path: root/mm/util.c
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authorNamhyung Kim <namhyung@gmail.com>2011-05-24 17:11:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-25 08:39:05 -0700
commit6038def0d11b322019d0dbb43f2a611247dfbdb6 (patch)
tree3b7bd8a20af5749566bfba9ca39a3d0c2cc25e0a /mm/util.c
parentac3bbec5ec69b973317677e038de2d1a0c90c18c (diff)
mm: nommu: sort mm->mmap list properly
When I was reading nommu code, I found that it handles the vma list/tree in an unusual way. IIUC, because there can be more than one identical/overrapped vmas in the list/tree, it sorts the tree more strictly and does a linear search on the tree. But it doesn't applied to the list (i.e. the list could be constructed in a different order than the tree so that we can't use the list when finding the first vma in that order). Since inserting/sorting a vma in the tree and link is done at the same time, we can easily construct both of them in the same order. And linear searching on the tree could be more costly than doing it on the list, it can be converted to use the list. Also, after the commit 297c5eee3724 ("mm: make the vma list be doubly linked") made the list be doubly linked, there were a couple of code need to be fixed to construct the list properly. Patch 1/6 is a preparation. It maintains the list sorted same as the tree and construct doubly-linked list properly. Patch 2/6 is a simple optimization for the vma deletion. Patch 3/6 and 4/6 convert tree traversal to list traversal and the rest are simple fixes and cleanups. This patch: @vma added into @mm should be sorted by start addr, end addr and VMA struct addr in that order because we may get identical VMAs in the @mm. However this was true only for the rbtree, not for the list. This patch fixes this by remembering 'rb_prev' during the tree traversal like find_vma_prepare() does and linking the @vma via __vma_link_list(). After this patch, we can iterate the whole VMAs in correct order simply by using @mm->mmap list. [akpm@linux-foundation.org: avoid duplicating __vma_link_list()] Signed-off-by: Namhyung Kim <namhyung@gmail.com> Acked-by: Greg Ungerer <gerg@uclinux.org> Cc: David Howells <dhowells@redhat.com> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/util.c')
1 files changed, 24 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c
index e7b103a6fd2..88ea1bd661c 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -6,6 +6,8 @@
#include <linux/sched.h>
#include <asm/uaccess.h>
+#include "internal.h"
#include <trace/events/kmem.h>
@@ -215,6 +217,28 @@ char *strndup_user(const char __user *s, long n)
+void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
+ struct vm_area_struct *prev, struct rb_node *rb_parent)
+ struct vm_area_struct *next;
+ vma->vm_prev = prev;
+ if (prev) {
+ next = prev->vm_next;
+ prev->vm_next = vma;
+ } else {
+ mm->mmap = vma;
+ if (rb_parent)
+ next = rb_entry(rb_parent,
+ struct vm_area_struct, vm_rb);
+ else
+ next = NULL;
+ }
+ vma->vm_next = next;
+ if (next)
+ next->vm_prev = vma;
#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
void arch_pick_mmap_layout(struct mm_struct *mm)