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

[David Rientjes]

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@xxxxxxxxxx>
---
 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);