Bug 191391

Summary:	Cannot write Arch image to usb stick using dd with kernel 4.10
Product:	IO/Storage	Reporter:	darkbasic (darkbasic)
Component:	Block Layer	Assignee:	Jens Axboe (axboe)
Status:	RESOLVED OBSOLETE
Severity:	normal
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	4.10rc1.r15.g8f18e4d03ed8	Subsystem:
Regression:	No	Bisected commit-id:

Description darkbasic 2016-12-28 18:07:13 UTC

I wanted to test kernel 4.10 because of the automatic throttling of writeback queues on the block side. In fact with 4.8.13 every time I copy big files to my usb stick the system becomes unresponsive.
Unfortunately with 4.10 when I try to write the Arch image to an usb stick using "sudo dd if=archlinux-2016.12.01-dual.iso of=/dev/sdb bs=1 status=progress" it instantly finishes (like when you write to the cache but you still have to sync). It wrote something to the stick, but the image doesn't boot. Manually syncing does not help. Everything works flawlessly with kernel 4.8.

Comment 1 Jens Axboe 2016-12-28 18:14:40 UTC

How big is the image and how much RAM does the machine have? And did you really use bs=1, or did you use bs=1M?

Comment 2 darkbasic 2016-12-28 19:12:43 UTC

A typo, I used bs=1M. The image is 799M and the laptop has 8GB of ram.

Comment 3 darkbasic 2016-12-30 00:45:32 UTC

Did you manage to reproduce it? If not, is there any way I can help you to debug it?

Comment 4 Jens Axboe 2016-12-30 16:20:12 UTC

I haven't checked yet, out of office until Tuesday next week. But it sounds very odd.

Comment 5 darkbasic 2016-12-31 01:20:32 UTC

I'm not sure at all that the regression is caused by the automatic throttling of writeback queues, but it surely happens with kernel 4.10.

Comment 6 darkbasic 2017-02-06 17:04:59 UTC

Later versions of 4.10 didn't have this problem, so I'm closing.