Note: This bug is displayed in read-only format because
the product is no longer active in Red Hat Bugzilla.
RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
DescriptionAlasdair Kergon
2005-11-14 18:17:05 UTC
The snapshot chunk size must not exceed 512K or else bvec_alloc_bs()
will fail with 4K pages, and snapshot metadata needs to be usable
regardless of page size.
dm-snapshot-chunksize-fix.patch
I can't think of a clean way to do this properly. Let's just check we detect
incompatible snapshots and don't attempt to activate them. Quick investigation
and see if anything simple needs changing.
I tested big snapshots (8M and 16M) on upstream, RHEL 4 and RHEL 5 and they just
work. (I remove the test from lvcreate)
If they didn't, it would be quite trivial to make them work (code for breaking
the request up into pieces is already in kcopyd, so it could be just used
properly).
Comment 19RHEL Program Management
2009-02-05 23:32:07 UTC
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release. Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release. This request is not yet committed for
inclusion.
So in summary, I believe the original problem - the crash that occurred when creating a snapshot with a large chunksize on one architecture and later using it on an architecture with a different page size - has been fixed upstream (and therefore in RHEL6). Mikulas, if you agree, we should now close this bug.
Yes, it is fixed in upstream 2.6.29 and above, so it will be fixed in RHEL 6.0 as well.
Some times ago I tested chunk sizes bigger than 1M and they work. So I'm closing this bug.
BTW. that crash with chunk_size < page_size is a separate issue, and it was already fixed in upstream and in RHEL 5.