From fb4f88dcabdc716c7c350e09cf4a38a419b007e1 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hugh@veritas.com>
Date: Sat, 3 Sep 2005 15:54:37 -0700
Subject: [PATCH] [PATCH] swap: get_swap_page drop swap_list_lock

Rewrite get_swap_page to allocate in just the same sequence as before, but
without holding swap_list_lock across its scan_swap_map.  Decrement
nr_swap_pages and update swap_list.next in advance, while still holding
swap_list_lock.  Skip full devices by testing highest_bit.  Swapoff hold
swap_device_lock as well as swap_list_lock to clear SWP_WRITEOK.  Reduces lock
contention when there are parallel swap devices of the same priority.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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