[linux-cifs-client] [PATCH 3/7] [CIFS] silently ignore ownership changes unless unix extensions are enabled

[Jeff Layton]

CIFS currently allows you to change the ownership of a file, but unless
unix extensions are enabled this change is not passed off to the server.

Have CIFS silently ignore ownership changes that can't be persistently
stored on the server. We could return an error here (-EOPNOTSUPP or
something), but this is how most disk-based windows filesystems on
behave on Linux (e.g. VFAT, NTFS, etc).

With cifsacl support and proper Windows to Unix idmapping support, we
may be able to do this in the future. Until then, there's no point in
just changing the inode in memory since it can be flushed out under
memory pressure.

Signed-off-by: Jeff Layton <jlayton at redhat.com>
---
 fs/cifs/inode.c |   26 +++++++++++++++++++-------
 1 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index ed53b33..5a2a503 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1525,13 +1525,25 @@ int cifs_setattr(struct dentry *direntry, struct iattr *attrs)
 		} else
 			goto cifs_setattr_exit;
 	}
-	if (attrs->ia_valid & ATTR_UID) {
-		cFYI(1, ("UID changed to %d", attrs->ia_uid));
-		uid = attrs->ia_uid;
-	}
-	if (attrs->ia_valid & ATTR_GID) {
-		cFYI(1, ("GID changed to %d", attrs->ia_gid));
-		gid = attrs->ia_gid;
+
+	/*
+	 * Without unix extensions we can't send ownership changes to the
+	 * server, so silently ignore them. This is consistent with how
+	 * local DOS/Windows filesystems behave (VFAT, NTFS, etc). With
+	 * CIFSACL support + proper Windows to Unix idmapping, we may be
+	 * able to support this in the future.
+	 */
+	if (!pTcon->unix_ext) {
+		attrs->ia_valid &= ~(ATTR_UID | ATTR_GID);
+	} else {
+		if (attrs->ia_valid & ATTR_UID) {
+			cFYI(1, ("UID changed to %d", attrs->ia_uid));
+			uid = attrs->ia_uid;
+		}
+		if (attrs->ia_valid & ATTR_GID) {
+			cFYI(1, ("GID changed to %d", attrs->ia_gid));
+			gid = attrs->ia_gid;
+		}
 	}
 
 	time_buf.Attributes = 0;
-- 
1.5.3.6