linux-kernel - Re: [PATCH V2] ovl: fsync after metadata copy-up via mount option "fsync=strict"

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Message-ID: <CAOQ4uxjkVcY7z8JCshmsCfn1=JUcxDG8vyJQ+ssdeBmGrZ=eKg@mail.gmail.com>
Date: Fri, 30 Aug 2024 11:26:42 +0200
From: Amir Goldstein <amir73il@...il.com>
To: Miklos Szeredi <miklos@...redi.hu>, Fei Lv <feilv@...micro.com>
Cc: linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	lianghuxu@...micro.com
Subject: Re: [PATCH V2] ovl: fsync after metadata copy-up via mount option "fsync=strict"

On Thu, Aug 29, 2024 at 6:23 PM Amir Goldstein <amir73il@...il.com> wrote:
>
> On Thu, Aug 29, 2024 at 2:51 PM Miklos Szeredi <miklos@...redi.hu> wrote:
> >
> > On Thu, 29 Aug 2024 at 12:29, Amir Goldstein <amir73il@...il.com> wrote:
> >
> > > But maybe we can ignore crash safety of metacopy on ubifs, because
> > > 1. the ubifs users may not be using this feature
> > > 2. ubifs may be nice and takes care of ordering O_TMPFILE
> > >     metadata updates before exposing the link
> > >
> > > Then we can do the following:
> > > IF (metacopy_enabled)
> > >     fsync only in ovl_copy_up_file()
> > > ELSE
> > >     fsync only in ovl_copy_up_metadata()
> > >
> > > Let me know what you think.
> >
> > Sounds like a good compromise.
> >
>
> Fei,
>
> Could you please test the attached patch and confirm that your
> use case does not depend on metacopy enabled?
>
> In any case, I am holding on to your patch in case someone reports
> a performance regression with this unconditional fsync approach.
>

Well, it's a good thing that I took Miklois' advice to make the fsync
option implicit, because the original patch had 2 bugs detected by fstest:
1. missing O_LARGEFILE
2. trying to fsync special files

Please see uptodate patch at:
https://github.com/amir73il/linux/commits/ovl-fsync/

If there are no complaints, I will queue this up for v6.12.
Fei, please provide your Tested-by.

Thanks,
Amir.