On Thursday May 8, dan.j.williams@xxxxxxxxx wrote:
> On Thu, 2008-05-08 at 11:46 -0700, Dan Williams wrote:
> Subject: md: tell blk-core about device_lock for protecting the queue flags
> From: Dan Williams <dan.j.williams@xxxxxxxxx>
>
> Now that queue flags are no longer atomic (commit:
> 75ad23bc0fcb4f992a5d06982bf0857ab1738e9e) blk-core checks the queue is locked
> via ->queue_lock. As noticed by Neil conf->device_lock already satisfies this
> requirement.
>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
>
> drivers/md/linear.c | 6 ++++++
> drivers/md/multipath.c | 6 ++++++
> drivers/md/raid0.c | 6 ++++++
> drivers/md/raid1.c | 7 ++++++-
> drivers/md/raid10.c | 7 ++++++-
> drivers/md/raid5.c | 2 ++
> include/linux/raid/linear.h | 3 ++-
> include/linux/raid/raid0.h | 1 +
> 8 files changed, 35 insertions(+), 3 deletions(-)
>
>
> diff --git a/drivers/md/linear.c b/drivers/md/linear.c
> index 0b85117..d026f08 100644
> --- a/drivers/md/linear.c
> +++ b/drivers/md/linear.c
> @@ -122,6 +122,10 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
> cnt = 0;
> conf->array_size = 0;
>
> + spin_lock_init(&conf->device_lock);
> + /* blk-core uses queue_lock to verify protection of the queue flags */
> + mddev->queue->queue_lock = &conf->device_lock;
> +
> rdev_for_each(rdev, tmp, mddev) {
> int j = rdev->raid_disk;
> dev_info_t *disk = conf->disks + j;
> @@ -133,8 +137,10 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
>
> disk->rdev = rdev;
>
> + spin_lock(&conf->device_lock);
> blk_queue_stack_limits(mddev->queue,
> rdev->bdev->bd_disk->queue);
> + spin_unlock(&conf->device_lock);
> /* as we don't honour merge_bvec_fn, we must never risk
> * violating it, so limit ->max_sector to one PAGE, as
> * a one page request is never in violation.
This shouldn't be necessary.
There is no actual race here -- mddev->queue->queue_flags is not going to be
accessed by anyone else until do_md_run does
mddev->queue->make_request_fn = mddev->pers->make_request;
which is much later.
So we only need to be sure that "queue_is_locked" doesn't complain.
And as q->queue_lock is still NULL at this point, it won't complain.
I think that the *only* change that is needs is to put
> + /* blk-core uses queue_lock to verify protection of the queue flags */
> + mddev->queue->queue_lock = &conf->device_lock;
after each
> + spin_lock_init(&conf->device_lock);
i.e. in raid1.c, raid10.c and raid5.c
??
NeilBrown
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