On Tue, Jan 31, 2023 at 5:07 PM Xiao Ni <xni@xxxxxxxxxx> wrote:
>
> It has added io_acct_set for raid0/raid5 io accounting and it needs to
> alloc md_io_acct in the i/o path. They are free when the bios come back
> from member disks. Now we don't have a method to monitor if those bios
> are all come back. In the takeover process, it needs to free the raid0
> memory resource including the memory pool for md_io_acct. But maybe some
> bios are still not returned. When those bios are returned, it can cause
> panic bcause of introducing NULL pointer or invalid address.
Could you please provide more information about the panic?
Thanks,
Song
>
> This patch adds io_acct_cnt. So when stopping raid0, it can use this
> to wait until all bios come back. And I did a simple performance test
> with fio:
>
> -direct=1 -ioengine=libaio -iodepth=128 -bs=64K -rw=write -numjobs=1
> With the patch set: 2676MB/s, without the patch set: 2670MB/s
> -direct=1 -ioengine=libaio -iodepth=128 -bs=64K -rw=read -numjobs=1
> With the patch set: 4676MB/s, without the patch set: 4654MB/s
>
> Reported-by: Fine Fan <ffan@xxxxxxxxxx>
> Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> Signed-off-by: Xiao Ni <xni@xxxxxxxxxx>
> ---
> v2: Fixes a bug. It needs to check if io_acct is dead state when
> resurrecting
> drivers/md/md.c | 23 ++++++++++++++++++++++-
> drivers/md/md.h | 9 ++++++---
> drivers/md/raid0.c | 6 ++++++
> 3 files changed, 34 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 0eb31bef1f01..66c3639bdbfd 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -683,6 +683,7 @@ void mddev_init(struct mddev *mddev)
> atomic_set(&mddev->flush_pending, 0);
> init_waitqueue_head(&mddev->sb_wait);
> init_waitqueue_head(&mddev->recovery_wait);
> + init_waitqueue_head(&mddev->wait_io_acct);
> mddev->reshape_position = MaxSector;
> mddev->reshape_backwards = 0;
> mddev->last_sync_action = "none";
> @@ -8604,13 +8605,28 @@ void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
> }
> EXPORT_SYMBOL_GPL(md_submit_discard_bio);
>
> +static void io_acct_release(struct percpu_ref *ref)
> +{
> + struct mddev *mddev = container_of(ref, struct mddev, io_acct_cnt);
> +
> + wake_up(&mddev->wait_io_acct);
> +}
> +
> int acct_bioset_init(struct mddev *mddev)
> {
> int err = 0;
>
> - if (!bioset_initialized(&mddev->io_acct_set))
> + if (!bioset_initialized(&mddev->io_acct_set)) {
> + err = percpu_ref_init(&mddev->io_acct_cnt, io_acct_release,
> + PERCPU_REF_ALLOW_REINIT, GFP_KERNEL);
> + if (err)
> + return err;
> +
> err = bioset_init(&mddev->io_acct_set, BIO_POOL_SIZE,
> offsetof(struct md_io_acct, bio_clone), 0);
> + if (err)
> + percpu_ref_exit(&mddev->io_acct_cnt);
> + }
> return err;
> }
> EXPORT_SYMBOL_GPL(acct_bioset_init);
> @@ -8618,6 +8634,7 @@ EXPORT_SYMBOL_GPL(acct_bioset_init);
> void acct_bioset_exit(struct mddev *mddev)
> {
> bioset_exit(&mddev->io_acct_set);
> + percpu_ref_exit(&mddev->io_acct_cnt);
> }
> EXPORT_SYMBOL_GPL(acct_bioset_exit);
>
> @@ -8625,9 +8642,11 @@ static void md_end_io_acct(struct bio *bio)
> {
> struct md_io_acct *md_io_acct = bio->bi_private;
> struct bio *orig_bio = md_io_acct->orig_bio;
> + struct mddev *mddev = md_io_acct->mddev;
>
> orig_bio->bi_status = bio->bi_status;
>
> + percpu_ref_put(&mddev->io_acct_cnt);
> bio_end_io_acct(orig_bio, md_io_acct->start_time);
> bio_put(bio);
> bio_endio(orig_bio);
> @@ -8650,6 +8669,8 @@ void md_account_bio(struct mddev *mddev, struct bio **bio)
> md_io_acct = container_of(clone, struct md_io_acct, bio_clone);
> md_io_acct->orig_bio = *bio;
> md_io_acct->start_time = bio_start_io_acct(*bio);
> + md_io_acct->mddev = mddev;
> + percpu_ref_get(&mddev->io_acct_cnt);
>
> clone->bi_end_io = md_end_io_acct;
> clone->bi_private = md_io_acct;
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 6335cb86e52e..c0e869bdde42 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -513,6 +513,8 @@ struct mddev {
> * metadata and bitmap writes
> */
> struct bio_set io_acct_set; /* for raid0 and raid5 io accounting */
> + struct percpu_ref io_acct_cnt;
> + wait_queue_head_t wait_io_acct;
>
> /* Generic flush handling.
> * The last to finish preflush schedules a worker to submit
> @@ -710,9 +712,10 @@ struct md_thread {
> };
>
> struct md_io_acct {
> - struct bio *orig_bio;
> - unsigned long start_time;
> - struct bio bio_clone;
> + struct mddev *mddev;
> + struct bio *orig_bio;
> + unsigned long start_time;
> + struct bio bio_clone;
> };
>
> #define THREAD_WAKEUP 0
> diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
> index b536befd8898..f732ca8e2e1f 100644
> --- a/drivers/md/raid0.c
> +++ b/drivers/md/raid0.c
> @@ -753,6 +753,12 @@ static void *raid0_takeover(struct mddev *mddev)
>
> static void raid0_quiesce(struct mddev *mddev, int quiesce)
> {
> + if (quiesce) {
> + percpu_ref_kill(&mddev->io_acct_cnt);
> + wait_event(mddev->wait_io_acct,
> + percpu_ref_is_zero(&mddev->io_acct_cnt));
> + } else if (percpu_ref_is_dying(&mddev->io_acct_cnt))
> + percpu_ref_resurrect(&mddev->io_acct_cnt);
> }
>
> static struct md_personality raid0_personality=
> --
> 2.32.0 (Apple Git-132)
>
