The patch titled
Subject: mm/mmap.c: find_vma(): remove unnecessary if(mm) check
has been added to the -mm tree. Its filename is
mm-mmapc-find_vma-remove-unnecessary-ifmm-check.patch
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From: Rajman Mekaco <rajman.mekaco@xxxxxxxxx>
Subject: 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.
Signed-off-by: Rajman Mekaco <rajman.mekaco@xxxxxxxxx>
Cc: Kautuk Consul <consul.kautuk@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 53 ++++++++++++++++++++++++++--------------------------
1 file changed, 27 insertions(+), 26 deletions(-)
diff -puN mm/mmap.c~mm-mmapc-find_vma-remove-unnecessary-ifmm-check mm/mmap.c
--- a/mm/mmap.c~mm-mmapc-find_vma-remove-unnecessary-ifmm-check
+++ a/mm/mmap.c
@@ -1639,33 +1639,34 @@ struct vm_area_struct *find_vma(struct m
{
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;
-
- rb_node = mm->mm_rb.rb_node;
- vma = NULL;
-
- while (rb_node) {
- struct vm_area_struct * vma_tmp;
-
- 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;
+ if (WARN_ON_ONCE(!mm))
+ return 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;
+
+ rb_node = mm->mm_rb.rb_node;
+ vma = NULL;
+
+ while (rb_node) {
+ struct vm_area_struct *vma_tmp;
+
+ 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;
}
_
Subject: Subject: mm/mmap.c: find_vma(): remove unnecessary if(mm) check
Patches currently in -mm which might be from rajman.mekaco@xxxxxxxxx are
mm-mmapc-find_vma-remove-unnecessary-ifmm-check.patch
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