[PATCH 15/20] ovl: narrow locking on ovl_remove_and_whiteout()

[NeilBrown <neil@brown.name>]

Normally it is ok to include a lookup with the subsequent operation on
the result.  However in this case ovl_cleanup_and_whiteout() already
(potentially) creates a whiteout inode so we need separate locking.

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/overlayfs/dir.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index d01e83f9d800..8580cd5c61e4 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -769,15 +769,11 @@ 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) ||
@@ -786,6 +782,10 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
 		goto out_dput_upper;
 	}
 
+	err = ovl_lock_rename_workdir(workdir, NULL, upperdir, upper);
+	if (err)
+		goto out_dput_upper;
+
 	err = ovl_cleanup_and_whiteout(ofs, upperdir, upper);
 	if (err)
 		goto out_d_drop;
@@ -793,10 +793,9 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
 	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