untangling do_mremap(), part 1

Take locating vma and checks on it to a separate helper (it will be
shared between MREMAP_FIXED/non-MREMAP_FIXED cases when we split
them in the next patch)

Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 55 insertions, 33 deletions

diff --git a/mm/mremap.c b/mm/mremap.c
index 97bff2547719..67761361c469 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -261,6 +261,58 @@ static unsigned long move_vma(struct vm_area_struct *vma,
         return new_addr;
 }
 
+static struct vm_area_struct *vma_to_resize(unsigned long addr,
+        unsigned long old_len, unsigned long new_len, unsigned long *p)
+{
+        struct mm_struct *mm = current->mm;
+        struct vm_area_struct *vma = find_vma(mm, addr);
+
+        if (!vma || vma->vm_start > addr)
+                goto Efault;
+
+        if (is_vm_hugetlb_page(vma))
+                goto Einval;
+
+        /* We can't remap across vm area boundaries */
+        if (old_len > vma->vm_end - addr)
+                goto Efault;
+
+        if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
+                if (new_len > old_len)
+                        goto Efault;
+        }
+
+        if (vma->vm_flags & VM_LOCKED) {
+                unsigned long locked, lock_limit;
+                locked = mm->locked_vm << PAGE_SHIFT;
+                lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
+                locked += new_len - old_len;
+                if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+                        goto Eagain;
+        }
+
+        if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
+                goto Enomem;
+
+        if (vma->vm_flags & VM_ACCOUNT) {
+                unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
+                if (security_vm_enough_memory(charged))
+                        goto Efault;
+                *p = charged;
+        }
+
+        return vma;
+
+Efault: /* very odd choice for most of the cases, but... */
+        return ERR_PTR(-EFAULT);
+Einval:
+        return ERR_PTR(-EINVAL);
+Enomem:
+        return ERR_PTR(-ENOMEM);
+Eagain:
+        return ERR_PTR(-EAGAIN);
+}
+
 /*
  * Expand (or shrink) an existing mapping, potentially moving it at the
  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
@@ -340,41 +392,12 @@ unsigned long do_mremap(unsigned long addr,
         /*
          * Ok, we need to grow..  or relocate.
          */
-        ret = -EFAULT;
-        vma = find_vma(mm, addr);
-        if (!vma || vma->vm_start > addr)
-                goto out;
-        if (is_vm_hugetlb_page(vma)) {
-                ret = -EINVAL;
-                goto out;
-        }
-        /* We can't remap across vm area boundaries */
-        if (old_len > vma->vm_end - addr)
-                goto out;
-        if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
-                if (new_len > old_len)
-                        goto out;
-        }
-        if (vma->vm_flags & VM_LOCKED) {
-                unsigned long locked, lock_limit;
-                locked = mm->locked_vm << PAGE_SHIFT;
-                lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
-                locked += new_len - old_len;
-                ret = -EAGAIN;
-                if (locked > lock_limit && !capable(CAP_IPC_LOCK))
-                        goto out;
-        }
-        if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
-                ret = -ENOMEM;
+        vma = vma_to_resize(addr, old_len, new_len, &charged);
+        if (IS_ERR(vma)) {
+                ret = PTR_ERR(vma);
                 goto out;
         }
 
-        if (vma->vm_flags & VM_ACCOUNT) {
-                charged = (new_len - old_len) >> PAGE_SHIFT;
-                if (security_vm_enough_memory(charged))
-                        goto out_nc;
-        }
-
         /* old_len exactly to the end of the area..
          * And we're not relocating the area.
          */
@@ -430,7 +453,6 @@ unsigned long do_mremap(unsigned long addr,
 out:
         if (ret & ~PAGE_MASK)
                 vm_unacct_memory(charged);
-out_nc:
         return ret;
 }