mm: mmap_region: kill correct_wcount/inode, use allow_write_access()
correct_wcount and inode in mmap_region() just complicate the code. This
boolean was needed previously, when deny_write_access() was called before
vma_merge(), now we can simply check VM_DENYWRITE and do
allow_write_access() if it is set.
allow_write_access() checks file != NULL, so this is safe even if it was
possible to use VM_DENYWRITE && !file. Just we need to ensure we use the
same file which was deny_write_access()'ed, so the patch also moves "file
= vma->vm_file" down after allow_write_access().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Colin Cross <ccross@android.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.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 1e7a3ea..13926a5 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1479,11 +1479,9 @@
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *prev;
- int correct_wcount = 0;
int error;
struct rb_node **rb_link, *rb_parent;
unsigned long charged = 0;
- struct inode *inode = file ? file_inode(file) : NULL;
/* Check against address space limit. */
if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
@@ -1552,7 +1550,6 @@
error = deny_write_access(file);
if (error)
goto free_vma;
- correct_wcount = 1;
}
vma->vm_file = get_file(file);
error = file->f_op->mmap(file, vma);
@@ -1593,11 +1590,10 @@
}
vma_link(mm, vma, prev, rb_link, rb_parent);
- file = vma->vm_file;
-
/* Once vma denies write, undo our temporary denial count */
- if (correct_wcount)
- atomic_inc(&inode->i_writecount);
+ if (vm_flags & VM_DENYWRITE)
+ allow_write_access(file);
+ file = vma->vm_file;
out:
perf_event_mmap(vma);
@@ -1616,8 +1612,8 @@
return addr;
unmap_and_free_vma:
- if (correct_wcount)
- atomic_inc(&inode->i_writecount);
+ if (vm_flags & VM_DENYWRITE)
+ allow_write_access(file);
vma->vm_file = NULL;
fput(file);