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Date:      Wed, 28 Nov 2018 17:42:05 -0700
From:      JD <jd1008@gmail.com>
To:        Markus Hoenicka <markus.hoenicka@mhoenicka.de>,  freebsd-questions@freebsd.org
Subject:   Re: ROX-Filer: overwriting a file on an USB drive truncates it
Message-ID:  <5BFF35DD.8050808@gmail.com>
In-Reply-To: <4ee20fc51b13465edcec6d8456be7cf0@mhoenicka.de>
References:  <4ee20fc51b13465edcec6d8456be7cf0@mhoenicka.de>

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On 11/28/2018 05:23 PM, Markus Hoenicka wrote:
> Hi,
>
> I've recently upgraded my laptop to:
>
> FreeBSD wombat 11.2-RELEASE-p4 FreeBSD 11.2-RELEASE-p4 #0: Thu Sep 27 
> 08:16:24 UTC 2018 
> root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64
>
> I've also updated all installed packages.
>
> I keep running into a nasty file copying bug that does not seem to 
> have occurred previously. Result is that overwriting an existing file 
> on an USB drive causes this file to be truncated instead of being 
> overwritten, which means data loss.
>
> How to reproduce:
>
> After logging in, I start an Xfce session manually:
>
> startxfce4 --with-ck-launch
>
> mount stick in an xterm, as per handbook. Note that I've set up user 
> mounting of USB drives:
>
> mount -t msdosfs -o -m=644,-M=755 /dev/da0s1 /stick/markus
>
> open source directory (on hard drive) in a ROX-Filer window
> open target directory (on usb drive) in another ROX-Filer window
>
> drag&drop a file from source over an existing copy on target
>
> dialog box asks if it is ok to overwrite which I acknowledge
>
> ROX-Filer window shows the correct file size immediately after 
> copying, and after rescanning the directory. ls -al 
> /stick/markus/targetdir also shows the correct file size at this point.
>
> umount /stick/markus fails because the device is busy. fstat shows 
> that the ROX-Filer process keeps it busy
>
> now I can either use umount -f /stick/markus to forcibly unmount the 
> stick, or I log out of the X session and then use umount /stick/markus 
> without problems
>
> then mount the stick again as above, or try on a different computer
>
> ls -al /stick/markus/targetdir shows a target file size of zero.
>
> It appears that the new data are never flushed to the disk. I've even 
> tried to run umount /stick/markus before umount -f /stick/markus, as 
> this should perform a flush according to the umount man page. This bug 
> appears to be specific to ROX-Filer. I could not reproduce this using 
> Thunar, or plain ol' cp. This bug also appears to be specific to USB 
> target drives, as I cannot reproduce this when overwriting files on 
> the hard drive. I do not think the problem is related to a faulty file 
> system on the target drive as I can reproduce this with just about any 
> thumbdrive and external disk lying around.
>
> I've been using ROX-Filer for ages, but I've noticed that neither 
> mailing lists nor bug tracker seem to be active. Is it about time to 
> move on?
>
> thanks
> Markus
>
Hi Markus,
the short of the long ....
I have seen this problem man many times.
I had found out that the usb stick was a 1X speed stick,
and it took the FS and io drivers below it a long time to
allocate the free blocks needed to write out the new data.

The new blocks are allocated from the list of
"oldest blocks on the free list".
That is how a flash fs blocks are handled.
The old blocks are released to the free list.
Thus a 1X flash stick would take forever to do this and
receive all the data that is in the dirty memory blocks.

I am not saying that YOUR flash device is 1X device.
Merely stating that perhaps you are being impatient????





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