[EXT] Re: UBIFS file has zeroes at the end after an unclean reboot

[beanhuo@xxxxxxxxxx (Bean Huo (beanhuo))]

Hi,Richard
Thanks.  
it is Async mode ubifs  mounted. After random powerloss testing, found that there is one file contains huge zeroes data.
But UBIFS didn't crash and no ECC/CRC error.

As for the below patch, doesn?t exist, we will try that.
Thanks again.

>Am Montag, 23. Juli 2018, 13:12:09 CEST schrieb Bean Huo (beanhuo):
>> Hi, Richard
>> Do you have good suggestions about how to prevent this condiciton:
>http://www.linux-mtd.infradead.org/faq/ubifs.html#L_end_hole ?
>
>Well, I'd start with making sure that userspaces does the right thing(tm) and
>to be very sure what kind of problem the user is facing.
>Did you verify whether the affected program is using fsync/fdatasync?
>
>Does your kernel include
>commit 1b7fc2c0069f3864a3dda15430b7aded31c0bfcc
>Author: Rafa? Mi?ecki <rafal at milecki.pl>
>Date:   Tue Sep 20 10:36:15 2016 +0200
>
>    ubifs: Use dirty_writeback_interval value for wbuf timer
>
>    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: Rafa? Mi?ecki <rafal at milecki.pl>
>    Reviewed-by: Boris Brezillon <boris.brezillon at free-electrons.com>
>    Signed-off-by: Richard Weinberger <richard at nod.at> ?
>
>Thanks,
>//richard