Re: [PATCH 1/2] common: provide generic block error injection helper

[Anand Jain <anand.jain@oracle.com>]

On 04/07/2022 17:03, Christoph Hellwig wrote:
> Various tests have more or less copy and pasted code to enable and
> disable block layer "fail make request" error injection.  Move that
> to a set of common helpers and use those in the drivers.
> 

> btrfs/150 differened from the other two in a few ways, like selecting
> a not quite as big number to fail all requests in the small critical
> section and clearing a bunch of never set attributes in the failure
> injection configuration, but none of those matter for the test
> execution.

Hm. more below.


> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   common/inject     | 33 +++++++++++++++++++++++++++++++++
>   tests/btrfs/088   | 24 +++++-------------------
>   tests/btrfs/150   | 27 +++++----------------------
>   tests/generic/019 | 44 +++++++++-----------------------------------
>   4 files changed, 52 insertions(+), 76 deletions(-)
> 
> diff --git a/common/inject b/common/inject
> index 6b590804..137ff5fd 100644
> --- a/common/inject
> +++ b/common/inject
> @@ -111,3 +111,36 @@ _scratch_inject_error()
>   		_fail "Cannot inject error ${type} value ${value}."
>   	fi
>   }
> +
> +# enable block error injection globally
> +_enable_fail_make_request()
> +{
> +	echo 100 > $DEBUGFS_MNT/fail_make_request/probability

> +	echo 9999999 > $DEBUGFS_MNT/fail_make_request/times

Instead, can we do
    printf %#x -1  > $DEBUGFS_MNT/fail_make_request/times
(as in the documentation).


<snip>

> @@ -25,24 +26,6 @@ _require_fail_make_request
>   _require_scratch_dev_pool 2
>   _scratch_dev_pool_get 2
>   
> -SYSFS_BDEV=`_sysfs_dev $SCRATCH_DEV`
> -enable_io_failure()
> -{
> -	echo 100 > $DEBUGFS_MNT/fail_make_request/probability
> -	echo 1000 > $DEBUGFS_MNT/fail_make_request/times
> -	echo 0 > $DEBUGFS_MNT/fail_make_request/verbose


> -	echo 1 > $DEBUGFS_MNT/fail_make_request/task-filter
Only extra line in btrfs/150 is the above line (or did I miss any)?
Which is deleted in this patch.

Per 'task-filter' documentation
--------------
- /sys/kernel/debug/fail*/task-filter:

         Format: { 'Y' | 'N' }

         A value of 'N' disables filtering by process (default).
         Any positive value limits failures to only processes indicated by
         /proc/<pid>/make-it-fail==1.
--------------

<snip>

> -	enable_io_failure
> -
> +	_enable_fail_make_request
> +	_start_fail_dev $SCRATCH_DEV
>   	result=$(bash -c "
>   	if [ \$((\$\$ % 2)) == 1 ]; then

>   		echo 1 > /proc/\$\$/make-it-fail

  So this won't work now.

Thanks, Anand