Hi!
The corrupt_bio_byte feature of dm-flakey has been broken for a long
time. In corrupt_bio_data(), bio_cur_bytes(bio) and bio_data(bio) always
return 0 and NULL, so no data corruption is done. I believe this was
caused by the integration of blk-mq in Linux 4.0. Through git bisecting
I found that for underlying loop devices, this commit broke
corrupt_bio_byte:
commit b5dd2f6047ca108001328aac0e8588edd15f1778
Author: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Date: Wed Dec 31 13:22:57 2014 +0000
block: loop: improve performance via blk-mq
For underlying scsi devices it was broken some time before that. If
this conclusion is correct, does anyone have the time to fix dm-flakey
by converting it to use blk-mq? I don't think I have the expertise to do
it myself.
To test this feature I used the following commands to set up a flakey
device that corrupts the first byte of the underlying device on reads:
dd if=/dev/urandom of=disk bs=1M count=100
losetup -f disk
dmsetup create -r stuff <<< '0 204800 flakey /dev/loop0 0 1 100
5 corrupt_bio_byte 1 r 0 0'
dd if=disk count=1 status=none | hexdump
dd if=/dev/dm-0 count=1 status=none | hexdump
Expected result is that the output from the two dd invocations differ in
the first byte.
Thanks!
--
Anton Eliasson
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
