| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <c085664e-3a52-4a1c-b973-8d2ba6e5d509@redhat.com>
Date: Wed, 16 Apr 2025 14:20:35 +0800
From: Xiao Ni <xni@...hat.com>
To: Yu Kuai <yukuai1@...weicloud.com>, axboe@...nel.dk, song@...nel.org,
yukuai3@...wei.com
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-raid@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH 3/4] md: fix is_mddev_idle()
在 2025/4/12 下午3:32, Yu Kuai 写道:
> From: Yu Kuai <yukuai3@...wei.com>
>
> If sync_speed is above speed_min, then is_mddev_idle() will be called
> for each sync IO to check if the array is idle, and inflihgt sync_io
> will be limited if the array is not idle.
>
> However, while mkfs.ext4 for a large raid5 array while recovery is in
> progress, it's found that sync_speed is already above speed_min while
> lots of stripes are used for sync IO, causing long delay for mkfs.ext4.
>
> Root cause is the following checking from is_mddev_idle():
>
> t1: submit sync IO: events1 = completed IO - issued sync IO
> t2: submit next sync IO: events2 = completed IO - issued sync IO
> if (events2 - events1 > 64)
>
> For consequence, the more sync IO issued, the less likely checking will
> pass. And when completed normal IO is more than issued sync IO, the
> condition will finally pass and is_mddev_idle() will return false,
> however, last_events will be updated hence is_mddev_idle() can only
> return false once in a while.
>
> Fix this problem by changing the checking as following:
>
> 1) mddev doesn't have normal IO completed;
> 2) mddev doesn't have normal IO inflight;
> 3) if any member disks is partition, and all other partitions doesn't
> have IO completed.
>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
> drivers/md/md.c | 78 ++++++++++++++++++++++++++-----------------------
> drivers/md/md.h | 3 +-
> 2 files changed, 43 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 8966c4afc62a..19da93f8912c 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -8619,50 +8619,54 @@ void md_cluster_stop(struct mddev *mddev)
> put_cluster_ops(mddev);
> }
>
> -static int is_mddev_idle(struct mddev *mddev, int init)
> +static bool is_rdev_idle(struct md_rdev *rdev, bool init)
> +{
> + unsigned long last_events = rdev->last_events;
> +
> + if (!bdev_is_partition(rdev->bdev))
> + return true;
For md array, I think is_rdev_idle is not useful. Because
mddev->last_events must be increased while upper ios come in and idle
will be set to false. For dm array, mddev->last_events can't work. So
is_rdev_idle is for dm array. If member disk is one partition,
is_rdev_idle alwasy returns true, and is_mddev_idle always return true.
It's a bug here. Do we need to check bdev_is_partition here?
Best Regards
Xiao
> +
> + rdev->last_events = part_stat_read_accum(rdev->bdev->bd_disk->part0,
> + sectors) -
> + part_stat_read_accum(rdev->bdev, sectors);
> +
> + if (!init && rdev->last_events > last_events)
> +
> + return true;
> +}
> +
> +/*
> + * mddev is idle if following conditions are match since last check:
> + * 1) mddev doesn't have normal IO completed;
> + * 2) mddev doesn't have inflight normal IO;
> + * 3) if any member disk is partition, and other partitions doesn't have IO
> + * completed;
> + *
> + * Noted this checking rely on IO accounting is enabled.
> + */
> +static bool is_mddev_idle(struct mddev *mddev, int init)
> {
> struct md_rdev *rdev;
> - int idle;
> - int curr_events;
> + bool idle = true;
>
> - idle = 1;
> - rcu_read_lock();
> - rdev_for_each_rcu(rdev, mddev) {
> - struct gendisk *disk = rdev->bdev->bd_disk;
> + if (!mddev_is_dm(mddev)) {
> + unsigned long last_events = mddev->last_events;
>
> - if (!init && !blk_queue_io_stat(disk->queue))
> - continue;
> + mddev->last_events = part_stat_read_accum(mddev->gendisk->part0,
> + sectors);
>
> - curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
> - atomic_read(&disk->sync_io);
> - /* sync IO will cause sync_io to increase before the disk_stats
> - * as sync_io is counted when a request starts, and
> - * disk_stats is counted when it completes.
> - * So resync activity will cause curr_events to be smaller than
> - * when there was no such activity.
> - * non-sync IO will cause disk_stat to increase without
> - * increasing sync_io so curr_events will (eventually)
> - * be larger than it was before. Once it becomes
> - * substantially larger, the test below will cause
> - * the array to appear non-idle, and resync will slow
> - * down.
> - * If there is a lot of outstanding resync activity when
> - * we set last_event to curr_events, then all that activity
> - * completing might cause the array to appear non-idle
> - * and resync will be slowed down even though there might
> - * not have been non-resync activity. This will only
> - * happen once though. 'last_events' will soon reflect
> - * the state where there is little or no outstanding
> - * resync requests, and further resync activity will
> - * always make curr_events less than last_events.
> - *
> - */
> - if (init || curr_events - rdev->last_events > 64) {
> - rdev->last_events = curr_events;
> - idle = 0;
> - }
> + if (!init && (mddev->last_events > last_events ||
> + part_in_flight(mddev->gendisk->part0)))
> + idle = false;
> }
> +
> + rcu_read_lock();
> + rdev_for_each_rcu(rdev, mddev)
> + if (!is_rdev_idle(rdev, init))
> + idle = false;
> rcu_read_unlock();
> +
> return idle;
> }
>
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 63be622467c6..95cf11c4abc6 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -132,7 +132,7 @@ struct md_rdev {
>
> sector_t sectors; /* Device size (in 512bytes sectors) */
> struct mddev *mddev; /* RAID array if running */
> - int last_events; /* IO event timestamp */
> + unsigned long last_events; /* IO event timestamp */
>
> /*
> * If meta_bdev is non-NULL, it means that a separate device is
> @@ -519,6 +519,7 @@ struct mddev {
> * adding a spare
> */
>
> + unsigned long last_events; /* IO event timestamp */
> atomic_t recovery_active; /* blocks scheduled, but not written */
> wait_queue_head_t recovery_wait;
> sector_t recovery_cp;
Powered by blists - more mailing lists