linux-kernel - Re: [PATCH] [fuse] alloc

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Date:   Thu, 3 Jun 2021 14:56:12 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     chenguanyou <chenguanyou9338@...il.com>
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        keescook@...omium.org, lukas.bulwahn@...il.com, vbabka@...e.cz,
        gpiccoli@...onical.com, chenguanyou <chenguanyou@...omi.com>
Subject: Re: [PATCH] [fuse] alloc_page nofs avoid deadlock

On Thu 03-06-21 20:41:05, chenguanyou wrote:
> ABA deadlock
> 
> PID: 17172 TASK: ffffffc0c162c000 CPU: 6 COMMAND: "Thread-21"
> 
> PID: 9652 TASK: ffffffc0c9ce0000 CPU: 4 COMMAND: "kworker/u16:8"

Please be much more specific about the underlying issue and what the
actual lock dependency during the reclaim is. The above is essentially
void of any relevant information.

> Signed-off-by: chenguanyou <chenguanyou@...omi.com>
> ---
>  fs/fuse/dev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index c0fee830a34e..d36125ff0405 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -721,7 +721,7 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
>  			if (cs->nr_segs >= cs->pipe->max_usage)
>  				return -EIO;
>  
> -			page = alloc_page(GFP_HIGHUSER);
> +			page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
>  			if (!page)
>  				return -ENOMEM;
>  
> -- 
> 2.17.1

-- 
Michal Hocko
SUSE Labs