Bug 1700295

Summary:	The data couldn't be flushed immediately even with O_SYNC in glfs_create or with glfs_fsync/glfs_fdatasync after glfs_write.
Product:	[Community] GlusterFS	Reporter:	Xiubo Li <xiubli>
Component:	core	Assignee:	Xiubo Li <xiubli>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	urgent	Docs Contact:
Priority:	high
Version:	6	CC:	amarts, amukherj, bugs, pasik, pkarampu, prasanna.kalever
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Last Closed:	2020-03-17 04:09:19 UTC	Type:	Bug
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Description Xiubo Li 2019-04-16 09:26:32 UTC

Description of problem:

In gluster-block project we had hit a case where we will sometimes get old block metadata with blockGetMetaInfo(), which will glfs_read from the block file, after updating the block metadata with GB_METAUPDATE_OR_GOTO(), which will glfs_write the block file.

In GB_METAUPDATE_OR_GOTO, it basically open the metafile with the O_SYNC, write the new details and close it in-place, which should flush the data to metafile. But looks like in glusterfs-api-devel-6.0-0.4.rc1.fc29.x86_64 it will not be flushed in time.

Version-Release number of selected component (if applicable):




How reproducible:
In RHEL 7 by using the gluster-blocl/tests/basic.t script with glusterfs-api-devel-6.0-0.4.rc1.fc29.x86_64 it is very easy to reproduce, in my setups almost 40%.

Steps to Reproduce:
1. git clone https://github.com/gluster/gluster-block.git
2. build it from source and install it
3. install the tcmu-runner package or use the upstream code
4. $ ./tests/basic.t



Actual results:
Delete will fail sometimes

Expected results:
Delete should be success

Additional info:

More detail please see
https://github.com/gluster/gluster-block/issues/204
https://github.com/gluster/gluster-block/pull/209