Re: [PATCH 6/8 v3] ubifs: Use dirty_writeback_interval value for wbuf timer

[Richard Weinberger <richard@nod.at>]

Am Sonntag, 17. Februar 2019, 19:18:02 CET schrieb Sasha Levin:
> On Thu, Feb 14, 2019 at 02:24:01PM +0100, Linus Walleij wrote:
> >From: Rafał Miłecki <rafal@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@milecki.pl>
> >Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> >Signed-off-by: Richard Weinberger <richard@nod.at>
> >Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> 
> This one looks like a new feature that will also require changes to
> userspace. Is there actual breakage this fixes?

IIRC that's why I never tagged it for -stable.
Maybe there is some other odds it fixes and I'm not aware of. Linus?

Thanks,
//richard