maple_tree: introduce mas_prev_slot() interface

Sometimes the user needs to revert to the previous slot, regardless of if
it is empty or not.  Add an interface to go to the previous slot.

Since there can't be two consecutive NULLs in the tree, the mas_prev()
function can be implemented by calling mas_prev_slot() a maximum of 2
times.  Change the underlying interface to use mas_prev_slot() to align
the code.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Liam R. Howlett <[email protected]>
Cc: David Binderman <[email protected]>
Cc: Peng Zhang <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Vernon Yang <[email protected]>
Cc: Wei Yang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions