mm/mmu_notifiers: hoist do_mmu_notifier_register down_write to the caller
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.
Link: https://lore.kernel.org/r/20190806231548.25242-2-jgg@ziepe.ca
Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Tested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index b567062..218a6f1 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -236,22 +236,22 @@
}
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 @@
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
@@ -302,20 +300,15 @@
*/
int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
{
- return do_mmu_notifier_register(mn, mm, 1);
+ int ret;
+
+ down_write(&mm->mmap_sem);
+ ret = __mmu_notifier_register(mn, mm);
+ up_write(&mm->mmap_sem);
+ return ret;
}
EXPORT_SYMBOL_GPL(mmu_notifier_register);
-/*
- * 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);
-}
-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)
{
