linux-kernel - [PATCH] percpu_counter: unbreak __percpu_counter

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Message-ID: <alpine.LSU.2.11.1401161521340.1084@eggly.anvils>
Date:	Thu, 16 Jan 2014 15:26:48 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ming Lei <tom.leiming@...il.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Shaohua Li <shli@...ionio.com>, Jens Axboe <axboe@...nel.dk>,
	Fan Du <fan.du@...driver.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] 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@...gle.com>
---

 lib/percpu_counter.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 3.13-rc8+/lib/percpu_counter.c	2014-01-15 09:53:27.768111792 -0800
+++ linux/lib/percpu_counter.c	2014-01-16 14:58:54.156555308 -0800
@@ -82,7 +82,7 @@ void __percpu_counter_add(struct percpu_
 		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);
--
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