On Mon, Oct 27, 2014 at 02:39:21PM +0000, David Howells wrote:
> Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>
> > Uh-oh. We changed nesting late in the cycle and I didn't retest with lockdep.
> >
> > And it's actually harmless, but AFAICS needs another level of nesting between
> > I_MUTEX_CHILD and I_MUTEX_NORMAL.
>
> In an overlay directory that shadows an empty lower directory, say
> /mnt/a/empty102, do:
>
> touch /mnt/a/empty102/x
> unlink /mnt/a/empty102/x
> rmdir /mnt/a/empty102
Yes, following (untested) patch should fix it:
Thanks,
Miklos
diff --git a/fs/namei.c b/fs/namei.c
index 42df664e95e5..922f27068c4c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2497,7 +2497,7 @@ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
}
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
- mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
+ mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT2);
return NULL;
}
EXPORT_SYMBOL(lock_rename);
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 910553f37aca..de77b5c62d72 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -569,7 +569,7 @@ void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list)
{
struct ovl_cache_entry *p;
- mutex_lock_nested(&upper->d_inode->i_mutex, I_MUTEX_PARENT);
+ mutex_lock_nested(&upper->d_inode->i_mutex, I_MUTEX_CHILD);
list_for_each_entry(p, list, l_node) {
struct dentry *dentry;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4e41a4a331bb..01036262095f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -639,11 +639,13 @@ static inline int inode_unhashed(struct inode *inode)
* 2: child/target
* 3: xattr
* 4: second non-directory
- * The last is for certain operations (such as rename) which lock two
+ * 5: second parent (when locking independent directories in rename)
+ *
+ * I_MUTEX_NONDIR2 is for certain operations (such as rename) which lock two
* non-directories at once.
*
* The locking order between these classes is
- * parent -> child -> normal -> xattr -> second non-directory
+ * parent[2] -> child -> grandchild -> normal -> xattr -> second non-directory
*/
enum inode_i_mutex_lock_class
{
@@ -651,7 +653,8 @@ enum inode_i_mutex_lock_class
I_MUTEX_PARENT,
I_MUTEX_CHILD,
I_MUTEX_XATTR,
- I_MUTEX_NONDIR2
+ I_MUTEX_NONDIR2,
+ I_MUTEX_PARENT2,
};
void lock_two_nondirectories(struct inode *, struct inode*);
--
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