[PATCH] mm/hmm: Simplify hmm_vma_walk_pud slightly

[Steven Price]

By refactoring to deal with the !pud_huge(pud) || !pud_devmap(pud)
condition early it's possible to remove the 'ret' variable and remove a
level of indentation from half the function making the code easier to
read.

No functional change.

Signed-off-by: Steven Price <steven.price at arm.com>
---
Thanks to Jason's changes there were only two code paths left using
the out_unlock label so it seemed like a good opportunity to refactor.
---
 mm/hmm.c | 69 ++++++++++++++++++++++++++------------------------------
 1 file changed, 32 insertions(+), 37 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index ca33d086bdc1..0117c86426d1 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -466,8 +466,10 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 	struct hmm_range *range = hmm_vma_walk->range;
 	unsigned long addr = start;
 	pud_t pud;
-	int ret = 0;
 	spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
+	unsigned long i, npages, pfn;
+	uint64_t *pfns, cpu_flags;
+	bool fault, write_fault;
 
 	if (!ptl)
 		return 0;
@@ -481,50 +483,43 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
 		return hmm_vma_walk_hole(start, end, -1, walk);
 	}
 
-	if (pud_huge(pud) && pud_devmap(pud)) {
-		unsigned long i, npages, pfn;
-		uint64_t *pfns, cpu_flags;
-		bool fault, write_fault;
+	if (!pud_huge(pud) || !pud_devmap(pud)) {
+		/* Ask for the PUD to be split */
+		walk->action = ACTION_SUBTREE;
+		spin_unlock(ptl);
+		return 0;
+	}
 
-		if (!pud_present(pud)) {
-			spin_unlock(ptl);
-			return hmm_vma_walk_hole(start, end, -1, walk);
-		}
+	if (!pud_present(pud)) {
+		spin_unlock(ptl);
+		return hmm_vma_walk_hole(start, end, -1, walk);
+	}
 
-		i = (addr - range->start) >> PAGE_SHIFT;
-		npages = (end - addr) >> PAGE_SHIFT;
-		pfns = &range->pfns[i];
+	i = (addr - range->start) >> PAGE_SHIFT;
+	npages = (end - addr) >> PAGE_SHIFT;
+	pfns = &range->pfns[i];
 
-		cpu_flags = pud_to_hmm_pfn_flags(range, pud);
-		hmm_range_need_fault(hmm_vma_walk, pfns, npages,
-				     cpu_flags, &fault, &write_fault);
-		if (fault || write_fault) {
-			spin_unlock(ptl);
-			return hmm_vma_walk_hole_(addr, end, fault, write_fault,
-						  walk);
-		}
+	cpu_flags = pud_to_hmm_pfn_flags(range, pud);
+	hmm_range_need_fault(hmm_vma_walk, pfns, npages,
+			     cpu_flags, &fault, &write_fault);
+	if (fault || write_fault) {
+		spin_unlock(ptl);
+		return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
+	}
 
-		pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
-		for (i = 0; i < npages; ++i, ++pfn) {
-			hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
-					      hmm_vma_walk->pgmap);
-			if (unlikely(!hmm_vma_walk->pgmap)) {
-				ret = -EBUSY;
-				goto out_unlock;
-			}
-			pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
-				  cpu_flags;
+	pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
+	for (i = 0; i < npages; ++i, ++pfn) {
+		hmm_vma_walk->pgmap = get_dev_pagemap(pfn, hmm_vma_walk->pgmap);
+		if (unlikely(!hmm_vma_walk->pgmap)) {
+			spin_unlock(ptl);
+			return -EBUSY;
 		}
-		hmm_vma_walk->last = end;
-		goto out_unlock;
+		pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags;
 	}
+	hmm_vma_walk->last = end;
 
-	/* Ask for the PUD to be split */
-	walk->action = ACTION_SUBTREE;
-
-out_unlock:
 	spin_unlock(ptl);
-	return ret;
+	return 0;
 }
 #else
 #define hmm_vma_walk_pud	NULL
-- 
2.20.1