ovl: narrow locking in ovl_workdir_create()

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>
Link: https://lore.kernel.org/20250716004725.1206467-13-neil@brown.name
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 2e6b25bde83f6cd2a83d746e27b7865bdbf6bcf9..cb2551a155d8e6c2c195e4b63ce8cfa8529f3b9f 100644 (file)
--- 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 +311,28 @@ retry:
 
                if (work->d_inode) {
                        err = -EEXIST;
+                       inode_unlock(dir);
                        if (retried)
                                goto out_dput;
 
                        if (persist)
-                               goto out_unlock;
+                               return work;
 
                        retried = true;
-                       err = ovl_workdir_cleanup(ofs, dir, mnt, work, 0);
-                       dput(work);
-                       if (err == -EINVAL) {
-                               work = ERR_PTR(err);
-                               goto out_unlock;
+                       err = ovl_parent_lock(ofs->workbasedir, work);
+                       if (!err) {
+                               err = ovl_workdir_cleanup(ofs, dir, mnt, work, 0);
+                               ovl_parent_unlock(ofs->workbasedir);
                        }
+                       dput(work);
+                       if (err == -EINVAL)
+                               return ERR_PTR(err);
+
                        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 +370,10 @@ retry:
                if (err)
                        goto out_dput;
        } else {
+               inode_unlock(dir);
                err = PTR_ERR(work);
                goto out_err;
        }
-out_unlock:
-       inode_unlock(dir);
        return work;
 
 out_dput:
@@ -377,8 +381,7 @@ out_dput:
 out_err:
        pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
                ofs->config.workdir, name, -err);
-       work = NULL;
-       goto out_unlock;
+       return NULL;
 }
 
 static int ovl_check_namelen(const struct path *path, struct ovl_fs *ofs,