linux-kernel - Re: [PATCH v3 06/16] rbd: convert timeouts to secs_to

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Message-ID: <e53d7586-b278-4338-95a2-fa768d5d8b5e@wanadoo.fr>
Date: Tue, 25 Feb 2025 22:09:55 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Easwar Hariharan <eahariha@...ux.microsoft.com>
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Subject: Re: [PATCH v3 06/16] rbd: convert timeouts to secs_to_jiffies()

Le 25/02/2025 à 21:17, Easwar Hariharan a écrit :
> Commit b35108a51cf7 ("jiffies: Define secs_to_jiffies()") introduced
> secs_to_jiffies().  As the value here is a multiple of 1000, use
> secs_to_jiffies() instead of msecs_to_jiffies() to avoid the multiplication
> 
> This is converted using scripts/coccinelle/misc/secs_to_jiffies.cocci with
> the following Coccinelle rules:
> 
> @depends on patch@ expression E; @@
> 
> -msecs_to_jiffies(E * 1000)
> +secs_to_jiffies(E)
> 
> @depends on patch@ expression E; @@
> 
> -msecs_to_jiffies(E * MSEC_PER_SEC)
> +secs_to_jiffies(E)
> 
> While here, remove the no-longer necessary check for range since there's
> no multiplication involved.

I'm not sure this is correct.
Now you multiply by HZ and things can still overflow.


Hoping I got casting right:

#define MSEC_PER_SEC	1000L
#define HZ 100


#define secs_to_jiffies(_secs) (unsigned long)((_secs) * HZ)

static inline unsigned long _msecs_to_jiffies(const unsigned int m)
{
	return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
}

int main() {

	int n = INT_MAX - 5;

	printf("res  = %ld\n", secs_to_jiffies(n));
	printf("res  = %ld\n", _msecs_to_jiffies(1000 * n));

	return 0;
}


gives :

res  = -600
res  = 429496130

with msec, the previous code would catch the overflow, now it overflows 
silently.

untested, but maybe:
	if (result.uint_32 > INT_MAX / HZ)
		goto out_of_range;

?

CJ


> 
> Acked-by: Ilya Dryomov <idryomov-Re5JQEeQqe8AvxtiuMwx3w@...lic.gmane.org>
> Signed-off-by: Easwar Hariharan <eahariha-1pm0nblsJy7Jp67UH1NAhkEOCMrvLtNR@...lic.gmane.org>
> ---
>   drivers/block/rbd.c | 8 +++-----
>   1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index faafd7ff43d6ef53110ab3663cc7ac322214cc8c..41207133e21e9203192adf3b92390818e8fa5a58 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -108,7 +108,7 @@ static int atomic_dec_return_safe(atomic_t *v)
>   #define RBD_OBJ_PREFIX_LEN_MAX	64
>   
>   #define RBD_NOTIFY_TIMEOUT	5	/* seconds */
> -#define RBD_RETRY_DELAY		msecs_to_jiffies(1000)
> +#define RBD_RETRY_DELAY		secs_to_jiffies(1)
>   
>   /* Feature bits */
>   
> @@ -4162,7 +4162,7 @@ static void rbd_acquire_lock(struct work_struct *work)
>   		dout("%s rbd_dev %p requeuing lock_dwork\n", __func__,
>   		     rbd_dev);
>   		mod_delayed_work(rbd_dev->task_wq, &rbd_dev->lock_dwork,
> -		    msecs_to_jiffies(2 * RBD_NOTIFY_TIMEOUT * MSEC_PER_SEC));
> +		    secs_to_jiffies(2 * RBD_NOTIFY_TIMEOUT));
>   	}
>   }
>   
> @@ -6283,9 +6283,7 @@ static int rbd_parse_param(struct fs_parameter *param,
>   		break;
>   	case Opt_lock_timeout:
>   		/* 0 is "wait forever" (i.e. infinite timeout) */
> -		if (result.uint_32 > INT_MAX / 1000)
> -			goto out_of_range;
> -		opt->lock_timeout = msecs_to_jiffies(result.uint_32 * 1000);
> +		opt->lock_timeout = secs_to_jiffies(result.uint_32);
>   		break;
>   	case Opt_pool_ns:
>   		kfree(pctx->spec->pool_ns);
>