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

[Sasha Levin <sashal@kernel.org>]

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?

--
Thanks,
Sasha