Bug 1535401

Summary:	ioprocess writefile with direct=True does not perform direct I/O
Product:	[oVirt] ovirt-distribution	Reporter:	Nir Soffer <nsoffer>
Component:	ioprocess	Assignee:	Nir Soffer <nsoffer>
ioprocess sub component:	General	QA Contact:	Avihai <aefrat>
Status:	CLOSED WONTFIX	Docs Contact:
Severity:	high
Priority:	high	CC:	ebenahar, lsvaty, tnisan, ylavi
Version:	4.2.1
Target Milestone:	---
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2018-06-10 15:26:51 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	Storage	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1535370

Description Nir Soffer 2018-01-17 10:11:32 UTC

Description of problem:

IOProcessClient.writefile() has a direct flag, set to False by default. When set
to True, the caller expects that ioprocess would use direct I/O (O_DIRECT), and
ioprocess has code to handle this flag, but it code is misplaced so the file is
opened without O_DIRECT, and the call is not doing buffered I/O.

We know about one user of this code - vdsm - and it does not use the direct flag,
but we want to change it to use this flag (see bug 1535370).

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

How reproducible:
Always

Steps to Reproduce:
1. Run ioprocess using strace -f
2. Call IProcessClient.writefile() with direct=True

Actual results:
In strace output we see that file was not opened with O_DIRECT

Expected results:
open file with O_DIRECT when direct is True.

Note: version is wrong, bugzilla does not provide all ioprocess versions.

Comment 1 Nir Soffer 2018-01-21 14:44:43 UTC

Tal, this bug blocks urgent vdsm bug targeted to 4.2.1. Suggesting 4.2.1.

I think both bugs can be deffered to 4.2.2 or later, since using direct I/O for
writing tiny files is not important.

Comment 2 Yaniv Kaul 2018-06-07 09:49:50 UTC

(In reply to Nir Soffer from comment #1)
> Tal, this bug blocks urgent vdsm bug targeted to 4.2.1. Suggesting 4.2.1.
> 
> I think both bugs can be deffered to 4.2.2 or later, since using direct I/O
> for
> writing tiny files is not important.

I think it may miss 4.2.4 as well. Shall we target it to 4.2.5?

Comment 3 Tal Nisan 2018-06-07 15:12:03 UTC

(In reply to Yaniv Kaul from comment #2)
> (In reply to Nir Soffer from comment #1)
> > Tal, this bug blocks urgent vdsm bug targeted to 4.2.1. Suggesting 4.2.1.
> > 
> > I think both bugs can be deffered to 4.2.2 or later, since using direct I/O
> > for
> > writing tiny files is not important.
> 
> I think it may miss 4.2.4 as well. Shall we target it to 4.2.5?

Yes, the patches don't seem like they are going to converge by then

Comment 4 Nir Soffer 2018-06-10 15:26:51 UTC

I'm closing this as there is no need to use direct I/O for writing small files,
and ioprocess should not be used to write files. There is no point in wasting 
time to improve ioprocess to do stuff it should not do.