do_mremap() untangling, part 2
Al Viro [Tue, 24 Nov 2009 12:28:07 +0000 (07:28 -0500)]
Take the MREMAP_FIXED into a separate helper, simplify the living
hell out of conditions in both cases.

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>

mm/mremap.c

index 6776136..5f34617 100644 (file)
@@ -313,6 +313,59 @@ Eagain:
        return ERR_PTR(-EAGAIN);
 }
 
+static unsigned long mremap_to(unsigned long addr,
+       unsigned long old_len, unsigned long new_addr,
+       unsigned long new_len)
+{
+       struct mm_struct *mm = current->mm;
+       struct vm_area_struct *vma;
+       unsigned long ret = -EINVAL;
+       unsigned long charged = 0;
+
+       if (new_addr & ~PAGE_MASK)
+               goto out;
+
+       if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
+               goto out;
+
+       /* Check if the location we're moving into overlaps the
+        * old location at all, and fail if it does.
+        */
+       if ((new_addr <= addr) && (new_addr+new_len) > addr)
+               goto out;
+
+       if ((addr <= new_addr) && (addr+old_len) > new_addr)
+               goto out;
+
+       ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
+       if (ret)
+               goto out;
+
+       ret = do_munmap(mm, new_addr, new_len);
+       if (ret)
+               goto out;
+
+       if (old_len >= new_len) {
+               ret = do_munmap(mm, addr+new_len, old_len - new_len);
+               if (ret && old_len != new_len)
+                       goto out;
+               old_len = new_len;
+       }
+
+       vma = vma_to_resize(addr, old_len, new_len, &charged);
+       if (IS_ERR(vma)) {
+               ret = PTR_ERR(vma);
+               goto out;
+       }
+
+       ret = move_vma(vma, addr, old_len, new_len, new_addr);
+       if (ret & ~PAGE_MASK)
+               vm_unacct_memory(charged);
+
+out:
+       return ret;
+}
+
 /*
  * Expand (or shrink) an existing mapping, potentially moving it at the
  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
@@ -346,32 +399,10 @@ unsigned long do_mremap(unsigned long addr,
        if (!new_len)
                goto out;
 
-       /* new_addr is only valid if MREMAP_FIXED is specified */
        if (flags & MREMAP_FIXED) {
-               if (new_addr & ~PAGE_MASK)
-                       goto out;
-               if (!(flags & MREMAP_MAYMOVE))
-                       goto out;
-
-               if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
-                       goto out;
-
-               /* Check if the location we're moving into overlaps the
-                * old location at all, and fail if it does.
-                */
-               if ((new_addr <= addr) && (new_addr+new_len) > addr)
-                       goto out;
-
-               if ((addr <= new_addr) && (addr+old_len) > new_addr)
-                       goto out;
-
-               ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
-               if (ret)
-                       goto out;
-
-               ret = do_munmap(mm, new_addr, new_len);
-               if (ret)
-                       goto out;
+               if (flags & MREMAP_MAYMOVE)
+                       ret = mremap_to(addr, old_len, new_addr, new_len);
+               goto out;
        }
 
        /*
@@ -384,13 +415,11 @@ unsigned long do_mremap(unsigned long addr,
                if (ret && old_len != new_len)
                        goto out;
                ret = addr;
-               if (!(flags & MREMAP_FIXED) || (new_addr == addr))
-                       goto out;
-               old_len = new_len;
+               goto out;
        }
 
        /*
-        * Ok, we need to grow..  or relocate.
+        * Ok, we need to grow..
         */
        vma = vma_to_resize(addr, old_len, new_len, &charged);
        if (IS_ERR(vma)) {
@@ -399,11 +428,8 @@ unsigned long do_mremap(unsigned long addr,
        }
 
        /* old_len exactly to the end of the area..
-        * And we're not relocating the area.
         */
-       if (old_len == vma->vm_end - addr &&
-           !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
-           (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
+       if (old_len == vma->vm_end - addr) {
                unsigned long max_addr = TASK_SIZE;
                if (vma->vm_next)
                        max_addr = vma->vm_next->vm_start;
@@ -432,22 +458,20 @@ unsigned long do_mremap(unsigned long addr,
         */
        ret = -ENOMEM;
        if (flags & MREMAP_MAYMOVE) {
-               if (!(flags & MREMAP_FIXED)) {
-                       unsigned long map_flags = 0;
-                       if (vma->vm_flags & VM_MAYSHARE)
-                               map_flags |= MAP_SHARED;
-
-                       new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
-                                               vma->vm_pgoff, map_flags);
-                       if (new_addr & ~PAGE_MASK) {
-                               ret = new_addr;
-                               goto out;
-                       }
-
-                       ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
-                       if (ret)
-                               goto out;
+               unsigned long map_flags = 0;
+               if (vma->vm_flags & VM_MAYSHARE)
+                       map_flags |= MAP_SHARED;
+
+               new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
+                                       vma->vm_pgoff, map_flags);
+               if (new_addr & ~PAGE_MASK) {
+                       ret = new_addr;
+                       goto out;
                }
+
+               ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
+               if (ret)
+                       goto out;
                ret = move_vma(vma, addr, old_len, new_len, new_addr);
        }
 out: