Re: [PATCH 1/3] raid0, linear, md: add error_handlers for raid0 and linear

On Thu, Dec 16, 2021 at 10:53 PM Mariusz Tkaczyk
[off-list ref] wrote:

Patch 62f7b1989c0 ("md raid0/linear: Mark array as 'broken' and fail BIOs
if a member is gone") allowed to finish writes earlier (before level
dependent actions) for non-redundant arrays.

To achieve that MD_BROKEN is added to mddev->flags if drive disappearance
is detected. This is done in is_mddev_broken() which is confusing and not
consistent with other levels where error_handler() is used.
This patch adds appropriate error_handler for raid0 and linear.

It also adopts md_error(), we only want to call .error_handler for those
levels. mddev->pers->sync_request is additionally checked, its existence
implies a level with redundancy.

Usage of error_handler causes that disk failure can be requested from
userspace. User can fail the array via #mdadm --set-faulty command. This
is not safe and will be fixed in mdadm. It is correctable because failed
state is not recorded in the metadata. After next assembly array will be
read-write again. For safety reason is better to keep MD_BROKEN in
runtime only.

Hi Mariusz

Let me call them chapter[1-4]

Could you explain more about 'mdadm --set-faulty' part? I've read this
patch. But I don't
know the relationship between the patch and chapter4.

In patch2, you write "As in previous commit, it causes that #mdadm
--set-faulty is able to
mark array as failed." I tried to run command `mdadm /dev/md0 -f
/dev/sda`. md0 is a raid0.
It can't remove sda from md0.

Best Regards
Xiao