On Tue, 2007-01-09 at 13:26 +0100, Jan Kara wrote: > Yes, making fs readonly at VFS level would not work for already opened > files. But you if you create new union, you could lock down the > filesystems you are unioning (via s_umount semaphore), go through lists > of all open fd's on those filesystems and check whether they are open > for write or not. If some fd is open for writing, you simply fail to > create the union (and it's upto user to solve the problem). Otherwise > you mark filesystems as RO and safely proceed with creating the union. > I guess you must have come up with this solution. So what is the problem > with it? Aside from the fact that this is racy (s_umount doesn't protect you against a process opening a new file while you are busy running through the open fds to see if you can reset the MS_RDONLY flag) all you will have achieved is ensure that your client won't write to the file. You will still be able to Oops. Trond - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html