vm: avoid using find_vma_prev() unnecessarily

Several users of "find_vma_prev()" were not in fact interested in the previous vma if there was no primary vma to be found either. And in those cases, we're much better off just using the regular "find_vma()", and then "prev" can be looked up by just checking vma->vm_prev. The find_vma_prev() semantics are fairly subtle (see Mikulas' recent commit 83cd904: "mm: fix find_vma_prev"), and the whole "return prev by reference" means that it generates worse code too. Thus this "let's avoid using this inconvenient and clearly too subtle interface when we don't really have to" patch. Cc: Mikulas Patocka <[email protected]> Cc: KOSAKI Motohiro <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
mrcsosa · Mar 7, 2012 · 097d591 · 097d591
1 parent 71fece9
commit 097d591
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Showing 4 changed files with 9 additions and 4 deletions.
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
@@ -333,13 +333,15 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 		 * Lookup failure means no vma is above this address,
 		 * i.e. return with success:
 		 */
-		if (!(vma = find_vma_prev(mm, addr, &prev_vma)))
+		vma = find_vma(mm, add);
+		if (!vma)
 			return addr;
 
 		/*
 		 * new region fits between prev_vma->vm_end and
 		 * vma->vm_start, use it:
 		 */
+		prev_vma = vma->vm_prev;
 		if (addr + len <= vma->vm_start &&
 		            (!prev_vma || (addr >= prev_vma->vm_end))) {
 			/* remember the address as a hint for next time */

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
@@ -640,10 +640,11 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
 	unsigned long vmstart;
 	unsigned long vmend;
 
-	vma = find_vma_prev(mm, start, &prev);
+	vma = find_vma(mm, start);
 	if (!vma || vma->vm_start > start)
 		return -EFAULT;
 
+	prev = vma->vm_prev;
 	if (start > vma->vm_start)
 		prev = vma;
 

diff --git a/mm/mlock.c b/mm/mlock.c
@@ -385,10 +385,11 @@ static int do_mlock(unsigned long start, size_t len, int on)
 		return -EINVAL;
 	if (end == start)
 		return 0;
-	vma = find_vma_prev(current->mm, start, &prev);
+	vma = find_vma(current->mm, start);
 	if (!vma || vma->vm_start > start)
 		return -ENOMEM;
 
+	prev = vma->vm_prev;
 	if (start > vma->vm_start)
 		prev = vma;
 

diff --git a/mm/mprotect.c b/mm/mprotect.c
@@ -262,10 +262,11 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 
 	down_write(&current->mm->mmap_sem);
 
-	vma = find_vma_prev(current->mm, start, &prev);
+	vma = find_vma(current->mm, start);
 	error = -ENOMEM;
 	if (!vma)
 		goto out;
+	prev = vma->vm_prev;
 	if (unlikely(grows & PROT_GROWSDOWN)) {
 		if (vma->vm_start >= end)
 			goto out;