From: Hugh Dickins <hughd@google.com>
Date: Wed, 20 Feb 2013 02:14:40 +0000 (+1100)
Subject: swap: add per-partition lock for swapfile fix
X-Git-Tag: next-20130220~1^2~460
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=728cff79227f1315a9e224230d4b7c53fafa0162;p=karo-tx-linux.git

swap: add per-partition lock for swapfile fix

I had all cpus spinning in swap_info_get(), for the lock on an area
being swapped off: probably because get_swap_page() forgot to unlock.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/swapfile.c b/mm/swapfile.c
index dfaff5f92865..7df5270fe3c8 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -470,10 +470,9 @@ swp_entry_t get_swap_page(void)
 		spin_unlock(&swap_lock);
 		/* This is called for allocating swap entry for cache */
 		offset = scan_swap_map(si, SWAP_HAS_CACHE);
-		if (offset) {
-			spin_unlock(&si->lock);
+		spin_unlock(&si->lock);
+		if (offset)
 			return swp_entry(type, offset);
-		}
 		spin_lock(&swap_lock);
 		next = swap_list.next;
 	}