Currently we are taking mount_writer; what that function needs is
either mount_locked_reader (we are not changing anything, we just
want to iterate through the subtree) or namespace_shared and
a reference held by caller on the root of subtree - that's also
enough to stabilize the topology.
The thing is, all callers are already holding at least namespace_shared
as well as a reference to the root of subtree.
Let's make the callers provide locking warranties - don't mess with
mount_lock in check_for_nsfs_mounts() itself and document the locking
requirements.
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index a5d37b97088f..59948cbf9c47 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2402,21 +2402,15 @@ bool has_locked_children(struct mount *mnt, struct dentry *dentry)
* specified subtree. Such references can act as pins for mount namespaces
* that aren't checked by the mount-cycle checking code, thereby allowing
* cycles to be made.
+ *
+ * locks: mount_locked_reader || namespace_shared && pinned(subtree)
*/
static bool check_for_nsfs_mounts(struct mount *subtree)
{
- struct mount *p;
- bool ret = false;
-
- lock_mount_hash();
- for (p = subtree; p; p = next_mnt(p, subtree))
+ for (struct mount *p = subtree; p; p = next_mnt(p, subtree))
if (mnt_ns_loop(p->mnt.mnt_root))
- goto out;
-
- ret = true;
-out:
- unlock_mount_hash();
- return ret;
+ return false;
+ return true;
}
/**
--
2.47.2
