The original goal of commonizing these funcs is to benefit defraging/extent_moving
codes in the future,  based on the fact that reflink and defragmentation having
the same Copy-On-Wrtie mechanism.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>

Thanks for the comments. I have incorportated them all.

CONFIG_OCFS2_FS_STATS is enabled and CONFIG_DEBUG_LOCK_ALLOC is disabled.
Statistics now look like -
ocfs2_write_ctxt: 2144 - 2136 = 8
ocfs2_inode_info: 1960 - 1848 = 112
ocfs2_journal: 168 - 160 = 8
ocfs2_lock_res: 336 - 304 = 32
ocfs2_refcount_tree: 512 - 472 = 40

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.de>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

Add a new parameter 'struct file *' to ocfs2_refcount_cow
so that we can add readahead support later.

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

Truncate is just a special case of punching holes(from new i_size to
end), we therefore could take advantage of the existing
ocfs2_remove_btree_range() to reduce the comlexity and redundancy in
alloc.c.  The goal here is to make truncate more generic and
straightforward.

Several functions only used by ocfs2_commit_truncate() will smiply be
removed.

ocfs2_remove_btree_range() was originally used by the hole punching
code, which didn't take refcount trees into account (definitely a bug).
We therefore need to change that func a bit to handle refcount trees.
It must take the refcount lock, calculate and reserve blocks for
refcount tree changes, and decrease refcounts at the end.  We replace 
ocfs2_lock_allocators() here by adding a new func
ocfs2_reserve_blocks_for_rec_trunc() which accepts some extra blocks to
reserve.  This will not hurt any other code using
ocfs2_remove_btree_range() (such as dir truncate and hole punching).

I merged the following steps into one patch since they may be
logically doing one thing, though I know it looks a little bit fat
to review.

1). Remove redundant code used by ocfs2_commit_truncate(), since we're
    moving to ocfs2_remove_btree_range anyway.

2). Add a new func ocfs2_reserve_blocks_for_rec_trunc() for purpose of
    accepting some extra blocks to reserve.

3). Change ocfs2_prepare_refcount_change_for_del() a bit to fit our
    needs.  It's safe to do this since it's only being called by
    truncate.

4). Change ocfs2_remove_btree_range() a bit to take refcount case into
    account.

5). Finally, we change ocfs2_commit_truncate() to call
    ocfs2_remove_btree_range() in a proper way.

The patch has been tested normally for sanity check, stress tests
with heavier workload will be expected.

Based on this patch, fixing the punching holes bug will be fairly easy.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
Acked-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

The ioctl will take 3 parameters: old_path, new_path and
preserve and call vfs_reflink. It is useful when we backport
reflink features to old kernels.

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

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

Now with xattr refcount support, we need to check whether
we have xattr refcounted before we remove the refcount tree.

Now the mechanism is:
1) Check whether i_clusters == 0, if no, exit.
2) check whether we have i_xattr_loc in dinode. if yes, exit.
2) Check whether we have inline xattr stored outside, if yes, exit.
4) Remove the tree.

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

In ocfs2, when xattr's value is larger than OCFS2_XATTR_INLINE_SIZE,
it will be kept outside of the blocks we store xattr entry. And they
are stored in a b-tree also. So this patch try to attach all these
clusters to refcount tree also.

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

In order to make 2 transcation(xattr and cow) independent with each other,
we CoW the whole xattr out in case we are setting them.

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