On Tue, Mar 14, 2023 at 7:25 AM Darrick J. Wong <djwong@xxxxxxxxxx> wrote: > > On Tue, Mar 14, 2023 at 07:11:56AM +0200, Amir Goldstein wrote: > > On Tue, Mar 14, 2023 at 6:25 AM Catherine Hoang > > <catherine.hoang@xxxxxxxxxx> wrote: > > > > > > Implement internal freeze/thaw functions and prevent other threads from changing > > > the freeze level by adding a new SB_FREEZE_ECLUSIVE level. This is required to > > > > This looks troubling in several ways: > > - Layering violation > > - Duplication of subtle vfs code > > > > > prevent concurrent transactions while we are updating the uuid. > > > > > > > Wouldn't it be easier to hold s_umount while updating the uuid? > > Why? Userspace holds an open file descriptor, the fs won't get > unmounted. "Implement internal freeze/thaw functions and prevent other threads from changing the freeze level..." holding s_umount prevents changing freeze levels. The special thing about the frozen state is that userspace is allowed to leave the fs frozen without holding any open fd, but because there is no such requirement from SET_FSUUID I don't understand the need for a new freeze level. Thanks, Amir.
