On 10/22/12 5:31 PM, Dave Chinner wrote: > On Mon, Oct 22, 2012 at 03:24:16PM -0500, Eric Sandeen wrote: >> 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. > > Seems reasonable. Definitely solves most of the nasty problems > you've been juggling caused by a version bump and 32bit projid > detection. Do we have an xfstest that verifies these assumptions are > valid? I'll whip up a test that tests what happens when restoring a dump w/ all 32 bits to a filesystem w/o the feature. I'm not sure testing a restoration of an "old" dump to a 32-bit projid is too useful, it really just tests that the zeroed bits in the old dump image stay zeroed. -Eric > Cheers, > > Dave. > _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
