On Mon, 07 Feb 2011 14:21:48 -0500 Chris Mason <chris.mason@xxxxxxxxxx> wrote:
> md_make_request was calling bio_sectors() for part_stat_add
> after it was calling the make_request function. This is
> bad because the make_request function can free the bio and
> because the bi_size field can change around.
>
> The fix here was suggested by Jens Axboe. It saves the
> sector count before the make_request call. I hit this
> with CONFIG_DEBUG_PAGEALLOC turned on while trying to break
> his pretty fusionio card.
Thanks Chris!!
I've added it to my queue of md fixes (which I really must send of soon) and
tagged it for -stable.
NeilBrown
>
> Signed-off-by: Chris Mason <chris.mason@xxxxxxxxxx>
> ---
> drivers/md/md.c | 9 +++++++--
> 1 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index b76cfc8..a7d3c3c 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -287,6 +287,7 @@ static int md_make_request(struct request_queue *q, struct bio *bio)
> mddev_t *mddev = q->queuedata;
> int rv;
> int cpu;
> + unsigned int sectors;
>
> if (mddev == NULL || mddev->pers == NULL
> || !mddev->ready) {
> @@ -311,12 +312,16 @@ static int md_make_request(struct request_queue *q, struct bio *bio)
> atomic_inc(&mddev->active_io);
> rcu_read_unlock();
>
> + /*
> + * save the sectors now since our bio can
> + * go away inside make_request
> + */
> + sectors = bio_sectors(bio);
> rv = mddev->pers->make_request(mddev, bio);
>
> cpu = part_stat_lock();
> part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
> - part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
> - bio_sectors(bio));
> + part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw], sectors);
> part_stat_unlock();
>
> if (atomic_dec_and_test(&mddev->active_io) && mddev->suspended)
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