NFSv2/v3: Fix error handling in nfs_atomic_open_v23()

When nfs_do_create() returns an EEXIST error, it means that a regular
file could not be created. That could mean that a symlink needs to be
resolved. If that's the case, a lookup needs to be kicked off.

Reported-by: Stephen Abbene <sabbene87@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=220710
Fixes: 7c6c524 ("NFS: add atomic_open for NFSv3 to handle O_TRUNC correctly.")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

Author: Trond Myklebust

fs/nfs/dir.c

@@ -2268,11 +2268,12 @@ int nfs_atomic_open_v23(struct inode *dir, struct dentry *dentry,
 		return -ENAMETOOLONG;
 
 	if (open_flags & O_CREAT) {
-		file->f_mode |= FMODE_CREATED;
 		error = nfs_do_create(dir, dentry, mode, open_flags);
-		if (error)
+		if (!error) {
+			file->f_mode |= FMODE_CREATED;
+			return finish_open(file, dentry, NULL);
+		} else if (error != -EEXIST || open_flags & O_EXCL)
 			return error;
-		return finish_open(file, dentry, NULL);
 	}
 	if (d_in_lookup(dentry)) {
 		/* The only flags nfs_lookup considers are