linux-kernel - Re: [PATCH] swapfile: initialize spinlock for swap_cluster

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Date:   Tue, 07 Feb 2017 10:52:57 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Huang Ying <ying.huang@...el.com>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] swapfile: initialize spinlock for swap_cluster_info

Hi, Minchan,

Minchan Kim <minchan@...nel.org> writes:

> We changed swap_cluster_info lock from bit_spin_lock to spinlock
> so we need to initialize the spinlock before the using. Otherwise,
> lockdep is broken.
>
> Cc: Tim Chen <tim.c.chen@...ux.intel.com>
> Cc: Huang Ying <ying.huang@...el.com>
> Cc: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>

Good catch!  Thanks a lot for your fixing!

Reviewed-by: "Huang, Ying" <ying.huang@...el.com>

Best Regards,
Huang, Ying

> ---
> Andrew,
> I think it's no worth to add this patch to separate commit.
> If you don't mind, it's okay to fold this patch to mm-swap-add-cluster-lock-v5.
> Thanks.
>
>  mm/swapfile.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 1fc1824140e1..5ac2cb40dbd3 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2762,6 +2762,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
>  
>  	if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
>  		int cpu;
> +		unsigned long ci, nr_cluster;
>  
>  		p->flags |= SWP_SOLIDSTATE;
>  		/*
> @@ -2769,13 +2770,17 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
>  		 * SSD
>  		 */
>  		p->cluster_next = 1 + (prandom_u32() % p->highest_bit);
> +		nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
>  
> -		cluster_info = vzalloc(DIV_ROUND_UP(maxpages,
> -			SWAPFILE_CLUSTER) * sizeof(*cluster_info));
> +		cluster_info = vzalloc(nr_cluster * sizeof(*cluster_info));
>  		if (!cluster_info) {
>  			error = -ENOMEM;
>  			goto bad_swap;
>  		}
> +
> +		for (ci = 0; ci < nr_cluster; ci++)
> +			spin_lock_init(&((cluster_info + ci)->lock));
> +
>  		p->percpu_cluster = alloc_percpu(struct percpu_cluster);
>  		if (!p->percpu_cluster) {
>  			error = -ENOMEM;