tree b0938ea773953f869b22101bb021e5710d0a0fec
parent e33ac8bdb0c84fe7afd2c45537b763faf28c589e
author Tejun Heo <htejun@gmail.com> 1181760313 +0900
committer Greg Kroah-Hartman <gregkh@suse.de> 1184195343 -0700

ida: implement idr based id allocator

Implement idr based id allocator.  ida is used the same way idr is
used but lacks id -> ptr translation and thus consumes much less
memory.  struct ida_bitmap is attached as leaf nodes to idr tree which
is managed by the idr code.  Each ida_bitmap is 128bytes long and
contains slightly less than a thousand slots.

ida is more aggressive with releasing extra resources acquired using
ida_pre_get().  After every successful id allocation, ida frees one
reserved idr_layer if possible.  Reserved ida_bitmap is not freed
automatically but only one ida_bitmap is reserved and it's almost
always used right away.  Under most circumstances, ida won't hold on
to memory for too long which isn't actively used.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>