Bug #64063: rbd-nbd: incorrect device size immediately after mapping images using ioctl - rbd - Ceph

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Bug #64063

closed

rbd-nbd: incorrect device size immediately after mapping images using ioctl

Added by Ramana Raja 4 months ago. Updated 3 months ago.

Status:

Resolved

Priority:

Normal

Assignee:

Ramana Raja

Target version:

% Done:

Source:

Tags:

Backport:

Regression:

Severity:

3 - minor

Reviewed:

Affected Versions:

ceph-qa-suite:

Pull request ID:

55234

Crash signature (v1):

Crash signature (v2):

Description

Mapped rbd images/snapshots to nbd devices using ioctl method, which is currently the default method of mapping using rbd-nbd. Checked the device size and the MD5 checksum of the device immediately after the mapping. The device size and the MD5 checksum were zero bytes and d41d8cd98f00b204e9800998ecf8427e (MD5 checksum of a zero byte file) respectively. After sleeping for a few seconds, the correct device size and MD5 checksum were reported. It seems like the command to map a rbd image to a nbd device using ioctl method returns before waiting for the device to be ready for use.

However, no such issues were observed when mapping a rbd image to a nbd device using the netlink method.

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Updated by Ilya Dryomov 4 months ago

Unclear if it's worth working around this by waiting internally at this point. I think the action here is to use the netlink method by default, keeping the legacy ioctl method with all of its issues only as a fallback.

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