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Subject[PATCH v3 hmm 01/11] mm/mmu_notifiers: hoist do_mmu_notifier_register down_write to the caller
Date
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(-)

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)
--
2.22.0
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