Revert "mm, mmu_notifier: annotate mmu notifiers with blockable invalidate callbacks"

Revert 5ff7091f5a2ca ("mm, mmu_notifier: annotate mmu notifiers with
blockable invalidate callbacks").

MMU_INVALIDATE_DOES_NOT_BLOCK flags was the only one used and it is no
longer needed since 93065ac753e4 ("mm, oom: distinguish blockable mode for
mmu notifiers").  We now have a full support for per range !blocking
behavior so we can drop the stop gap workaround which the per notifier
flag was used for.

Link: http://lkml.kernel.org/r/20180827112623.8992-4-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/infiniband/hw/hfi1/mmu_rb.c

@@ -77,7 +77,6 @@ static void do_remove(struct mmu_rb_handler *handler,
 static void handle_remove(struct work_struct *work);
 
 static const struct mmu_notifier_ops mn_opts = {
-	.flags = MMU_INVALIDATE_DOES_NOT_BLOCK,
 	.invalidate_range_start = mmu_notifier_range_start,
 };
 

drivers/iommu/amd_iommu_v2.c

@@ -427,7 +427,6 @@ static void mn_release(struct mmu_notifier *mn, struct mm_struct *mm)
 }
 
 static const struct mmu_notifier_ops iommu_mn = {
-	.flags			= MMU_INVALIDATE_DOES_NOT_BLOCK,
 	.release		= mn_release,
 	.clear_flush_young      = mn_clear_flush_young,
 	.invalidate_range       = mn_invalidate_range,

drivers/iommu/intel-svm.c

@@ -273,7 +273,6 @@ static void intel_mm_release(struct mmu_notifier *mn, struct mm_struct *mm)
 }
 
 static const struct mmu_notifier_ops intel_mmuops = {
-	.flags = MMU_INVALIDATE_DOES_NOT_BLOCK,
 	.release = intel_mm_release,
 	.change_pte = intel_change_pte,
 	.invalidate_range = intel_invalidate_range,

drivers/misc/sgi-gru/grutlbpurge.c

@@ -261,7 +261,6 @@ static void gru_release(struct mmu_notifier *mn, struct mm_struct *mm)
 
 
 static const struct mmu_notifier_ops gru_mmuops = {
-	.flags			= MMU_INVALIDATE_DOES_NOT_BLOCK,
 	.invalidate_range_start	= gru_invalidate_range_start,
 	.invalidate_range_end	= gru_invalidate_range_end,
 	.release		= gru_release,

include/linux/mmu_notifier.h

@@ -2,7 +2,6 @@
 #ifndef _LINUX_MMU_NOTIFIER_H
 #define _LINUX_MMU_NOTIFIER_H
 
-#include <linux/types.h>
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/mm_types.h>
@@ -11,9 +10,6 @@
 struct mmu_notifier;
 struct mmu_notifier_ops;
 
-/* mmu_notifier_ops flags */
-#define MMU_INVALIDATE_DOES_NOT_BLOCK	(0x01)
-
 #ifdef CONFIG_MMU_NOTIFIER
 
 /*
@@ -30,15 +26,6 @@ struct mmu_notifier_mm {
 };
 
 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_range_* callbacks do not
-	 *	block
-	 */
-	int flags;
-
 	/*
 	 * Called either by mmu_notifier_unregister or when the mm is
 	 * being destroyed by exit_mmap, always before all pages are
@@ -183,10 +170,6 @@ struct mmu_notifier_ops {
 	 * 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);
@@ -241,7 +224,6 @@ extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 				  bool only_end);
 extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
 				  unsigned long start, unsigned long end);
-extern bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm);
 
 static inline void mmu_notifier_release(struct mm_struct *mm)
 {
@@ -495,11 +477,6 @@ static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
 {
 }
 
-static inline bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
-{
-	return false;
-}
-
 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 {
 }

mm/mmu_notifier.c

@@ -247,37 +247,6 @@ void __mmu_notifier_invalidate_range(struct mm_struct *mm,
 }
 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range);
 
-/*
- * Must be called while holding mm->mmap_sem for either read or write.
- * The result is guaranteed to be valid until mm->mmap_sem is dropped.
- */
-bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
-{
-	struct mmu_notifier *mn;
-	int id;
-	bool ret = false;
-
-	WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
-
-	if (!mm_has_notifiers(mm))
-		return ret;
-
-	id = srcu_read_lock(&srcu);
-	hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
-		if (!mn->ops->invalidate_range &&
-		    !mn->ops->invalidate_range_start &&
-		    !mn->ops->invalidate_range_end)
-				continue;
-
-		if (!(mn->ops->flags & MMU_INVALIDATE_DOES_NOT_BLOCK)) {
-			ret = true;
-			break;
-		}
-	}
-	srcu_read_unlock(&srcu, id);
-	return ret;
-}
-
 static int do_mmu_notifier_register(struct mmu_notifier *mn,
 				    struct mm_struct *mm,
 				    int take_mmap_sem)

virt/kvm/kvm_main.c

@@ -497,7 +497,6 @@ static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
 }
 
 static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
-	.flags			= MMU_INVALIDATE_DOES_NOT_BLOCK,
 	.invalidate_range_start	= kvm_mmu_notifier_invalidate_range_start,
 	.invalidate_range_end	= kvm_mmu_notifier_invalidate_range_end,
 	.clear_flush_young	= kvm_mmu_notifier_clear_flush_young,