# \[PATCH 02/12\] container quota: lock/unlock mount namespace when performing quotactl.

- From: \<hidden\>
- Date: 2012-05-30 14:58:56 
- List: linux-ext4
- Page: https://ratatoskr.run/linux-ext4/2012/05/64637
- Thread: https://ratatoskr.run/cgroups/2012/05/64637/t.md

```text
Introduce two functions to lock/unlock a particular mount namespace
when container quota operations is performed.

Signed-off-by: Jie Liu <redacted>
---
 fs/namespace.c                |   17 +++++++++++++++++
 include/linux/mnt_namespace.h |   13 +++++++++++++
 2 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index e608199..8823ba8 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2633,3 +2633,20 @@ bool our_mnt(struct vfsmount *mnt)
 {
 	return check_mnt(real_mount(mnt));
 }
+
+/*
+ * Lock the mount namespace when performing a particular container
+ * disk quotactl operation, especially to protect removing it.
+ */
+void lock_mnt_ns(struct mnt_namespace *ns)
+{
+	down_write(&namespace_sem);
+}
+
+/*
+ * Unlock the mount namespace after quotactl on that was done.
+ */
+void unlock_mnt_ns(struct mnt_namespace *ns)
+{
+	up_write(&namespace_sem);
+}
diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h
index 5a8e390..ff72ed5 100644
--- a/include/linux/mnt_namespace.h
+++ b/include/linux/mnt_namespace.h
@@ -9,6 +9,19 @@ extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,
 		struct fs_struct *);
 extern void put_mnt_ns(struct mnt_namespace *ns);
 
+#ifdef CONFIG_NS_QUOTA
+extern void lock_mnt_ns(struct mnt_namespace *);
+extern void unlock_mnt_ns(struct mnt_namespace *);
+#else
+void lock_mnt_ns(struct mnt_namespace *)
+{
+}
+
+void unlock_mnt_ns(struct mnt_namespace *)
+{
+}
+#endif
+
 extern const struct file_operations proc_mounts_operations;
 extern const struct file_operations proc_mountinfo_operations;
 extern const struct file_operations proc_mountstats_operations;
-- 
1.7.9
```