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mm: mmap_region: kill correct_wcount/inode, use allow_write_access()

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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().

Change-Id: I80d3674ce40fb97a80b128ea63edc86ca1770d20
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>
This commit is contained in:
Oleg Nesterov 2013-09-11 14:20:20 -07:00 committed by surblazer
parent 788c56f8df
commit d079aac846
1 changed files with 5 additions and 9 deletions
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14
mm/mmap.c
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@ -1290,11 +1290,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
{
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->f_path.dentry->d_inode : NULL;
/* Check against address space limit. */
if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
@ -1383,7 +1381,6 @@ munmap_back:
error = deny_write_access(file);
if (error)
goto free_vma;
correct_wcount = 1;
}
vma->vm_file = file;
get_file(file);
@ -1425,11 +1422,10 @@ munmap_back:
}
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);
@ -1443,8 +1439,8 @@ out:
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);