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Subject: Re: [PATCH md-6.9 02/10] md: record nonrot rdevs while
 adding/removing rdevs to conf
To: Xiao Ni <xni@redhat.com>, Yu Kuai <yukuai1@huaweicloud.com>
Cc: paul.e.luse@linux.intel.com, song@kernel.org, neilb@suse.com,
 shli@fb.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
 yi.zhang@huawei.com, yangerkun@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
References: <20240222075806.1816400-1-yukuai1@huaweicloud.com>
 <20240222075806.1816400-3-yukuai1@huaweicloud.com>
 <CALTww28nOniYZDV9Kpaymze=Ph+EKSwrr+2QMo2WQsR3hKvD_A@mail.gmail.com>
From: Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <32521aa2-876e-0e87-975b-34ff00f9095c@huaweicloud.com>
Date: Mon, 26 Feb 2024 21:25:17 +0800
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Hi,

在 2024/02/26 21:12, Xiao Ni 写道:
> Hi Kuai
> 
> I added some logs to check and add_bound_rdev can't be called when
> creating raid device. Maybe move rdev_update_nonrot to
> bind_rdev_to_array?

bind_rdev_to_array() is used to add new rdev to the array, then
'pers->hot_add_disk' is used to add the rdev to conf. For new spares,
bind_rdev_to_array() will be called while 'pers->hot_add_disk' won't.
Hence rdev_update_nonrot() is used where 'pers->hot_add_disk' succeed
in this patch.

Perhaps it's better to move related code to raid1/raid10_add_disk() and
the new counter in raid1/raid10 conf?

