LWN: Comments on "Freezing filesystems and containers"

Freezing filesystems and containers

roc — 2009-01-23T10:14:26+00:00

Currently it's winter up north and summer down here. On this planet anyway.

Freezing filesystems and containers

jake — 2008-06-26T14:58:07+00:00

I plead lack of coffee for the previous comment.  Existing binaries will still work with the
changes made is your point.  And that's why the compatibility of the argument value needs to
be maintained.

jake

Freezing filesystems and containers

jake — 2008-06-26T14:21:00+00:00

I guess I did misunderstand, thanks for the correction!  So, XFS_IOC_FREEZE and THAW still
exist in the user space headers?  So applications that use them don't have to change at all?

jake

Freezing filesystems and containers

dgc — 2008-06-26T14:15:00+00:00

Jake,

I think you misunderstood what we did with the XFS ioctls
and FIFREEZE/FITHAW. The XFS ioctls only got "removed" because
FIFREEZE/FITHAW replace them by having the same value as
the XFS ioctls. i.e.:

+#define FIFREEZE       _IOWR('X', 119, int)    /* Freeze */
+#define FITHAW         _IOWR('X', 120, int)    /* Thaw */

-#define XFS_IOC_FREEZE              _IOWR('X', 119, int)
-#define XFS_IOC_THAW                _IOWR('X', 120, int)

Hence any application using the XFS ioctls will continue to
work; they'll just vector through the FIFREEZE/FITHAW
code instead of directly into XFS. That means special handling
of the known arg values to the XFS ioctls needs to remain, despite
it appearing like it's a different interface.