[PATCH v8 06/12] vfs: lookup_open(): lock the parent as I_MUTEX_PARENT

[Jori Koolstra]

lookup_open() takes the parent directory's i_rwsem with inode_lock(),
that is, in the I_MUTEX_NORMAL class, before creating the last
component. Every other VFS path that locks a directory in order to
create something in it goes through start_dirop() and friends, which
use inode_lock_nested(dir, I_MUTEX_PARENT).

Lock the parent as I_MUTEX_PARENT here too, so that lookup_open()
matches the rest of the VFS before it starts calling ->mkdir(), which
until now was only ever reached with the parent held that way.

No functional change intended.

Signed-off-by: Jori Koolstra <jkoolstra@xxxxxxxxx>
---
 fs/namei.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 8b8e248edfeb..efd0e2e5fbf8 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4483,10 +4483,11 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
 		 * a different error; we'll be dropping this one anyway.
 		 */
 	}
+
 	if (shared_flag)
-		inode_lock_shared(dir_inode);
+		inode_lock_shared_nested(dir_inode, I_MUTEX_PARENT);
 	else
-		inode_lock(dir_inode);
+		inode_lock_nested(dir_inode, I_MUTEX_PARENT);
 
 	if (unlikely(IS_DEADDIR(dir_inode))) {
 		dentry = ERR_PTR(-ENOENT);
-- 
2.56.0