Re: [PATCH 007 of 9] md: prevent duplicates in bind_rdev_to_array

From: Andrew Morton
Date: Mon Apr 28 2008 - 23:51:32 EST


On Tue, 29 Apr 2008 13:35:27 +1000 NeilBrown <neilb@xxxxxxx> wrote:

>
> From: Dan Williams <dan.j.williams@xxxxxxxxx>
>
> Found when trying to reassemble an active externally managed array.
> Without this check we hit the more noisy "sysfs duplicate" warning in
> the later call to kobject_add.
>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Neil Brown <neilb@xxxxxxx>
>
> ### Diffstat output
> ./drivers/md/md.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff .prev/drivers/md/md.c ./drivers/md/md.c
> --- .prev/drivers/md/md.c 2008-04-29 12:27:57.000000000 +1000
> +++ ./drivers/md/md.c 2008-04-29 12:27:57.000000000 +1000
> @@ -1369,6 +1369,11 @@ static int bind_rdev_to_array(mdk_rdev_t
> MD_BUG();
> return -EINVAL;
> }
> +
> + /* prevent duplicates */
> + if (find_rdev(mddev, rdev->bdev->bd_dev))
> + return -EEXIST;
> +
> /* make sure rdev->size exceeds mddev->size */
> if (rdev->size && (mddev->size == 0 || rdev->size < mddev->size)) {
> if (mddev->pers) {

Smells racy. Do we have enough locking in place here to make this more
than a best-effort thing?
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