linux-kernel - [PATCH 1/2] mmu_notifiers: Restore documentation for .invalidate

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Message-Id: <3cece716fc09724793aa832e755abfc9d70a8bb3.1684892404.git-series.apopple@nvidia.com>
Date:   Wed, 24 May 2023 11:47:28 +1000
From:   Alistair Popple <apopple@...dia.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, will@...nel.org,
        catalin.marinas@....com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        robin.murphy@....com, nicolinc@...dia.com,
        linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
        jgg@...dia.com, John Hubbard <jhubbard@...dia.com>,
        zhi.wang.linux@...il.com, Sean Christopherson <seanjc@...gle.com>,
        Alistair Popple <apopple@...dia.com>
Subject: [PATCH 1/2] mmu_notifiers: Restore documentation for .invalidate_range()

The .invalidate_range() callback is called by
mmu_notifier_invalidate_range() which is often called while holding
the ptl spin-lock. Therefore any implementations of this callback must
not sleep. This was originally documented when the call back was added
in commit 0f0a327fa12c ("mmu_notifier: add the callback for
mmu_notifier_invalidate_range()") but appears to have been
inadvertently removed by commit 5ff7091f5a2c ("mm, mmu_notifier:
annotate mmu notifiers with blockable invalidate callbacks").

Restore the comment to make it clear that .invalidate_range()
callbacks may not sleep.

Signed-off-by: Alistair Popple <apopple@...dia.com>
---
 include/linux/mmu_notifier.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 64a3e05..447d757 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -200,6 +200,9 @@ struct mmu_notifier_ops {
 	 * external TLB range needs to be flushed. For more in depth
 	 * discussion on this see Documentation/mm/mmu_notifier.rst
 	 *
+	 * The invalidate_range() function is called under the ptl
+	 * spin-lock and not allowed to sleep.
+	 *
 	 * Note that this function might be called with just a sub-range
 	 * of what was passed to invalidate_range_start()/end(), if
 	 * called between those functions.

base-commit: 44c026a73be8038f03dbdeef028b642880cf1511
-- 
git-series 0.9.1