linux-kernel - Re: [PATCH md-6.10 3/9] md: add new helpers for sync

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Date: Tue, 21 May 2024 11:25:31 +0800
From: Xiao Ni <xni@...hat.com>
To: Su Yue <l@...enly.org>
Cc: Yu Kuai <yukuai1@...weicloud.com>, agk@...hat.com, snitzer@...nel.org, 
	mpatocka@...hat.com, song@...nel.org, dm-devel@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org, yukuai3@...wei.com, 
	yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH md-6.10 3/9] md: add new helpers for sync_action

On Mon, May 20, 2024 at 8:38 PM Su Yue <l@...enly.org> wrote:
>
>
> On Thu 09 May 2024 at 09:18, Yu Kuai <yukuai1@...weicloud.com>
> wrote:
>
> > From: Yu Kuai <yukuai3@...wei.com>
> >
> > The new helpers will get current sync_action of the array, will
> > be used
> > in later patches to make code cleaner.
> >
> > Signed-off-by: Yu Kuai <yukuai3@...wei.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] = {
> >
>
> Th array will not be modified, so:
>
> static const char * const action_names[NR_SYNC_ACTIONS]
>
> > +     [ACTION_RESYNC]         = "resync",
> > +     [ACTION_RECOVER]        = "recover",
> > +     [ACTION_CHECK]          = "check",
> > +     [ACTION_REPAIR]         = "repair",
> > +     [ACTION_RESHAPE]        = "reshape",
> > +     [ACTION_FROZEN]         = "frozen",
> > +     [ACTION_IDLE]           = "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 =
> >  __ATTR_PREALLOC(metadata_version, S_IRUGO|S_IWUSR,
> >  metadata_show, metadata_store);
> >
> > +enum sync_action md_sync_action(struct mddev *mddev)
> > +{
> > +     unsigned long recovery = 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_thread is
> > +      * requested.
> > +      */
> > +     if (!test_bit(MD_RECOVERY_RUNNING, &recovery) &&
> > +         (!md_is_rdwr(mddev) || !test_bit(MD_RECOVERY_NEEDED,
> > &recovery)))
> > +             return ACTION_IDLE;
> My brain was lost sometimes looking into nested conditions of md
> code...

agree+

> I agree with Xiao Ni's suggestion that more comments about the
> array
> state should be added.

In fact, I suggest to keep the logic which is in action_show now. The
logic in action_show is easier to understand for me.

Best Regards
Xiao
>
> > +     if (test_bit(MD_RECOVERY_RESHAPE, &recovery) ||
> > +         mddev->reshape_position != MaxSector)
> > +             return ACTION_RESHAPE;
> > +
> > +     if (test_bit(MD_RECOVERY_RECOVER, &recovery))
> > +             return ACTION_RECOVER;
> > +
> >
> In action_show, MD_RECOVERY_SYNC is tested first then
> MD_RECOVERY_RECOVER.
> After looking through the logic of MD_RECOVERY_RECOVER
> clear/set_bit, the
> change is fine to me. However, better to follow old pattern unless
> there
> have resons.
>
>
> > +     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;
> > +}
> > +
> > +enum sync_action md_sync_action_by_name(char *page)
> > +{
> > +     enum sync_action action;
> > +
> > +     for (action = 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)
> >
>
> And 'const char *'
>
> --
> Su
>
> > +{
> > +     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 *mddev, 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);
>