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/*
* Copyright (C) 2005-2010 Junjiro R. Okajima
*
* This program, aufs is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*
* support for loopback block device as a branch
*/
#include <linux/loop.h>
#include "aufs.h"
/*
* test if two lower dentries have overlapping branches.
*/
int au_test_loopback_overlap(struct super_block *sb, struct dentry *h_adding)
{
struct super_block *h_sb;
struct loop_device *l;
h_sb = h_adding->d_sb;
if (MAJOR(h_sb->s_dev) != LOOP_MAJOR)
return 0;
l = h_sb->s_bdev->bd_disk->private_data;
h_adding = l->lo_backing_file->f_dentry;
/*
* h_adding can be local NFS.
* in this case aufs cannot detect the loop.
*/
if (unlikely(h_adding->d_sb == sb))
return 1;
return !!au_test_subdir(h_adding, sb->s_root);
}
/* true if a kernel thread named 'loop[0-9].*' accesses a file */
int au_test_loopback_kthread(void)
{
int ret;
struct task_struct *tsk = current;
ret = 0;
if (tsk->flags & PF_KTHREAD) {
const char c = tsk->comm[4];
ret = ('0' <= c && c <= '9'
&& !strncmp(tsk->comm, "loop", 4));
}
return ret;
}
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