mmap_region: cleanup the final vma_merge() related code

It is not easy to actually understand the "if (!file || !vma_merge())"
code, turn it into "if (file && vma_merge())".  This makes immediately
obvious that the subsequent "if (file)" is superfluous.

As Hugh Dickins pointed out, we can also factor out the ->i_writecount
corrections, and add a small comment about that.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index a32d28c..6aaf657 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1068,7 +1068,6 @@ int vma_wants_writenotify(struct vm_area_struct *vma)
                mapping_cap_account_dirty(vma->vm_file->f_mapping);
 }
 
-
 unsigned long mmap_region(struct file *file, unsigned long addr,
                          unsigned long len, unsigned long flags,
                          unsigned int vm_flags, unsigned long pgoff,
@@ -1181,22 +1180,20 @@ munmap_back:
        if (vma_wants_writenotify(vma))
                vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
 
-       if (!file || !vma_merge(mm, prev, addr, vma->vm_end,
+       if (file && vma_merge(mm, prev, addr, vma->vm_end,
                        vma->vm_flags, NULL, file, pgoff, vma_policy(vma))) {
-               file = vma->vm_file;
-               vma_link(mm, vma, prev, rb_link, rb_parent);
-               if (correct_wcount)
-                       atomic_inc(&inode->i_writecount);
-       } else {
-               if (file) {
-                       if (correct_wcount)
-                               atomic_inc(&inode->i_writecount);
-                       fput(file);
-               }
                mpol_free(vma_policy(vma));
                kmem_cache_free(vm_area_cachep, vma);
+               fput(file);
+       } else {
+               vma_link(mm, vma, prev, rb_link, rb_parent);
+               file = vma->vm_file;
        }
-out:   
+
+       /* Once vma denies write, undo our temporary denial count */
+       if (correct_wcount)
+               atomic_inc(&inode->i_writecount);
+out:
        mm->total_vm += len >> PAGE_SHIFT;
        vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
        if (vm_flags & VM_LOCKED) {