Can ovl_drop_write() be called earlier in ovl_dentry_open()

From: David Howells
Date: Mon Jun 01 2015 - 09:52:35 EST


In ovl_dentry_open(), ovl_drop_write() is called after vfs_open() - but is
this actually necessary? Can't we just drop it post-copyup? After all,
that's all we wanted the write lock for, right?

David
---
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -356,16 +356,14 @@ static int ovl_dentry_open(struct dentry *dentry, struct inode *inode,
err = ovl_copy_up_last(dentry, NULL, true);
else
err = ovl_copy_up(dentry);
+ ovl_drop_write(dentry);
if (err)
- goto out_drop_write;
+ goto out;

ovl_path_upper(dentry, &realpath);
}

err = vfs_open(&realpath, d_backing_inode(realpath.dentry), file, cred);
-out_drop_write:
- if (want_write)
- ovl_drop_write(dentry);
out:
return err;
}
--
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