[PATCH] udf: fix uid/gid options and add uid/gid=ignore and forget options

As Pekka Enberg pointed out, with the if still following the else, you can
still get a null uid written to the disk if you specify a default uid= without
uid=forget.  In other words, if the desktop user is uid=1000 and the mount
option uid=1000 is given ( which is done on ubuntu automatically and probably
other distributions that use hal ), then if any other user besides uid 1000
owns a file then a 0 will be written to the media as the owning uid instead.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/filesystems/udf.txt

@@ -26,6 +26,20 @@ The following mount options are supported:
 	nostrict	Unset strict conformance
 	iocharset=	Set the NLS character set
 
+The uid= and gid= options need a bit more explaining.  They will accept a
+decimal numeric value which will be used as the default ID for that mount.
+They will also accept the string "ignore" and "forget".  For files on the disk
+that are owned by nobody ( -1 ), they will instead look as if they are owned
+by the default ID.  The ignore option causes the default ID to override all
+IDs on the disk, not just -1.  The forget option causes all IDs to be written
+to disk as -1, so when the media is later remounted, they will appear to be
+owned by whatever default ID it is mounted with at that time.
+
+For typical desktop use of removable media, you should set the ID to that
+of the interactively logged on user, and also specify both the forget and
+ignore options.  This way the interactive user will always see the files
+on the disk as belonging to him.
+
 The remaining are for debugging and disaster recovery:
 
 	novrs		Skip volume sequence recognition 

fs/udf/inode.c

@@ -1341,13 +1341,11 @@ udf_update_inode(struct inode *inode, int do_sync)
 
 	if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_UID_FORGET))
 		fe->uid = cpu_to_le32(-1);
-	else if (inode->i_uid != UDF_SB(inode->i_sb)->s_uid)
-		fe->uid = cpu_to_le32(inode->i_uid);
+	else fe->uid = cpu_to_le32(inode->i_uid);
 
 	if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_GID_FORGET))
 		fe->gid = cpu_to_le32(-1);
-	else if (inode->i_gid != UDF_SB(inode->i_sb)->s_gid)
-		fe->gid = cpu_to_le32(inode->i_gid);
+	else fe->gid = cpu_to_le32(inode->i_gid);
 
 	udfperms =	((inode->i_mode & S_IRWXO)     ) |
 			((inode->i_mode & S_IRWXG) << 2) |