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In-Reply-To: <06211ae2-9b5f-10c7-7953-9d79d2eacc67@huaweicloud.com>
From: Xiao Ni <xni@redhat.com>
Date: Tue, 14 May 2024 16:40:28 +0800
Message-ID: <CALTww28LM_b6SMC-vLY3y7R3ZD9z80H+2vZCXMzmAwnoEH-eMA@mail.gmail.com>
Subject: Re: [PATCH md-6.10 3/9] md: add new helpers for sync_action
To: Yu Kuai <yukuai1@huaweicloud.com>
Cc: agk@redhat.com, snitzer@kernel.org, mpatocka@redhat.com, song@kernel.org, 
	dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org, 
	linux-raid@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, 
	"yukuai (C)" <yukuai3@huawei.com>
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On Tue, May 14, 2024 at 3:39=E2=80=AFPM Yu Kuai <yukuai1@huaweicloud.com> w=
rote:
>
> Hi,
>
> =E5=9C=A8 2024/05/14 14:52, Xiao Ni =E5=86=99=E9=81=93:
> > On Mon, May 13, 2024 at 5:31=E2=80=AFPM Yu Kuai <yukuai1@huaweicloud.co=
m> wrote:
> >>
> >> From: Yu Kuai <yukuai3@huawei.com>
> >>
> >> The new helpers will get current sync_action of the array, will be use=
d
> >> in later patches to make code cleaner.
> >>
> >> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> >> ---
> >>   drivers/md/md.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++=
++
> >>   drivers/md/md.h |  3 +++
> >>   2 files changed, 67 insertions(+)
> >>
> >> diff --git a/drivers/md/md.c b/drivers/md/md.c
> >> index 00bbafcd27bb..48ec35342d1b 100644
> >> --- a/drivers/md/md.c
> >> +++ b/drivers/md/md.c
> >> @@ -69,6 +69,16 @@
> >>   #include "md-bitmap.h"
> >>   #include "md-cluster.h"
> >>
> >> +static char *action_name[NR_SYNC_ACTIONS] =3D {
> >> +       [ACTION_RESYNC]         =3D "resync",
> >> +       [ACTION_RECOVER]        =3D "recover",
> >> +       [ACTION_CHECK]          =3D "check",
> >> +       [ACTION_REPAIR]         =3D "repair",
> >> +       [ACTION_RESHAPE]        =3D "reshape",
> >> +       [ACTION_FROZEN]         =3D "frozen",
> >> +       [ACTION_IDLE]           =3D "idle",
> >> +};
> >> +
> >>   /* pers_list is a list of registered personalities protected by pers=
_lock. */
> >>   static LIST_HEAD(pers_list);
> >>   static DEFINE_SPINLOCK(pers_lock);
> >> @@ -4867,6 +4877,60 @@ metadata_store(struct mddev *mddev, const char =
*buf, size_t len)
> >>   static struct md_sysfs_entry md_metadata =3D
> >>   __ATTR_PREALLOC(metadata_version, S_IRUGO|S_IWUSR, metadata_show, me=
tadata_store);
> >>
> >> +enum sync_action md_sync_action(struct mddev *mddev)
> >> +{
> >> +       unsigned long recovery =3D mddev->recovery;
> >> +
> >> +       /*
> >> +        * frozen has the highest priority, means running sync_thread =
will be
> >> +        * stopped immediately, and no new sync_thread can start.
> >> +        */
> >> +       if (test_bit(MD_RECOVERY_FROZEN, &recovery))
> >> +               return ACTION_FROZEN;
> >> +
> >> +       /*
> >> +        * idle means no sync_thread is running, and no new sync_threa=
d is
> >> +        * requested.
> >> +        */
> >> +       if (!test_bit(MD_RECOVERY_RUNNING, &recovery) &&
> >> +           (!md_is_rdwr(mddev) || !test_bit(MD_RECOVERY_NEEDED, &reco=
very)))
> >> +               return ACTION_IDLE;
> >
> > Hi Kuai
> >
> > Can I think the above judgement cover these two situations:
> > 1. The array is readonly / readauto and it doesn't have
> > MD_RECOVERY_RUNNING. Now maybe it has MD_RECOVERY_NEEDED, it means one
> > array may want to do some sync action, but the array state is not
> > readwrite and it can't start.
> > 2. The array doesn't have MD_RECOVERY_RUNNING and MD_RECOVERY_NEEDED
> >
> >> +
> >> +       if (test_bit(MD_RECOVERY_RESHAPE, &recovery) ||
> >> +           mddev->reshape_position !=3D MaxSector)
> >> +               return ACTION_RESHAPE;
> >> +
> >> +       if (test_bit(MD_RECOVERY_RECOVER, &recovery))
> >> +               return ACTION_RECOVER;
> >> +
> >> +       if (test_bit(MD_RECOVERY_SYNC, &recovery)) {
> >> +               if (test_bit(MD_RECOVERY_CHECK, &recovery))
> >> +                       return ACTION_CHECK;
> >> +               if (test_bit(MD_RECOVERY_REQUESTED, &recovery))
> >> +                       return ACTION_REPAIR;
> >> +               return ACTION_RESYNC;
> >> +       }
> >> +
> >> +       return ACTION_IDLE;
> >
> > Does it need this? I guess it's the reason in case there are other
> > situations, right?
>
> Yes, we need this, because they are many places to set
> MD_RECOVERY_NEEDED, while there are no sync action actually, this case
> is 'idle'.

