linux-kernel - Re: [PATCH] xfs: Drop setting redundant PF

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Message-ID: <20170824105635.GA5965@dhcp22.suse.cz>
Date:   Thu, 24 Aug 2017 12:56:35 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:     linux-mm@...ck.org, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, dchinner@...hat.com,
        bfoster@...hat.com, sandeen@...deen.net
Subject: Re: [PATCH] xfs: Drop setting redundant PF_KSWAPD in kswapd context

On Thu 24-08-17 16:12:47, Anshuman Khandual wrote:
> xfs_btree_split() calls xfs_btree_split_worker() with args.kswapd set
> if current->flags alrady has PF_KSWAPD. Hence we should not again add
> PF_KSWAPD into the current flags inside kswapd context. So drop this
> redundant flag addition.

I am not familiar with the code but your change seems incorect. The
whole point of args->kswapd is to convey the kswapd context to the
worker which is obviously running in a different context. So this patch
loses the kswapd context.

> Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
> ---
>  fs/xfs/libxfs/xfs_btree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> index e0bcc4a..b3c85e3 100644
> --- a/fs/xfs/libxfs/xfs_btree.c
> +++ b/fs/xfs/libxfs/xfs_btree.c
> @@ -2895,7 +2895,7 @@ struct xfs_btree_split_args {
>  	 * in any way.
>  	 */
>  	if (args->kswapd)
> -		new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
> +		new_pflags |= PF_MEMALLOC | PF_SWAPWRITE;
>  
>  	current_set_flags_nested(&pflags, new_pflags);
>  
> -- 
> 1.8.5.2

-- 
Michal Hocko
SUSE Labs