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

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Message-ID: <v838ekaa.fsf@damenly.org>
Date: Mon, 20 May 2024 19:51:25 +0800
From: Su Yue <l@...enly.org>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: agk@...hat.com, snitzer@...nel.org, mpatocka@...hat.com,
 song@...nel.org, xni@...hat.com, 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 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...
I agree with Xiao Ni's suggestion that more comments about the 
array
state should be added.

> +	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);