Re: [PATCH md-6.10 3/9] md: add new helpers for sync_action

[Yu Kuai]

Hi,

在 2024/05/20 19:51, Su Yue 写道:
> On Thu 09 May 2024 at 09:18, Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:
>
> > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > ---
> >  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]

Yes, this make sense.
> > +    [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...
> I agree with Xiao Ni's suggestion that more comments about the array
> state should be added.

Okay, perhaps you're refering md_is_rdwr()? which is supposed to be
related to "no new sync_thread is requestd", perhaps following is
better:

/* only read-write array can start sync_thread */
if (!(md_is_rdwr(mddev))
	return ACTION_IDLE;

/* sync_thread is not running, and no new sync_thread is requested */
if (!test_bit(MD_RECOVERY_RUNNING, &recovery) &&
    !test_bit(MD_RECOVERY_NEEDED, &recovery)
	return ACTION_IDLE;

> > +    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.

It's just because MD_RECOVERY_SYNC is more complicated, and I move it to
the last, just programming habits. :)
> > +    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 *'

Yes

Thanks,
Kuai

> --
> 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);
> .