Thanks,
Kuai

> 
> Regards
> Xiao
> 
> On Thu, Feb 22, 2024 at 4:04 PM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>>
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> For raid1/raid10, each read will iterate all the rdevs from conf and
>> check if any rdev is non-rotational, then choose rdev with minimal IO
>> inflight if so, or rdev with closest distance otherwise.
>>
>> Disk nonrot info can be changed through sysfs entry:
>>
>> /sys/block/[disk_name]/queue/rotational
>>
>> However, consider that this should only be used for testing, and user
>> really shouldn't do this in real life. Record the number of non-rotational
>> disks in mddev, to avoid checking each rdev in IO fast path and simplify
>> read_balance() a little bit.
>>
>> Co-developed-by: Paul Luse <paul.e.luse@linux.intel.com>
>> Signed-off-by: Paul Luse <paul.e.luse@linux.intel.com>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>> ---
>>   drivers/md/md.c     | 28 ++++++++++++++++++++++++++--
>>   drivers/md/md.h     |  2 ++
>>   drivers/md/raid1.c  |  9 ++-------
>>   drivers/md/raid10.c |  8 ++------
>>   4 files changed, 32 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index e2a5f513dbb7..9e671eec9309 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -146,6 +146,24 @@ static inline int speed_max(struct mddev *mddev)
>>                  mddev->sync_speed_max : sysctl_speed_limit_max;
>>   }
>>
>> +static void rdev_update_nonrot(struct md_rdev *rdev)
>> +{
>> +       if (!bdev_nonrot(rdev->bdev))
>> +               return;
>> +
>> +       set_bit(Nonrot, &rdev->flags);
>> +       WRITE_ONCE(rdev->mddev->nonrot_disks, rdev->mddev->nonrot_disks + 1);
>> +}
>> +
>> +static void rdev_clear_nonrot(struct md_rdev *rdev)
>> +{
>> +       if (!test_bit(Nonrot, &rdev->flags))
>> +               return;
>> +
>> +       clear_bit(Nonrot, &rdev->flags);
>> +       WRITE_ONCE(rdev->mddev->nonrot_disks, rdev->mddev->nonrot_disks - 1);
>> +}
>> +
>>   static void rdev_uninit_serial(struct md_rdev *rdev)
>>   {
>>          if (!test_and_clear_bit(CollisionCheck, &rdev->flags))
>> @@ -2922,6 +2940,8 @@ static int add_bound_rdev(struct md_rdev *rdev)
>>                          md_kick_rdev_from_array(rdev);
>>                          return err;
>>                  }
>> +
>> +               rdev_update_nonrot(rdev);
>>          }
>>          sysfs_notify_dirent_safe(rdev->sysfs_state);
>>
>> @@ -3271,8 +3291,10 @@ slot_store(struct md_rdev *rdev, const char *buf, size_t len)
>>                  if (err) {
>>                          rdev->raid_disk = -1;
>>                          return err;
>> -               } else
>> -                       sysfs_notify_dirent_safe(rdev->sysfs_state);
>> +               }
>> +
>> +               rdev_update_nonrot(rdev);
>> +               sysfs_notify_dirent_safe(rdev->sysfs_state);
>>                  /* failure here is OK */;
>>                  sysfs_link_rdev(rdev->mddev, rdev);
>>                  /* don't wakeup anyone, leave that to userspace. */
>> @@ -9266,6 +9288,7 @@ static int remove_and_add_spares(struct mddev *mddev,
>>          rdev_for_each(rdev, mddev) {
>>                  if ((this == NULL || rdev == this) && rdev_removeable(rdev) &&
>>                      !mddev->pers->hot_remove_disk(mddev, rdev)) {
>> +                       rdev_clear_nonrot(rdev);
>>                          sysfs_unlink_rdev(mddev, rdev);
>>                          rdev->saved_raid_disk = rdev->raid_disk;
>>                          rdev->raid_disk = -1;
>> @@ -9289,6 +9312,7 @@ static int remove_and_add_spares(struct mddev *mddev,
>>                  if (!test_bit(Journal, &rdev->flags))
>>                          rdev->recovery_offset = 0;
>>                  if (mddev->pers->hot_add_disk(mddev, rdev) == 0) {
>> +                       rdev_update_nonrot(rdev);
>>                          /* failure here is OK */
>>                          sysfs_link_rdev(mddev, rdev);
>>                          if (!test_bit(Journal, &rdev->flags))
>> diff --git a/drivers/md/md.h b/drivers/md/md.h
>> index a49ab04ab707..54aa951f2bba 100644
>> --- a/drivers/md/md.h
>> +++ b/drivers/md/md.h
>> @@ -207,6 +207,7 @@ enum flag_bits {
>>                                   * check if there is collision between raid1
>>                                   * serial bios.
>>                                   */
>> +       Nonrot,                 /* non-rotational device (SSD) */
>>   };
>>
>>   static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
>> @@ -312,6 +313,7 @@ struct mddev {
>>          unsigned long                   flags;
>>          unsigned long                   sb_flags;
>>
>> +       int                             nonrot_disks;
>>          int                             suspended;
>>          struct mutex                    suspend_mutex;
>>          struct percpu_ref               active_io;
>> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
>> index a145fe48b9ce..c60ea58ae8c5 100644
>> --- a/drivers/md/raid1.c
>> +++ b/drivers/md/raid1.c
>> @@ -599,7 +599,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
>>          int sectors;
>>          int best_good_sectors;
>>          int best_disk, best_dist_disk, best_pending_disk;
>> -       int has_nonrot_disk;
>>          int disk;
>>          sector_t best_dist;
>>          unsigned int min_pending;
>> @@ -620,7 +619,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
>>          best_pending_disk = -1;
>>          min_pending = UINT_MAX;
>>          best_good_sectors = 0;
>> -       has_nonrot_disk = 0;
>>          choose_next_idle = 0;
>>          clear_bit(R1BIO_FailFast, &r1_bio->state);
>>
>> @@ -637,7 +635,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
>>                  sector_t first_bad;
>>                  int bad_sectors;
>>                  unsigned int pending;
>> -               bool nonrot;
>>
>>                  rdev = conf->mirrors[disk].rdev;
>>                  if (r1_bio->bios[disk] == IO_BLOCKED
>> @@ -703,8 +700,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
>>                          /* At least two disks to choose from so failfast is OK */
>>                          set_bit(R1BIO_FailFast, &r1_bio->state);
>>
>> -               nonrot = bdev_nonrot(rdev->bdev);
>> -               has_nonrot_disk |= nonrot;
>>                  pending = atomic_read(&rdev->nr_pending);
>>                  dist = abs(this_sector - conf->mirrors[disk].head_position);
>>                  if (choose_first) {
>> @@ -731,7 +726,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
>>                           * small, but not a big deal since when the second disk
>>                           * starts IO, the first disk is likely still busy.
>>                           */
>> -                       if (nonrot && opt_iosize > 0 &&
>> +                       if (test_bit(Nonrot, &rdev->flags) && opt_iosize > 0 &&
>>                              mirror->seq_start != MaxSector &&
>>                              mirror->next_seq_sect > opt_iosize &&
>>                              mirror->next_seq_sect - opt_iosize >=
>> @@ -763,7 +758,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
>>           * mixed ratation/non-rotational disks depending on workload.
>>           */
>>          if (best_disk == -1) {
>> -               if (has_nonrot_disk || min_pending == 0)
>> +               if (conf->mddev->nonrot_disks || min_pending == 0)
>>                          best_disk = best_pending_disk;
>>                  else
>>                          best_disk = best_dist_disk;
>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
>> index d5a7a621f0f0..1f6693e40e12 100644
>> --- a/drivers/md/raid10.c
>> +++ b/drivers/md/raid10.c
>> @@ -735,7 +735,6 @@ static struct md_rdev *read_balance(struct r10conf *conf,
>>          struct md_rdev *best_dist_rdev, *best_pending_rdev, *rdev = NULL;
>>          int do_balance;
>>          int best_dist_slot, best_pending_slot;
>> -       bool has_nonrot_disk = false;
>>          unsigned int min_pending;
>>          struct geom *geo = &conf->geo;
>>
>> @@ -766,7 +765,6 @@ static struct md_rdev *read_balance(struct r10conf *conf,
>>                  int bad_sectors;
>>                  sector_t dev_sector;
>>                  unsigned int pending;
>> -               bool nonrot;
>>
>>                  if (r10_bio->devs[slot].bio == IO_BLOCKED)
>>                          continue;
>> @@ -818,10 +816,8 @@ static struct md_rdev *read_balance(struct r10conf *conf,
>>                  if (!do_balance)
>>                          break;
>>
>> -               nonrot = bdev_nonrot(rdev->bdev);
>> -               has_nonrot_disk |= nonrot;
>>                  pending = atomic_read(&rdev->nr_pending);
>> -               if (min_pending > pending && nonrot) {
>> +               if (min_pending > pending && test_bit(Nonrot, &rdev->flags)) {
>>                          min_pending = pending;
>>                          best_pending_slot = slot;
>>                          best_pending_rdev = rdev;
>> @@ -851,7 +847,7 @@ static struct md_rdev *read_balance(struct r10conf *conf,
>>                  }
>>          }
>>          if (slot >= conf->copies) {
>> -               if (has_nonrot_disk) {
>> +               if (conf->mddev->nonrot_disks) {
>>                          slot = best_pending_slot;
>>                          rdev = best_pending_rdev;
>>                  } else {
>> --
>> 2.39.2
>>
>>
> 
> .
>