From: Hugh Dickins <hughd@google.com>
Date: Thu, 16 Jan 2014 23:26:48 +0000 (-0800)
Subject: percpu_counter: unbreak __percpu_counter_add()
X-Git-Url: http://git.efficios.com/?p=deliverable%2Flinux.git;a=commitdiff_plain;h=d1969a84dd6a44d375aa82bba7d6c38713a429c3

percpu_counter: unbreak __percpu_counter_add()

Commit 74e72f894d56 ("lib/percpu_counter.c: fix __percpu_counter_add()")
looked very plausible, but its arithmetic was badly wrong: obvious once
you see the fix, but maddening to get there from the weird tmpfs ENOSPCs

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Shaohua Li <shli@fusionio.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Fan Du <fan.du@windriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index 1da85bb1bc07..8280a5dd1727 100644
--- a/lib/percpu_counter.c
+++ b/lib/percpu_counter.c
@@ -82,7 +82,7 @@ void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
 		unsigned long flags;
 		raw_spin_lock_irqsave(&fbc->lock, flags);
 		fbc->count += count;
-		 __this_cpu_sub(*fbc->counters, count);
+		__this_cpu_sub(*fbc->counters, count - amount);
 		raw_spin_unlock_irqrestore(&fbc->lock, flags);
 	} else {
 		this_cpu_add(*fbc->counters, amount);