[PATCH 11/20] ovl: narrow locking in ovl_workdir_create()

[NeilBrown <neil@brown.name>]

In ovl_workdir_create() don't hold the dir lock for the whole time, but
only take it when needed.

It now gets taken separately for ovl_workdir_cleanup().  A subsequent
patch will move the locking into that function.

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/overlayfs/super.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 9cce3251dd83..239ae1946edf 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -299,8 +299,8 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 	int err;
 	bool retried = false;
 
-	inode_lock_nested(dir, I_MUTEX_PARENT);
 retry:
+	inode_lock_nested(dir, I_MUTEX_PARENT);
 	work = ovl_lookup_upper(ofs, name, ofs->workbasedir, strlen(name));
 
 	if (!IS_ERR(work)) {
@@ -311,23 +311,27 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 
 		if (work->d_inode) {
 			err = -EEXIST;
+			inode_unlock(dir);
 			if (retried)
 				goto out_dput;
 
 			if (persist)
-				goto out_unlock;
+				goto out;
 
 			retried = true;
+			inode_lock_nested(dir, I_MUTEX_PARENT);
 			err = ovl_workdir_cleanup(ofs, dir, mnt, work, 0);
+			inode_unlock(dir);
 			dput(work);
 			if (err == -EINVAL) {
 				work = ERR_PTR(err);
-				goto out_unlock;
+				goto out;
 			}
 			goto retry;
 		}
 
 		work = ovl_do_mkdir(ofs, dir, work, attr.ia_mode);
+		inode_unlock(dir);
 		err = PTR_ERR(work);
 		if (IS_ERR(work))
 			goto out_err;
@@ -365,11 +369,11 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 		if (err)
 			goto out_dput;
 	} else {
+		inode_unlock(dir);
 		err = PTR_ERR(work);
 		goto out_err;
 	}
-out_unlock:
-	inode_unlock(dir);
+out:
 	return work;
 
 out_dput:
@@ -378,7 +382,7 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 	pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
 		ofs->config.workdir, name, -err);
 	work = NULL;
-	goto out_unlock;
+	goto out;
 }
 
 static int ovl_check_namelen(const struct path *path, struct ovl_fs *ofs,
-- 
2.49.0