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mm/mmap.c: find_vma(): remove unnecessary if(mm) check 

The "if (mm)" check is not required in find_vma, as the kernel code
calls find_vma only when it is absolutely sure that the mm_struct arg to
it is non-NULL.

Remove the if(mm) check and adding the a WARN_ONCE(!mm) for now.  This
will serve the purpose of mandating that the execution
context(user-mode/kernel-mode) be known before find_vma is called.  Also
fixed 2 checkpatch.pl errors in the declaration of the rb_node and
vma_tmp local variables.

I was browsing through the internet and read a discussion at
https://lkml.org/lkml/2012/3/27/342 which discusses removal of the
validation check within find_vma.  Since no-one responded, I decided to
send this patch with Andrew's suggestions.

[akpm@linux-foundation.org: add remove-me comment]
Signed-off-by: Rajman Mekaco <rajman.mekaco@gmail.com>
Cc: Kautuk Consul <consul.kautuk@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
5bit-waveforms
Rajman Mekaco 2012-05-29 15:06:21 -07:00 committed by Linus Torvalds
parent 4d67d86053
commit 841e31e5cc
1 changed files with 23 additions and 22 deletions
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45
mm/mmap.c
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@ -1639,33 +1639,34 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
{
struct vm_area_struct *vma = NULL;
if (mm) {
/* Check the cache first. */
/* (Cache hit rate is typically around 35%.) */
vma = mm->mmap_cache;
if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
struct rb_node * rb_node;
if (WARN_ON_ONCE(!mm)) /* Remove this in linux-3.6 */
return NULL;
rb_node = mm->mm_rb.rb_node;
vma = NULL;
/* Check the cache first. */
/* (Cache hit rate is typically around 35%.) */
vma = mm->mmap_cache;
if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
struct rb_node *rb_node;
while (rb_node) {
struct vm_area_struct * vma_tmp;
rb_node = mm->mm_rb.rb_node;
vma = NULL;
vma_tmp = rb_entry(rb_node,
struct vm_area_struct, vm_rb);
while (rb_node) {
struct vm_area_struct *vma_tmp;
if (vma_tmp->vm_end > addr) {
vma = vma_tmp;
if (vma_tmp->vm_start <= addr)
break;
rb_node = rb_node->rb_left;
} else
rb_node = rb_node->rb_right;
}
if (vma)
mm->mmap_cache = vma;
vma_tmp = rb_entry(rb_node,
struct vm_area_struct, vm_rb);
if (vma_tmp->vm_end > addr) {
vma = vma_tmp;
if (vma_tmp->vm_start <= addr)
break;
rb_node = rb_node->rb_left;
} else
rb_node = rb_node->rb_right;
}
if (vma)
mm->mmap_cache = vma;
}
return vma;
}