To be frank, the logic in action_show is easier to understand than the
logic above. I have taken more than half an hour to think if the logic
here is right or not. In action_show, it only needs to think when it's
not idle and it's easy.

Now this patch logic needs to think in the opposite direction: when
it's idle. And it returns ACTION_IDLE at two places which means it
still needs to think about when it has sync action. So it's better to
keep the original logic in action_show now. It's just my 2 cents
point.

Best Regards
Xiao

>
> Thanks,
> Kuai
>
> >
> > Regards
> > Xiao
> >
> >> +}
> >> +
> >> +enum sync_action md_sync_action_by_name(char *page)
> >> +{
> >> +       enum sync_action action;
> >> +
> >> +       for (action =3D 0; action < NR_SYNC_ACTIONS; ++action) {
> >> +               if (cmd_match(page, action_name[action]))
> >> +                       return action;
> >> +       }
> >> +
> >> +       return NR_SYNC_ACTIONS;
> >> +}
> >> +
> >> +char *md_sync_action_name(enum sync_action action)
> >> +{
> >> +       return action_name[action];
> >> +}
> >> +
> >>   static ssize_t
> >>   action_show(struct mddev *mddev, char *page)
> >>   {
> >> diff --git a/drivers/md/md.h b/drivers/md/md.h
> >> index 2edad966f90a..72ca7a796df5 100644
> >> --- a/drivers/md/md.h
> >> +++ b/drivers/md/md.h
> >> @@ -864,6 +864,9 @@ extern void md_unregister_thread(struct mddev *mdd=
ev, struct md_thread __rcu **t
> >>   extern void md_wakeup_thread(struct md_thread __rcu *thread);
> >>   extern void md_check_recovery(struct mddev *mddev);
> >>   extern void md_reap_sync_thread(struct mddev *mddev);
> >> +extern enum sync_action md_sync_action(struct mddev *mddev);
> >> +extern enum sync_action md_sync_action_by_name(char *page);
> >> +extern char *md_sync_action_name(enum sync_action action);
> >>   extern bool md_write_start(struct mddev *mddev, struct bio *bi);
> >>   extern void md_write_inc(struct mddev *mddev, struct bio *bi);
> >>   extern void md_write_end(struct mddev *mddev);
> >> --
> >> 2.39.2
> >>
> >
> > .
> >
>
>