[PATCH v3 16/21] ovl: narrow locking on ovl_remove_and_whiteout()

[NeilBrown <neil@brown.name>]

This code:
  performs a lookup_upper
  creates a whiteout object
  renames the whiteout over the result of the lookup

The create and the rename must be locked separately for proposed
directory locking changes.  This patch takes a first step of moving the
lookup out of the locked region.  A subsequent patch will separate the
create from the rename.

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/overlayfs/dir.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index e81be60f1125..340f8679b6e7 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -770,15 +770,11 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
 			goto out;
 	}
 
-	err = ovl_lock_rename_workdir(workdir, NULL, upperdir, NULL);
-	if (err)
-		goto out_dput;
-
-	upper = ovl_lookup_upper(ofs, dentry->d_name.name, upperdir,
-				 dentry->d_name.len);
+	upper = ovl_lookup_upper_unlocked(ofs, dentry->d_name.name, upperdir,
+					  dentry->d_name.len);
 	err = PTR_ERR(upper);
 	if (IS_ERR(upper))
-		goto out_unlock;
+		goto out_dput;
 
 	err = -ESTALE;
 	if ((opaquedir && upper != opaquedir) ||
@@ -787,17 +783,18 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
 		goto out_dput_upper;
 	}
 
-	err = ovl_cleanup_and_whiteout(ofs, upperdir, upper);
+	err = ovl_lock_rename_workdir(workdir, NULL, upperdir, upper);
 	if (err)
-		goto out_d_drop;
+		goto out_dput_upper;
+
+	err = ovl_cleanup_and_whiteout(ofs, upperdir, upper);
+	if (!err)
+		ovl_dir_modified(dentry->d_parent, true);
 
-	ovl_dir_modified(dentry->d_parent, true);
-out_d_drop:
 	d_drop(dentry);
+	unlock_rename(workdir, upperdir);
 out_dput_upper:
 	dput(upper);
-out_unlock:
-	unlock_rename(workdir, upperdir);
 out_dput:
 	dput(opaquedir);
 out:
-- 
2.49.0