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Date:   Fri, 6 Mar 2020 09:15:23 -0500
From:   "Theodore Y. Ts'o" <tytso@mit.edu>
To:     Alok Jain <jain.alok103@gmail.com>
Cc:     linux-ext4@vger.kernel.org, Andreas Dilger <adilger@dilger.ca>
Subject: Re: Ext4 errors in linux /var/log/messages
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On Fri, Mar 06, 2020 at 07:29:22PM +0530, Alok Jain wrote:
> Hi Guys,
> 
> Thanks for providing the forum to check the issue, I already got
> really helpful responses and need one more help wrt to EXT4 log
> messages coming in /var/log/messages file
> 
> 1) I have iSCSI device attached to my VM
> 2) Copied and extracted files in the attached device
> 3) Unmount and disconnected the device, post disconnect operation I
> can see lots of EXT4 file system errors in /var/log/messages file,
> attaching the same (err.txt) for review.
> 
> I am not sure what these log messages are correspond to as the device
> was already disconnected at  Feb I1:22:42, but th*e ext4 log messages
> came after that, can you please review and share your findings.

There's nothing really deep here.  Ext4 wasn't able to write to
/dev/sdd1.  Assuming that /dev/sdd is your iSCSI device, it's probably
because the connection to the iSCSI device had gotten disrupted.  This
is similar to what you might see if you were writing to a USB
thumbstick and the USB device is unceremoniously yanked out.

One possible scenario is thar while the umount was *started*, but it
had not completed writing out dirty blocks before the iSCSI device was
disconnected.  If that's true, this would be a case of operator error.

	       	  	       	    	  - Ted