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-   -   mm: make the vma list be doubly linked (http://www.linux-archive.org/ubuntu-kernel-team/602163-mm-make-vma-list-doubly-linked.html)

Paolo Pisati 11-24-2011 09:07 AM

mm: make the vma list be doubly linked
 
From: Linus Torvalds <torvalds@linux-foundation.org>

commit 297c5eee372478fc32fec5fe8eed711eedb13f3d upstream.

It's a really simple list, and several of the users want to go backwards
in it to find the previous vma. So rather than have to look up the
previous entry with 'find_vma_prev()' or something similar, just make it
doubly linked instead.

Tested-by: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

commit f5981434834ad0373b8fc58deabf6493564ae42a master

BugLink: http://launchpad.net/bugs/893190

Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
---
include/linux/mm_types.h | 2 +-
kernel/fork.c | 7 +++++--
mm/mmap.c | 22 ++++++++++++++++++----
mm/nommu.c | 7 +++++--
4 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index f478e39..8a8a765 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -134,7 +134,7 @@ struct vm_area_struct {
within vm_mm. */

/* linked list of VM areas per task, sorted by address */
- struct vm_area_struct *vm_next;
+ struct vm_area_struct *vm_next, *vm_prev;

pgprot_t vm_page_prot; /* Access permissions of this VMA. */
unsigned long vm_flags; /* Flags, see mm.h. */
diff --git a/kernel/fork.c b/kernel/fork.c
index 7fbc5e3..49ffdad 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -301,7 +301,7 @@ out:
#ifdef CONFIG_MMU
static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
{
- struct vm_area_struct *mpnt, *tmp, **pprev;
+ struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
struct rb_node **rb_link, *rb_parent;
int retval;
unsigned long charge;
@@ -329,6 +329,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
if (retval)
goto out;

+ prev = NULL;
for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
struct file *file;

@@ -360,7 +361,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
goto fail_nomem_anon_vma_fork;
tmp->vm_flags &= ~VM_LOCKED;
tmp->vm_mm = mm;
- tmp->vm_next = NULL;
+ tmp->vm_next = tmp->vm_prev = NULL;
file = tmp->vm_file;
if (file) {
struct inode *inode = file->f_path.dentry->d_inode;
@@ -393,6 +394,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
*/
*pprev = tmp;
pprev = &tmp->vm_next;
+ tmp->vm_prev = prev;
+ prev = tmp;

__vma_link_rb(mm, tmp, rb_link, rb_parent);
rb_link = &tmp->vm_rb.rb_right;
diff --git a/mm/mmap.c b/mm/mmap.c
index f487849..a8d1651 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -401,19 +401,26 @@ static inline 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 (vma->vm_flags & VM_EXEC)
arch_add_exec_range(mm, vma->vm_end);
if (prev) {
- vma->vm_next = prev->vm_next;
+ next = prev->vm_next;
prev->vm_next = vma;
} else {
mm->mmap = vma;
if (rb_parent)
- vma->vm_next = rb_entry(rb_parent,
+ next = rb_entry(rb_parent,
struct vm_area_struct, vm_rb);
else
- vma->vm_next = NULL;
+ next = NULL;
}
+ vma->vm_next = next;
+ if (next)
+ next->vm_prev = vma;
}

void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
@@ -500,7 +507,11 @@ static inline void
__vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev)
{
- prev->vm_next = vma->vm_next;
+ struct vm_area_struct *next = vma->vm_next;
+
+ prev->vm_next = next;
+ if (next)
+ next->vm_prev = prev;
rb_erase(&vma->vm_rb, &mm->mm_rb);
if (mm->mmap_cache == vma)
mm->mmap_cache = prev;
@@ -2013,6 +2024,7 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr;

insertion_point = (prev ? &prev->vm_next : &mm->mmap);
+ vma->vm_prev = NULL;
do {
rb_erase(&vma->vm_rb, &mm->mm_rb);
mm->map_count--;
@@ -2020,6 +2032,8 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
vma = vma->vm_next;
} while (vma && vma->vm_start < end);
*insertion_point = vma;
+ if (vma)
+ vma->vm_prev = prev;
tail_vma->vm_next = NULL;
if (mm->unmap_area == arch_unmap_area)
addr = prev ? prev->vm_end : mm->mmap_base;
diff --git a/mm/nommu.c b/mm/nommu.c
index b76f3ee..e48b38c 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -609,7 +609,7 @@ static void protect_vma(struct vm_area_struct *vma, unsigned long flags)
*/
static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
{
- struct vm_area_struct *pvma, **pp;
+ struct vm_area_struct *pvma, **pp, *next;
struct address_space *mapping;
struct rb_node **p, *parent;

@@ -669,8 +669,11 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
break;
}

- vma->vm_next = *pp;
+ next = *pp;
*pp = vma;
+ vma->vm_next = next;
+ if (next)
+ next->vm_prev = vma;
}

/*
--
1.7.5.4


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