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Bug 837963

Summary: ext4 gets corrupted when hosting loopback filesystems due to discard
Product: Red Hat Enterprise Linux 7 Reporter: Eric Sandeen <esandeen>
Component: kernelAssignee: Eric Sandeen <esandeen>
Status: CLOSED DUPLICATE QA Contact: Red Hat Kernel QE team <kernel-qe>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.0   
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2012-07-05 23:06:08 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Eric Sandeen 2012-07-05 22:59:19 UTC
When using ext4 as the backing device for a loopback xfs filesystem, it gets corrupted during an xfstests run.

A short reproducer is to configure the test device as xfs, and make the scratch device a 10G loopback filesystem, hosted on ext4.  Then run ./check 167 168

This is due the discards issued by mkfs.xfs during the test, which punches holes in the ext4 file, and ends up corrupting it.  It's fixed upstream by:

commit 5f95d21fb6f2aaa52830e5b7fb405f6c71d3ab85
Author: Lukas Czerner <lczerner>
Date:   Mon Mar 19 23:03:19 2012 -0400

    ext4: rewrite punch hole to use ext4_ext_remove_space()