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

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Message-ID: <CAOQ4uxgKC1SgjMWre=fUb00v8rxtd6sQi-S+dxR8oDzAuiGu8g@mail.gmail.com>
Date: Fri, 30 Aug 2024 14:23:16 +0200
From: Amir Goldstein <amir73il@...il.com>
To: Lv Fei（吕飞） <feilv@...micro.com>
Cc: Miklos Szeredi <miklos@...redi.hu>, 
	"linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	Xu Lianghu（徐良虎） <lianghuxu@...micro.com>
Subject: Re: [PATCH V2] ovl: fsync after metadata copy-up via mount option "fsync=strict"

On Fri, Aug 30, 2024 at 1:52 PM Lv Fei（吕飞） <feilv@...micro.com> wrote:
>
> > 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.
>
> We do not enable metacopy.
> Tested this patch and it also solved our issue.

Hi Fei,

Thanks for approving.
I added Reported-and-tested-by and pushed to overlayfs-next.

Now we just need to hope that users won't come shouting about
performance regressions.

Thanks,
Amir.