Bug #38383: compare-and-write skips compare after copyup without object map - rbd - Ceph

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Bug #38383

closed

compare-and-write skips compare after copyup without object map

Added by Ilya Dryomov about 5 years ago. Updated almost 5 years ago.

Status:

Resolved

Priority:

Urgent

Assignee:

Ilya Dryomov

Target version:

% Done:

Source:

Tags:

Backport:

luminous,mimic

Regression:

Severity:

3 - minor

Reviewed:

Affected Versions:

ceph-qa-suite:

Pull request ID:

26519

Crash signature (v1):

Crash signature (v2):

Description

With object map disabled, a copyup turns compare-and-write into an ordinary write. This is because ObjectOperation::cmpext() claims the passed buffer:

... ObjectCompareAndWriteRequest::add_write_ops(), m_cmp_bl is claimed ...
[stat,set-alloc-hint object_size 4194304 write_size 4194304,cmpext 512~96,write 512~512]
... copyup, is_post_copyup_write_required() -> true ...
... ObjectCompareAndWriteRequest::add_write_ops(), m_cmp_bl is empty ...
[stat,set-alloc-hint object_size 4194304 write_size 4194304,cmpext 512~0,write 512~512]

Since there is no data to compare with, nothing is read and cmpext returns success.

This doesn't happen when object map is enabled because we go straight to the copyup step in that case.

Related issues 2 (0 open — 2 closed)