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From:   Michal Hocko <mhocko@kernel.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        Michal Hocko <mhocko@suse.com>,
        Jerome Glisse <jglisse@redhat.com>
Subject: [PATCH 2/3] mm, mmu_notifier: be explicit about range invalition non-blocking mode
Date:   Mon, 27 Aug 2018 13:26:22 +0200
Message-Id: <20180827112623.8992-3-mhocko@kernel.org>
In-Reply-To: <20180827112623.8992-1-mhocko@kernel.org>
References: <20180827112623.8992-1-mhocko@kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Michal Hocko <mhocko@suse.com>

If invalidate_range_start is called for !blocking mode then all
callbacks have to guarantee they will no block/sleep. The same obviously
applies to invalidate_range_end because this operation pairs with the
former and they are called from the same context. Make sure this is
appropriately documented.

Cc: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 include/linux/mmu_notifier.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 133ba78820ee..698e371aafe3 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -153,7 +153,9 @@ struct mmu_notifier_ops {
 	 *
 	 * If blockable argument is set to false then the callback cannot
 	 * sleep and has to return with -EAGAIN. 0 should be returned
-	 * otherwise.
+	 * otherwise. Please note that if invalidate_range_start approves
+	 * a non-blocking behavior then the same applies to
+	 * invalidate_range_end.
 	 *
 	 */
 	int (*invalidate_range_start)(struct mmu_notifier *mn,
-- 
2.18.0