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From:   "Joel Fernandes (Google)" <joel@joelfernandes.org>
To:     linux-kernel@vger.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        surenb@google.com,
        =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= <arve@android.com>,
        Christian Brauner <christian@brauner.io>,
        devel@driverdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Martijn Coenen <maco@android.com>,
        Todd Kjos <tkjos@android.com>
Subject: [RFC] ashmem: Fix ashmem shrinker nr_to_scan
Date:   Thu,  5 Mar 2020 20:19:30 -0500
Message-Id: <20200306011930.99378-1-joel@joelfernandes.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

nr_to_scan is the number of pages to be freed however ashmem doesn't
discount nr_to_scan correctly as it frees ranges. It should be
discounting them by pages than by ranges. Correct the issue.

Cc: surenb@google.com
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 drivers/staging/android/ashmem.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
index 5891d0744a760..cb525ea6db98a 100644
--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -458,6 +458,8 @@ ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 		lru_del(range);
 
 		freed += range_size(range);
+		sc->nr_to_scan -=  range_size(range);
+
 		mutex_unlock(&ashmem_mutex);
 		f->f_op->fallocate(f,
 				   FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
@@ -467,7 +469,7 @@ ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 			wake_up_all(&ashmem_shrink_wait);
 		if (!mutex_trylock(&ashmem_mutex))
 			goto out;
-		if (--sc->nr_to_scan <= 0)
+		if (sc->nr_to_scan <= 0)
 			break;
 	}
 	mutex_unlock(&ashmem_mutex);
-- 
2.25.0.265.gbab2e86ba0-goog