swap_info: change to array of pointers
authorHugh Dickins <hugh.dickins@tiscali.co.uk>
Tue, 15 Dec 2009 01:58:41 +0000 (17:58 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 15 Dec 2009 16:53:15 +0000 (08:53 -0800)
commitefa90a981bbc891efad96db2a75b5487e00852ca
treefc64a5d5b71e84eb1eec2810fb0568a79a361827
parentf29ad6a99b596b8169744d107bf088e8be9e8d0d
swap_info: change to array of pointers

The swap_info_struct is only 76 or 104 bytes, but it does seem wrong
to reserve an array of about 30 of them in bss, when most people will
want only one.  Change swap_info[] to an array of pointers.

That does need a "type" field in the structure: pack it as a char with
next type and short prio (aha, char is unsigned by default on PowerPC).
Use the (admittedly peculiar) name "type" throughout for this index.

/proc/swaps does not take swap_lock: I wouldn't want it to, but do take
care with barriers when adding a new item to the array (never removed).

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/swap.h
mm/swapfile.c