[v3,hmm,01/11] mm/mmu_notifiers: hoist do_mmu_notifier_register down_write to the caller
diff mbox series

Message ID 20190806231548.25242-2-jgg@ziepe.ca
State Accepted
Delegated to: Jason Gunthorpe
Headers show
Series
  • Add mmu_notifier_get/put for managing mmu notifier registrations
Related show

Commit Message

Jason Gunthorpe Aug. 6, 2019, 11:15 p.m. UTC
From: Jason Gunthorpe <jgg@mellanox.com>

This simplifies the code to not have so many one line functions and extra
logic. __mmu_notifier_register() simply becomes the entry point to
register the notifier, and the other one calls it under lock.

Also add a lockdep_assert to check that the callers are holding the lock
as expected.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
---
 mm/mmu_notifier.c | 35 ++++++++++++++---------------------
 1 file changed, 14 insertions(+), 21 deletions(-)

Comments

Christoph Hellwig Aug. 8, 2019, 10:24 a.m. UTC | #1
On Tue, Aug 06, 2019 at 08:15:38PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@mellanox.com>
> 
> This simplifies the code to not have so many one line functions and extra
> logic. __mmu_notifier_register() simply becomes the entry point to
> register the notifier, and the other one calls it under lock.
> 
> Also add a lockdep_assert to check that the callers are holding the lock
> as expected.
> 
> Suggested-by: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
Ralph Campbell Aug. 14, 2019, 8:14 p.m. UTC | #2
On 8/6/19 4:15 PM, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@mellanox.com>
> 
> This simplifies the code to not have so many one line functions and extra
> logic. __mmu_notifier_register() simply becomes the entry point to
> register the notifier, and the other one calls it under lock.
> 
> Also add a lockdep_assert to check that the callers are holding the lock
> as expected.
> 
> Suggested-by: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

Nice clean up.
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>

Patch
diff mbox series

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index b5670620aea0fc..218a6f108bc2d0 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -236,22 +236,22 @@  void __mmu_notifier_invalidate_range(struct mm_struct *mm,
 }
 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range);
 
-static int do_mmu_notifier_register(struct mmu_notifier *mn,
-				    struct mm_struct *mm,
-				    int take_mmap_sem)
+/*
+ * Same as mmu_notifier_register but here the caller must hold the
+ * mmap_sem in write mode.
+ */
+int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
 {
 	struct mmu_notifier_mm *mmu_notifier_mm;
 	int ret;
 
+	lockdep_assert_held_write(&mm->mmap_sem);
 	BUG_ON(atomic_read(&mm->mm_users) <= 0);
 
-	ret = -ENOMEM;
 	mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
 	if (unlikely(!mmu_notifier_mm))
-		goto out;
+		return -ENOMEM;
 
-	if (take_mmap_sem)
-		down_write(&mm->mmap_sem);
 	ret = mm_take_all_locks(mm);
 	if (unlikely(ret))
 		goto out_clean;
@@ -279,13 +279,11 @@  static int do_mmu_notifier_register(struct mmu_notifier *mn,
 
 	mm_drop_all_locks(mm);
 out_clean:
-	if (take_mmap_sem)
-		up_write(&mm->mmap_sem);
 	kfree(mmu_notifier_mm);
-out:
 	BUG_ON(atomic_read(&mm->mm_users) <= 0);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(__mmu_notifier_register);
 
 /*
  * Must not hold mmap_sem nor any other VM related lock when calling
@@ -302,19 +300,14 @@  static int do_mmu_notifier_register(struct mmu_notifier *mn,
  */
 int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
 {
-	return do_mmu_notifier_register(mn, mm, 1);
-}
-EXPORT_SYMBOL_GPL(mmu_notifier_register);
+	int ret;
 
-/*
- * Same as mmu_notifier_register but here the caller must hold the
- * mmap_sem in write mode.
- */
-int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
-{
-	return do_mmu_notifier_register(mn, mm, 0);
+	down_write(&mm->mmap_sem);
+	ret = __mmu_notifier_register(mn, mm);
+	up_write(&mm->mmap_sem);
+	return ret;
 }
-EXPORT_SYMBOL_GPL(__mmu_notifier_register);
+EXPORT_SYMBOL_GPL(mmu_notifier_register);
 
 /* this is called after the last mmu_notifier_unregister() returned */
 void __mmu_notifier_mm_destroy(struct mm_struct *mm)