Commit 841e31e5 authored by Rajman Mekaco's avatar Rajman Mekaco Committed by Linus Torvalds

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: default avatarRajman 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: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4d67d860
...@@ -1639,18 +1639,20 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) ...@@ -1639,18 +1639,20 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
{ {
struct vm_area_struct *vma = NULL; struct vm_area_struct *vma = NULL;
if (mm) { if (WARN_ON_ONCE(!mm)) /* Remove this in linux-3.6 */
return NULL;
/* Check the cache first. */ /* Check the cache first. */
/* (Cache hit rate is typically around 35%.) */ /* (Cache hit rate is typically around 35%.) */
vma = mm->mmap_cache; vma = mm->mmap_cache;
if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) { if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
struct rb_node * rb_node; struct rb_node *rb_node;
rb_node = mm->mm_rb.rb_node; rb_node = mm->mm_rb.rb_node;
vma = NULL; vma = NULL;
while (rb_node) { while (rb_node) {
struct vm_area_struct * vma_tmp; struct vm_area_struct *vma_tmp;
vma_tmp = rb_entry(rb_node, vma_tmp = rb_entry(rb_node,
struct vm_area_struct, vm_rb); struct vm_area_struct, vm_rb);
...@@ -1666,7 +1668,6 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) ...@@ -1666,7 +1668,6 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
if (vma) if (vma)
mm->mmap_cache = vma; mm->mmap_cache = vma;
} }
}
return vma; return vma;
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment