch() not really using it other than to pass it to the
subfunctions ocfs2_shift_tree_depth(), ocfs2_find_branch_target(), and
ocfs2_add_branch().  The first two weren't it either, so they drop the
argument.  ocfs2_add_branch() only passed it to
ocfs2_adjust_rightmost_branch(), which drops the inode argument and uses
the ocfs2_extent_tree as well.

ocfs2_append_rec_to_path() can be take an ocfs2_extent_tree instead of
the inode.  The function ocfs2_adjust_rightmost_records() goes along for
the ride.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

It's not using it, so remove it from the parameter list.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Drop it from the parameters - they already have ocfs2_extent_list.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

It already gets ocfs2_extent_tree, so we can just use that.  This chains
to the same modification for ocfs2_remove_rightmost_path() and
ocfs2_rotate_rightmost_leaf_left().
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

It already has struct ocfs2_extent_tree, which has the caching info.  So
we don't need to pass it struct inode.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

It already has struct ocfs2_extent_tree, which has the caching info.  So
we don't need to pass it struct inode.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Pass in the extent tree, which is all we need.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

We don't need struct inode in ocfs2_rotate_tree_right() anymore.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

We can get to the inode from the caching information.  Other parent
types don't need it.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Get rid of the inode argument.  Use extent_tree instead.  This means a
few more functions have to pass an extent_tree around.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Pass the ocfs2_extent_list down through ocfs2_rotate_tree_right() and
get rid of struct inode in ocfs2_rotate_subtree_root_right().
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

Completely unused argument.  Get rid of it.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>

ocfs2_unlink_path() doesn't need struct inode, so let's pass it struct
ocfs2_extent_tree.
Signed-off-by: NJoel Becker <joel.becker@oracle.com>