xfs: prepare xfs_btree_cur for dynamic cursor heights
Source kernel commit:
6ca444cfd663545e9e1c19ad2695836ffafad0a6
Split out the btree level information into a separate struct and put it
at the end of the cursor structure as a VLA. Files with huge data forks
(and in the future, the realtime rmap btree) will require the ability to
support many more levels than a per-AG btree cursor, which means that
we're going to create per-btree type cursor caches to conserve memory
for the more common case.
Note that a subsequent patch actually introduces dynamic cursor heights.
This one merely rearranges the structure to prepare for that.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>