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Commit e8686772 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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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: default avatarOleg 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 077bf22b

mm/mmap.c

+5 −9
Original line number Diff line number Diff line
@@ -1479,11 +1479,9 @@ 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_inode(file) : NULL;



	/* Check against address space limit. */

	if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
@@ -1552,7 +1550,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr, 
			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 @@ unsigned long mmap_region(struct file *file, unsigned long addr, 
	}



	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 @@ unsigned long mmap_region(struct file *file, unsigned long addr, 
	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);