mm: make the vma list be doubly linked

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>

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 4c14942a0ee36fa994abdf91fa218d68b9e4052d..32fdbd46b8e5ee126687650e4a1c0548530ce64f 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -287,7 +287,7 @@ 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;
@@ -315,6 +315,7 @@ 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;
 
@@ -346,7 +347,7 @@ 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;
@@ -379,6 +380,8 @@ 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 456ec6f278897a560bd915e6d84297ac3de7ddef..3867cfc21cc796b6e885b3b9531c64f1033f7f3d 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,
@@ -485,7 +491,11 @@ 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;
@@ -1900,6 +1910,7 @@ 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--;
@@ -1907,6 +1918,8 @@ 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 63fa17d121f027ca5c75f09eab994db346316d2b..28994ee251c35a9d706919012888aec57a2eeac4 100644 (file)
--- 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;
 }
 
 /*