The patch titled
Subject: mremap: don't do uneccesary checks if new_len == old_len
has been added to the -mm tree. Its filename is
mremap-dont-do-uneccesary-checks-if-new_len-==-old_len.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mremap-dont-do-uneccesary-checks-if-new_len-%3D%3D-old_len.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mremap-dont-do-uneccesary-checks-if-new_len-%3D%3D-old_len.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: mremap: don't do uneccesary checks if new_len == old_len
The "new_len > old_len" branch in vma_to_resize() looks very confusing.
It only covers the VM_DONTEXPAND/pgoff checks but everything below is
equally unneeded if new_len == old_len.
Change this code to return if "new_len == old_len", new_len < old_len is
not possible, otherwise the code below is wrong anyway.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Benjamin LaHaise <bcrl@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mremap.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff -puN mm/mremap.c~mremap-dont-do-uneccesary-checks-if-new_len-==-old_len mm/mremap.c
--- a/mm/mremap.c~mremap-dont-do-uneccesary-checks-if-new_len-==-old_len
+++ a/mm/mremap.c
@@ -346,6 +346,7 @@ static struct vm_area_struct *vma_to_res
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = find_vma(mm, addr);
+ unsigned long pgoff;
if (!vma || vma->vm_start > addr)
return ERR_PTR(-EFAULT);
@@ -357,17 +358,17 @@ static struct vm_area_struct *vma_to_res
if (old_len > vma->vm_end - addr)
return ERR_PTR(-EFAULT);
+ if (new_len == old_len)
+ return vma;
+
/* Need to be careful about a growing mapping */
- if (new_len > old_len) {
- unsigned long pgoff;
+ pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
+ pgoff += vma->vm_pgoff;
+ if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
+ return ERR_PTR(-EINVAL);
- if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
- return ERR_PTR(-EFAULT);
- pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
- pgoff += vma->vm_pgoff;
- if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
- return ERR_PTR(-EINVAL);
- }
+ if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
+ return ERR_PTR(-EFAULT);
if (vma->vm_flags & VM_LOCKED) {
unsigned long locked, lock_limit;
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
mremap-dont-leak-new_vma-if-f_op-mremap-fails.patch
mm-move-mremap-from-file_operations-to-vm_operations_struct.patch
mremap-dont-do-mm_populatenew_addr-on-failure.patch
mremap-dont-do-uneccesary-checks-if-new_len-==-old_len.patch
mremap-simplify-the-overlap-check-in-mremap_to.patch
kmod-bunch-of-internal-functions-renames.patch
kmod-add-up-to-date-explanations-on-the-purpose-of-each-asynchronous-levels.patch
kmod-remove-unecessary-explicit-wide-cpu-affinity-setting.patch
linux-next.patch
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