[dm-devel] [PATCH v3 1/2] md raid0/linear: Mark array as 'broken' and fail BIOs if a member is gone

[Song Liu]

> On Aug 22, 2019, at 9:13 AM, Guilherme G. Piccoli <gpiccoli at canonical.com> wrote:
> 
> Currently md raid0/linear are not provided with any mechanism to validate
> if an array member got removed or failed. The driver keeps sending BIOs
> regardless of the state of array members, and kernel shows state 'clean'
> in the 'array_state' sysfs attribute. This leads to the following
> situation: if a raid0/linear array member is removed and the array is
> mounted, some user writing to this array won't realize that errors are
> happening unless they check dmesg or perform one fsync per written file.
> Despite udev signaling the member device is gone, 'mdadm' cannot issue the
> STOP_ARRAY ioctl successfully, given the array is mounted.

[...]

> drivers/md/md-linear.c |  9 +++++++++
> drivers/md/md.c        | 22 ++++++++++++++++++----
> drivers/md/md.h        |  3 +++
> drivers/md/raid0.c     | 10 ++++++++++
> 4 files changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
> index 7354466ddc90..0479ccdbdeeb 100644
> --- a/drivers/md/md-linear.c
> +++ b/drivers/md/md-linear.c
> @@ -258,6 +258,15 @@ static bool linear_make_request(struct mddev *mddev, struct bio *bio)
> 		     bio_sector < start_sector))
> 		goto out_of_bounds;
> 
> +	if (unlikely(!(tmp_dev->rdev->bdev->bd_disk->flags & GENHD_FL_UP))) {
> +		if (!test_bit(MD_BROKEN, &mddev->flags))
> +			pr_warn("md: %s: linear array has a missing/failed member\n",
> +				mdname(mddev));
> +		set_bit(MD_BROKEN, &mddev->flags);
> +		bio_io_error(bio);
> +		return true;
> +	}
> +

Maybe we can somehow put this block in a helper and use it in both raid0
and linear code?

Otherwise, looks good to me. 

Thanks,
Song