simplify follow_pte a bit

simplify follow_pte a bit

[Christoph Hellwig]

Hi Andrew,

this small series drops the not needed follow_pte_pmd exports, and
simplifies the follow_pte family of functions a bit.

[PATCH 1/2] mm: unexport follow_pte_pmd

[Christoph Hellwig]

follow_pte_pmd is only used by the DAX code, which can't be modular.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/memory.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index c48f8df6e50268..00458e7b49fef8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4787,7 +4787,6 @@ int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 						    ptepp, pmdpp, ptlp)));
 	return res;
 }
-EXPORT_SYMBOL(follow_pte_pmd);
 
 /**
  * follow_pfn - look up PFN at a user virtual address
-- 
2.28.0

[PATCH 2/2] mm: simplify follow_pte{,pmd}

[Christoph Hellwig]

Merge __follow_pte_pmd, follow_pte_pmd and follow_pte into a single
follow_pte function and just pass two additional NULL arguments for
the two previous follow_pte callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/dax.c           |  9 ++++-----
 include/linux/mm.h |  6 +++---
 mm/memory.c        | 35 +++++------------------------------
 3 files changed, 12 insertions(+), 38 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 5b47834f2e1bb5..26d5dcd2d69e5c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -810,12 +810,11 @@ static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
 		address = pgoff_address(index, vma);
 
 		/*
-		 * Note because we provide range to follow_pte_pmd it will
-		 * call mmu_notifier_invalidate_range_start() on our behalf
-		 * before taking any lock.
+		 * Note because we provide range to follow_pte it will call
+		 * mmu_notifier_invalidate_range_start() on our behalf before
+		 * taking any lock.
 		 */
-		if (follow_pte_pmd(vma->vm_mm, address, &range,
-				   &ptep, &pmdp, &ptl))
+		if (follow_pte(vma->vm_mm, address, &range, &ptep, &pmdp, &ptl))
 			continue;
 
 		/*
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ef360fe70aafcf..113b0b4fd90af5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1655,9 +1655,9 @@ void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
 		unsigned long end, unsigned long floor, unsigned long ceiling);
 int
 copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma);
-int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
-		   struct mmu_notifier_range *range,
-		   pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp);
+int follow_pte(struct mm_struct *mm, unsigned long address,
+		struct mmu_notifier_range *range, pte_t **ptepp, pmd_t **pmdpp,
+		spinlock_t **ptlp);
 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
 	unsigned long *pfn);
 int follow_phys(struct vm_area_struct *vma, unsigned long address,
diff --git a/mm/memory.c b/mm/memory.c
index 00458e7b49fef8..fa00682f7a4312 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4696,9 +4696,9 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
 }
 #endif /* __PAGETABLE_PMD_FOLDED */
 
-static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
-			    struct mmu_notifier_range *range,
-			    pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
+int follow_pte(struct mm_struct *mm, unsigned long address,
+	       struct mmu_notifier_range *range, pte_t **ptepp, pmd_t **pmdpp,
+	       spinlock_t **ptlp)
 {
 	pgd_t *pgd;
 	p4d_t *p4d;
@@ -4763,31 +4763,6 @@ static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 	return -EINVAL;
 }
 
-static inline int follow_pte(struct mm_struct *mm, unsigned long address,
-			     pte_t **ptepp, spinlock_t **ptlp)
-{
-	int res;
-
-	/* (void) is needed to make gcc happy */
-	(void) __cond_lock(*ptlp,
-			   !(res = __follow_pte_pmd(mm, address, NULL,
-						    ptepp, NULL, ptlp)));
-	return res;
-}
-
-int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
-		   struct mmu_notifier_range *range,
-		   pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
-{
-	int res;
-
-	/* (void) is needed to make gcc happy */
-	(void) __cond_lock(*ptlp,
-			   !(res = __follow_pte_pmd(mm, address, range,
-						    ptepp, pmdpp, ptlp)));
-	return res;
-}
-
 /**
  * follow_pfn - look up PFN at a user virtual address
  * @vma: memory mapping
@@ -4808,7 +4783,7 @@ int follow_pfn(struct vm_area_struct *vma, unsigned long address,
 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
 		return ret;
 
-	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
+	ret = follow_pte(vma->vm_mm, address, NULL, &ptep, NULL, &ptl);
 	if (ret)
 		return ret;
 	*pfn = pte_pfn(*ptep);
@@ -4829,7 +4804,7 @@ int follow_phys(struct vm_area_struct *vma,
 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
 		goto out;
 
-	if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
+	if (follow_pte(vma->vm_mm, address, NULL, &ptep, NULL, &ptl))
 		goto out;
 	pte = *ptep;
 
-- 
2.28.0

Re: simplify follow_pte a bit

[Christoph Hellwig]

On Thu, Oct 29, 2020 at 11:14:30AM +0100, Christoph Hellwig wrote:
> Hi Andrew,
> 
> this small series drops the not needed follow_pte_pmd exports, and
> simplifies the follow_pte family of functions a bit.

any comments?

Re: [PATCH 1/2] mm: unexport follow_pte_pmd

[Matthew Wilcox]

On Thu, Oct 29, 2020 at 11:14:31AM +0100, Christoph Hellwig wrote:
> follow_pte_pmd is only used by the DAX code, which can't be modular.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Re: [PATCH 2/2] mm: simplify follow_pte{,pmd}

[Matthew Wilcox]

On Thu, Oct 29, 2020 at 11:14:32AM +0100, Christoph Hellwig wrote:
> Merge __follow_pte_pmd, follow_pte_pmd and follow_pte into a single
> follow_pte function and just pass two additional NULL arguments for
> the two previous follow_pte callers.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

I'm not entirely convinced this is the right interface, but your patch
makes things better, so I approve.

