[patch -mm] mm, mmu_notifier: annotate mmu notifiers with blockable invalidate callbacks fix fix

From: David Rientjes <rientjes@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Michal Hocko" <mhocko@suse.com>,
	"Andrea Arcangeli" <aarcange@redhat.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Paul Mackerras" <paulus@samba.org>,
	"Oded Gabbay" <oded.gabbay@gmail.com>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Christian König" <christian.koenig@amd.com>,
	"David Airlie" <airlied@linux.ie>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Doug Ledford" <dledford@redhat.com>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Mike Marciniszyn" <mike.marciniszyn@intel.com>,
	"Sean Hefty" <sean.hefty@intel.com>,
	"Dimitri Sivanich" <sivanich@sgi.com>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [patch -mm] mm, mmu_notifier: annotate mmu notifiers with blockable invalidate callbacks fix fix
Date: Tue, 9 Jan 2018 13:40:21 -0800 (PST)	[thread overview]
Message-ID: <alpine.DEB.2.10.1801091339570.240101@chino.kir.corp.google.com> (raw)
In-Reply-To: <20171215150429.f68862867392337f35a49848@linux-foundation.org>

Fix mmu_notifier.h comments in "mm, mmu_notifier: annotate mmu notifiers
with blockable invalidate callbacks".

mmu_notifier_invalidate_range_end() can also call the invalidate_range()
callback, so it must not block for MMU_INVALIDATE_DOES_NOT_BLOCK to be
set.

Also remove a bogus comment about invalidate_range() always being called
under the ptl spinlock.

Signed-off-by: David Rientjes <rientjes@google.com>
---
 include/linux/mmu_notifier.h | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -34,8 +34,8 @@ struct mmu_notifier_ops {
 	 * Flags to specify behavior of callbacks for this MMU notifier.
 	 * Used to determine which context an operation may be called.
 	 *
-	 * MMU_INVALIDATE_DOES_NOT_BLOCK: invalidate_{start,end} does not
-	 *				  block
+	 * MMU_INVALIDATE_DOES_NOT_BLOCK: invalidate_range_* callbacks do not
+	 *	block
 	 */
 	int flags;
 
@@ -151,8 +151,9 @@ struct mmu_notifier_ops {
 	 * address space but may still be referenced by sptes until
 	 * the last refcount is dropped.
 	 *
-	 * If both of these callbacks cannot block, mmu_notifier_ops.flags
-	 * should have MMU_INVALIDATE_DOES_NOT_BLOCK set.
+	 * If both of these callbacks cannot block, and invalidate_range
+	 * cannot block, mmu_notifier_ops.flags should have
+	 * MMU_INVALIDATE_DOES_NOT_BLOCK set.
 	 */
 	void (*invalidate_range_start)(struct mmu_notifier *mn,
 				       struct mm_struct *mm,
@@ -175,12 +176,13 @@ struct mmu_notifier_ops {
 	 * external TLB range needs to be flushed. For more in depth
 	 * discussion on this see Documentation/vm/mmu_notifier.txt
 	 *
-	 * 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.
+	 *
+	 * If this callback cannot block, and invalidate_range_{start,end}
+	 * cannot block, mmu_notifier_ops.flags should have
+	 * MMU_INVALIDATE_DOES_NOT_BLOCK set.
 	 */
 	void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm,
 				 unsigned long start, unsigned long end);
