mm: make the vma list be doubly linked

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>

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index b8bb9a6a1f37b71cae90c33ff84e75d2d780226a..ee7e258627f9f5b9999e4c3033f7fa78c5927b48 100644 (file)
--- 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 856eac3ec52eb1a11fa6405d3e870da796c778ee..b7e9d60a675d3a08a1096ce725380229217d9fa3 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -300,7 +300,7 @@ 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;
@@ -328,6 +328,7 @@ 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;
 
@@ -359,7 +360,7 @@ 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;
@@ -392,6 +393,8 @@ 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 31003338b978b78ef66d4579033cdd1d3ebd1a16..331e51af38c9c950c8295fa125c67d00ba540025 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -388,17 +388,23 @@ 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 (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,
@@ -483,7 +489,11 @@ 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;
@@ -1915,6 +1925,7 @@ 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--;
@@ -1922,6 +1933,8 @@ 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 efa9a380335eed137c30d5c762c5a5cdae469b9c..88ff091eb07a23dcaee1e8e6d0cc70927183b89b 100644 (file)
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -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)
 {
-       struct vm_area_struct *pvma, **pp;
+       struct vm_area_struct *pvma, **pp, *next;
        struct address_space *mapping;
        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;
        }
 
-       vma->vm_next = *pp;
+       next = *pp;
        *pp = vma;
+       vma->vm_next = next;
+       if (next)
+               next->vm_prev = vma;
 }
 
 /*