On Sun, Feb 17, 2019 at 7:18 PM Sasha Levin <sashal@xxxxxxxxxx> wrote: > On Thu, Feb 14, 2019 at 02:24:01PM +0100, Linus Walleij wrote: > >From: Rafał Miłecki <rafal@xxxxxxxxxx> > > > >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@xxxxxxxxxx> > >Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> > >Signed-off-by: Richard Weinberger <richard@xxxxxx> > >Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> > > 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
