/usr/src/aufs-4.9+20161219/fs/aufs/loop.c is in aufs-dkms 4.9+20161219-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 | /*
* Copyright (C) 2005-2016 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, see <http://www.gnu.org/licenses/>.
*/
/*
* support for loopback block device as a branch
*/
#include "aufs.h"
/* added into drivers/block/loop.c */
static struct file *(*backing_file_func)(struct super_block *sb);
/*
* 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 file *backing_file;
if (unlikely(!backing_file_func)) {
/* don't load "loop" module here */
backing_file_func = symbol_get(loop_backing_file);
if (unlikely(!backing_file_func))
/* "loop" module is not loaded */
return 0;
}
h_sb = h_adding->d_sb;
backing_file = backing_file_func(h_sb);
if (!backing_file)
return 0;
h_adding = backing_file->f_path.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;
char c, comm[sizeof(tsk->comm)];
ret = 0;
if (tsk->flags & PF_KTHREAD) {
get_task_comm(comm, tsk);
c = comm[4];
ret = ('0' <= c && c <= '9'
&& !strncmp(comm, "loop", 4));
}
return ret;
}
/* ---------------------------------------------------------------------- */
#define au_warn_loopback_step 16
static int au_warn_loopback_nelem = au_warn_loopback_step;
static unsigned long *au_warn_loopback_array;
void au_warn_loopback(struct super_block *h_sb)
{
int i, new_nelem;
unsigned long *a, magic;
static DEFINE_SPINLOCK(spin);
magic = h_sb->s_magic;
spin_lock(&spin);
a = au_warn_loopback_array;
for (i = 0; i < au_warn_loopback_nelem && *a; i++)
if (a[i] == magic) {
spin_unlock(&spin);
return;
}
/* h_sb is new to us, print it */
if (i < au_warn_loopback_nelem) {
a[i] = magic;
goto pr;
}
/* expand the array */
new_nelem = au_warn_loopback_nelem + au_warn_loopback_step;
a = au_kzrealloc(au_warn_loopback_array,
au_warn_loopback_nelem * sizeof(unsigned long),
new_nelem * sizeof(unsigned long), GFP_ATOMIC,
/*may_shrink*/0);
if (a) {
au_warn_loopback_nelem = new_nelem;
au_warn_loopback_array = a;
a[i] = magic;
goto pr;
}
spin_unlock(&spin);
AuWarn1("realloc failed, ignored\n");
return;
pr:
spin_unlock(&spin);
pr_warn("you may want to try another patch for loopback file "
"on %s(0x%lx) branch\n", au_sbtype(h_sb), magic);
}
int au_loopback_init(void)
{
int err;
struct super_block *sb __maybe_unused;
BUILD_BUG_ON(sizeof(sb->s_magic) != sizeof(unsigned long));
err = 0;
au_warn_loopback_array = kcalloc(au_warn_loopback_step,
sizeof(unsigned long), GFP_NOFS);
if (unlikely(!au_warn_loopback_array))
err = -ENOMEM;
return err;
}
void au_loopback_fin(void)
{
if (backing_file_func)
symbol_put(loop_backing_file);
au_delayed_kfree(au_warn_loopback_array);
}
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