2 * Copyright (C) 2005-2012 Junjiro R. Okajima
4 * This program, aufs is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 * support for loopback block device as a branch
23 #include <linux/loop.h>
27 * test if two lower dentries have overlapping branches.
29 int au_test_loopback_overlap(struct super_block *sb, struct dentry *h_adding)
31 struct super_block *h_sb;
32 struct loop_device *l;
34 h_sb = h_adding->d_sb;
35 if (MAJOR(h_sb->s_dev) != LOOP_MAJOR)
38 l = h_sb->s_bdev->bd_disk->private_data;
39 h_adding = l->lo_backing_file->f_dentry;
41 * h_adding can be local NFS.
42 * in this case aufs cannot detect the loop.
44 if (unlikely(h_adding->d_sb == sb))
46 return !!au_test_subdir(h_adding, sb->s_root);
49 /* true if a kernel thread named 'loop[0-9].*' accesses a file */
50 int au_test_loopback_kthread(void)
53 struct task_struct *tsk = current;
56 if (tsk->flags & PF_KTHREAD) {
57 const char c = tsk->comm[4];
58 ret = ('0' <= c && c <= '9'
59 && !strncmp(tsk->comm, "loop", 4));
65 /* ---------------------------------------------------------------------- */
67 #define au_warn_loopback_step 16
68 static int au_warn_loopback_nelem = au_warn_loopback_step;
69 static unsigned long *au_warn_loopback_array;
71 void au_warn_loopback(struct super_block *h_sb)
74 unsigned long *a, magic;
75 static DEFINE_SPINLOCK(spin);
77 magic = h_sb->s_magic;
79 a = au_warn_loopback_array;
80 for (i = 0; i < au_warn_loopback_nelem && *a; i++)
86 /* h_sb is new to us, print it */
87 if (i < au_warn_loopback_nelem) {
92 /* expand the array */
93 new_nelem = au_warn_loopback_nelem + au_warn_loopback_step;
94 a = au_kzrealloc(au_warn_loopback_array,
95 au_warn_loopback_nelem * sizeof(unsigned long),
96 new_nelem * sizeof(unsigned long), GFP_ATOMIC);
98 au_warn_loopback_nelem = new_nelem;
99 au_warn_loopback_array = a;
105 AuWarn1("realloc failed, ignored\n");
110 pr_warning("you may want to try another patch for loopback file "
111 "on %s(0x%lx) branch\n", au_sbtype(h_sb), magic);
114 int au_loopback_init(void)
117 struct super_block *sb __maybe_unused;
119 AuDebugOn(sizeof(sb->s_magic) != sizeof(unsigned long));
122 au_warn_loopback_array = kcalloc(au_warn_loopback_step,
123 sizeof(unsigned long), GFP_NOFS);
124 if (unlikely(!au_warn_loopback_array))
130 void au_loopback_fin(void)
132 kfree(au_warn_loopback_array);