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