Re: [PATCH 2/2] mm: simplify follow_pte{,pmd}

[Nick Desaulniers]

Sorry, I think this patch may be causing a regression for us for s390?
https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/432129279#L768

(via https://lore.kernel.org/linux-mm/20201029101432.47011-3-hch@lst.de)

Re: [PATCH 2/2] mm: simplify follow_pte{,pmd}

[Christoph Hellwig]

On Tue, Nov 10, 2020 at 06:21:22PM -0800, Nick Desaulniers wrote:
> Sorry, I think this patch may be causing a regression for us for s390?
> https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/432129279#L768
> 
> (via https://lore.kernel.org/linux-mm/20201029101432.47011-3-hch@lst.de)

Hmm, the call to follow_pte_pmd in the s390 code does not actually exist
in my tree.

Re: [PATCH 2/2] mm: simplify follow_pte{,pmd}

[Christian Borntraeger]

On 11.11.20 09:18, Christoph Hellwig wrote:
> On Tue, Nov 10, 2020 at 06:21:22PM -0800, Nick Desaulniers wrote:
>> Sorry, I think this patch may be causing a regression for us for s390?
>> https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/432129279#L768
>>
>> (via https://lore.kernel.org/linux-mm/20201029101432.47011-3-hch@lst.de)
> 
> Hmm, the call to follow_pte_pmd in the s390 code does not actually exist
> in my tree.

This is a mid-air collision in linux-next between

b2ff5796a934 ("mm: simplify follow_pte{,pmd}")
a67a88b0b8de ("s390/pci: remove races against pte updates")

Re: [PATCH 2/2] mm: simplify follow_pte{,pmd}

[Christoph Hellwig]

On Wed, Nov 11, 2020 at 09:26:20AM +0100, Christian Borntraeger wrote:
> 
> On 11.11.20 09:18, Christoph Hellwig wrote:
> > On Tue, Nov 10, 2020 at 06:21:22PM -0800, Nick Desaulniers wrote:
> >> Sorry, I think this patch may be causing a regression for us for s390?
> >> https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/432129279#L768
> >>
> >> (via https://lore.kernel.org/linux-mm/20201029101432.47011-3-hch@lst.de)
> > 
> > Hmm, the call to follow_pte_pmd in the s390 code does not actually exist
> > in my tree.
> 
> This is a mid-air collision in linux-next between
> 
> b2ff5796a934 ("mm: simplify follow_pte{,pmd}")
> a67a88b0b8de ("s390/pci: remove races against pte updates")

Ah.  The fixup is trivial: just s/follow_pte_pmd/follow_pte/.

Re: [PATCH 2/2] mm: simplify follow_pte{,pmd}

[Stephen Rothwell]

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Hi Christoph,

On Wed, 11 Nov 2020 09:28:42 +0100 Christoph Hellwig <hch@lst.de> wrote:
>
> On Wed, Nov 11, 2020 at 09:26:20AM +0100, Christian Borntraeger wrote:
> > 
> > On 11.11.20 09:18, Christoph Hellwig wrote:  
> > > On Tue, Nov 10, 2020 at 06:21:22PM -0800, Nick Desaulniers wrote:  
> > >> Sorry, I think this patch may be causing a regression for us for s390?
> > >> https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/432129279#L768
> > >>
> > >> (via https://lore.kernel.org/linux-mm/20201029101432.47011-3-hch@lst.de)  
> > > 
> > > Hmm, the call to follow_pte_pmd in the s390 code does not actually exist
> > > in my tree.  
> > 
> > This is a mid-air collision in linux-next between
> > 
> > b2ff5796a934 ("mm: simplify follow_pte{,pmd}")
> > a67a88b0b8de ("s390/pci: remove races against pte updates")  
> 
> Ah.  The fixup is trivial: just s/follow_pte_pmd/follow_pte/.

ok, so tomorrow I will add the following to the merge of the
akpm-current tree:

From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Wed, 11 Nov 2020 22:08:32 +1100
Subject: [PATCH] merge fix for "s390/pci: remove races against pte updates"

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
 arch/s390/pci/pci_mmio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c
index 1a6adbc68ee8..4a4993837413 100644
--- a/arch/s390/pci/pci_mmio.c
+++ b/arch/s390/pci/pci_mmio.c
@@ -173,7 +173,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmio_addr,
 	if (!(vma->vm_flags & VM_WRITE))
 		goto out_unlock_mmap;
 
-	ret = follow_pte_pmd(vma->vm_mm, mmio_addr, NULL, &ptep, NULL, &ptl);
+	ret = follow_pte(vma->vm_mm, mmio_addr, NULL, &ptep, NULL, &ptl);
 	if (ret)
 		goto out_unlock_mmap;
 
@@ -317,7 +317,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_read, unsigned long, mmio_addr,
 	if (!(vma->vm_flags & VM_WRITE))
 		goto out_unlock_mmap;
 
-	ret = follow_pte_pmd(vma->vm_mm, mmio_addr, NULL, &ptep, NULL, &ptl);
+	ret = follow_pte(vma->vm_mm, mmio_addr, NULL, &ptep, NULL, &ptl);
 	if (ret)
 		goto out_unlock_mmap;
 
-- 
2.29.2

-- 
Cheers,
Stephen Rothwell

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