xfsdump 3.1.1-rc1
xfsdump: Revert dump version bump for 32bit projid fix

commit 1e309da7a4f7e2a2f456bf6b7cea4c5f1181cd36 fixed xfsdump to
properly save & restore the top 16 bits of a 32-bit projid, which
otherwise was being dropped (and restored as 0) in older xfsdump.

The original thought was to bump the dump version, so that we know
whether the dump (may) have the top 16 bits filled in.  In practice
this would prevent older restores from restoring newer dumps, and
losing the top 16 bits contained in these newer dumps.

However, in hindsight this appears to be of limited value.  I
propose that the dump version change is unuseful/unwanted for a
couple reasons:

* There is no actual dump *format* change; the structure size
  is the same, and the top 16 bits were properly zeroed before; old
  restores will read these fixed dumps without problems and without
  restoring garbage.  IOW, they will behave exactly as buggily as
  they did before.  And worst case, if a dump containing the top 16
  bits is mangled by an old restore, this can be easily remedied by
  simply re-restoring with updated userspace.

* We have no reliable method to know whether 32 bit project IDs are
  in use; the feature flag was not added to the GEOM call at the time
  of implementation.  Therefore we cannot reliably bump to V4 only
  for projid32bit filesystems, and we cannot restrict V4 restores
  only to projid32bit filesystems.  So the dump version is not
  useful for feature cross-checking purposes.

I spoke with wkendall via email, and although he may not have given
it the most scrutiny (having moved on from xfsdump-land), he also
felt that a version dump may not be warranted.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

2 files changed