linux-kernel - Re: [PATCH v5] PM: Support aborting sleep during filesystem sync

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Message-ID: <20251018001715.8621-1-hdanton@sina.com>
Date: Sat, 18 Oct 2025 08:17:12 +0800
From: Hillf Danton <hdanton@...a.com>
To: Samuel Wu <wusamuel@...gle.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Pavel Machek <pavel@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Danilo Krummrich <dakr@...nel.org>
Cc: Saravana Kannan <saravanak@...gle.com>,
	kernel-team@...roid.com,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] PM: Support aborting sleep during filesystem sync

On Fri, 17 Oct 2025 23:39:06 +0000 Samuel Wu wrote:
> +/**
> + * pm_sleep_fs_sync - Trigger fs_sync with ability to abort
> + *
> + * Return 0 on successful file system sync, otherwise returns -EBUSY if file
> + * system sync was aborted.
> + */
> +int pm_sleep_fs_sync(void)
> +{
> +	bool need_pm_sleep_fs_sync_requeue;
> +	unsigned long flags;
> +
> +	do {
> +		spin_lock_irqsave(&pm_sleep_fs_sync_lock, flags);
> +		reinit_completion(&pm_sleep_fs_sync_complete);

Given difficulty following up here, can you specify why reinit is needed?
> +		/*
> +		 * Handle the case where a sleep immediately follows a previous
> +		 * sleep that was aborted during fs_sync. In this case, wait for
> +		 * the previous filesystem sync to finish. Then do another
> +		 * filesystem sync so any subsequent filesystem changes are
> +		 * synced before sleeping.
> +		 */
> +		if (pm_sleep_fs_sync_queued) {
> +			need_pm_sleep_fs_sync_requeue = true;
> +		} else {
> +			need_pm_sleep_fs_sync_requeue = false;
> +			pm_sleep_fs_sync_queued = true;
> +			schedule_work(&sync_filesystems);
> +		}
> +		spin_unlock_irqrestore(&pm_sleep_fs_sync_lock, flags);
> +
> +		/*
> +		 * Completion is triggered by fs_sync finishing or an abort sleep
> +		 * signal, whichever comes first
> +		 */
> +		wait_for_completion(&pm_sleep_fs_sync_complete);
> +		if (pm_wakeup_pending())
> +			return -EBUSY;
> +	} while (need_pm_sleep_fs_sync_requeue);
> +
> +	return 0;
> +}
> +