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 83cd904d271b: "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 <mpatocka@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index f581a18c0d4d7d07aac5cdfa8fb443106e3d5e92..83e7141c3982fe2b9b940e4f13cf89f3c6c26d2f 100644 (file)
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -333,13 +333,15 @@ try_again:
                 * 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
index 06b145fb64ab59a399344bc73ca277be0e39ed7b..47296fee23dbaa67c3408227d7653037a371bcdf 100644 (file)
--- 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
index 4f4f53bdc65de30d11c637b2bc745aa1333a16bd..ef726e8aa8e9ca56c0713abfa4b621f44a210d4c 100644 (file)
--- 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
index 5a688a2756bec54435adbd5f3c13a33fbdd2c11e..f437d054c3bf6884fd5ba6f18338fbf7272c43a4 100644 (file)
--- 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;