summaryrefslogtreecommitdiff
path: root/fs/aufs/loop.c
diff options
context:
space:
mode:
Diffstat (limited to 'fs/aufs/loop.c')
-rw-r--r--fs/aufs/loop.c145
1 files changed, 145 insertions, 0 deletions
diff --git a/fs/aufs/loop.c b/fs/aufs/loop.c
new file mode 100644
index 000000000..677568445
--- /dev/null
+++ b/fs/aufs/loop.c
@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2005-2015 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);
+ 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;
+
+ AuDebugOn(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)
+{
+ symbol_put(loop_backing_file);
+ kfree(au_warn_loopback_array);
+}