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 1da85bb1bc07ad3289b698776ed174b0f901e17c..8280a5dd172780371711743d297fcd0fd4e4360a 100644 (file)
--- 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);