[OpenWrt-Devel] [PATCH 6/8 v3] ubifs: Use dirty_writeback_interval value for wbuf timer

[Linus Walleij]

On Sun, Feb 17, 2019 at 7:18 PM Sasha Levin <sashal at kernel.org> wrote:
> On Thu, Feb 14, 2019 at 02:24:01PM +0100, Linus Walleij wrote:
> >From: Rafał Miłecki <rafal at milecki.pl>
> >
> >commit 1b7fc2c0069f3864a3dda15430b7aded31c0bfcc upstream.
> >
> >Right now wbuf timer has hardcoded timeouts and there is no place for
> >manual adjustments. Some projects / cases many need that though. Few
> >file systems allow doing that by respecting dirty_writeback_interval
> >that can be set using sysctl (dirty_writeback_centisecs).
> >
> >Lowering dirty_writeback_interval could be some way of dealing with user
> >space apps lacking proper fsyncs. This is definitely *not* a perfect
> >solution but we don't have ideal (user space) world. There were already
> >advanced discussions on this matter, mostly when ext4 was introduced and
> >it wasn't behaving as ext3. Anyway, the final decision was to add some
> >hacks to the ext4, as trying to fix whole user space or adding new API
> >was pointless.
> >
> >We can't (and shouldn't?) just follow ext4. We can't e.g. sync on close
> >as this would cause too many commits and flash wearing. On the other
> >hand we still should allow some trade-off between -o sync and default
> >wbuf timeout. Respecting dirty_writeback_interval should allow some sane
> >cutomizations if used warily.
> >
> >Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
> >Reviewed-by: Boris Brezillon <boris.brezillon at free-electrons.com>
> >Signed-off-by: Richard Weinberger <richard at nod.at>
> >Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
>
> This one looks like a new feature that will also require changes to
> userspace. Is there actual breakage this fixes?

No let's drop it then, the problem I am investigating in OpenWrt and other
distributions (and code dumps) are backported patches: sometimes they
are obviously backported for features, sometimes obviously for fixing something
that was broken, sometimes it is just unclear to me why it has been
backported.

So I guess this was backported for features, so it can be dropped.

Thanks for helping out!
Linus Walleij

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