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mm: make the vma list be doubly linked

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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>
This commit is contained in:
Linus Torvalds 2010-08-20 16:24:55 -07:00
parent 36423a5ed5
commit 297c5eee37
4 changed files with 28 additions and 9 deletions
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2
include/linux/mm_types.h
View File

@ -134,7 +134,7 @@ struct vm_area_struct {
within vm_mm. */ within vm_mm. */
/* linked list of VM areas per task, sorted by address */ /* 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. */ pgprot_t vm_page_prot; /* Access permissions of this VMA. */
unsigned long vm_flags; /* Flags, see mm.h. */ unsigned long vm_flags; /* Flags, see mm.h. */

7
kernel/fork.c
View File

@ -300,7 +300,7 @@ out:
#ifdef CONFIG_MMU #ifdef CONFIG_MMU
static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 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; struct rb_node **rb_link, *rb_parent;
int retval; int retval;
unsigned long charge; unsigned long charge;
@ -328,6 +328,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
if (retval) if (retval)
goto out; goto out;
prev = NULL;
for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
struct file *file; struct file *file;
@ -359,7 +360,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
goto fail_nomem_anon_vma_fork; goto fail_nomem_anon_vma_fork;
tmp->vm_flags &= ~VM_LOCKED; tmp->vm_flags &= ~VM_LOCKED;
tmp->vm_mm = mm; tmp->vm_mm = mm;
tmp->vm_next = NULL; tmp->vm_next = tmp->vm_prev = NULL;
file = tmp->vm_file; file = tmp->vm_file;
if (file) { if (file) {
struct inode *inode = file->f_path.dentry->d_inode; struct inode *inode = file->f_path.dentry->d_inode;
@ -392,6 +393,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
*/ */
*pprev = tmp; *pprev = tmp;
pprev = &tmp->vm_next; pprev = &tmp->vm_next;
tmp->vm_prev = prev;
prev = tmp;
__vma_link_rb(mm, tmp, rb_link, rb_parent); __vma_link_rb(mm, tmp, rb_link, rb_parent);
rb_link = &tmp->vm_rb.rb_right; rb_link = &tmp->vm_rb.rb_right;

21
mm/mmap.c
View File

@ -388,17 +388,23 @@ static inline void
__vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma, __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 *prev, struct rb_node *rb_parent)
{ {
struct vm_area_struct *next;
vma->vm_prev = prev;
if (prev) { if (prev) {
vma->vm_next = prev->vm_next; next = prev->vm_next;
prev->vm_next = vma; prev->vm_next = vma;
} else { } else {
mm->mmap = vma; mm->mmap = vma;
if (rb_parent) if (rb_parent)
vma->vm_next = rb_entry(rb_parent, next = rb_entry(rb_parent,
struct vm_area_struct, vm_rb); struct vm_area_struct, vm_rb);
else 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, void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
@ -483,7 +489,11 @@ static inline void
__vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma, __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev) 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); rb_erase(&vma->vm_rb, &mm->mm_rb);
if (mm->mmap_cache == vma) if (mm->mmap_cache == vma)
mm->mmap_cache = prev; mm->mmap_cache = prev;
@ -1915,6 +1925,7 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr; unsigned long addr;
insertion_point = (prev ? &prev->vm_next : &mm->mmap); insertion_point = (prev ? &prev->vm_next : &mm->mmap);
vma->vm_prev = NULL;
do { do {
rb_erase(&vma->vm_rb, &mm->mm_rb); rb_erase(&vma->vm_rb, &mm->mm_rb);
mm->map_count--; mm->map_count--;
@ -1922,6 +1933,8 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
vma = vma->vm_next; vma = vma->vm_next;
} while (vma && vma->vm_start < end); } while (vma && vma->vm_start < end);
*insertion_point = vma; *insertion_point = vma;
if (vma)
vma->vm_prev = prev;
tail_vma->vm_next = NULL; tail_vma->vm_next = NULL;
if (mm->unmap_area == arch_unmap_area) if (mm->unmap_area == arch_unmap_area)
addr = prev ? prev->vm_end : mm->mmap_base; addr = prev ? prev->vm_end : mm->mmap_base;

7
mm/nommu.c
View File

@ -604,7 +604,7 @@ 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) 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 address_space *mapping;
struct rb_node **p, *parent; struct rb_node **p, *parent;
@ -664,8 +664,11 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
break; break;
} }
vma->vm_next = *pp; next = *pp;
*pp = vma; *pp = vma;
vma->vm_next = next;
if (next)
next->vm_prev = vma;
} }
/* /*