linux-kernel - Re: linux-next: manual merge of the userns tree with the cel tree

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Message-ID: <20211217174853.752c032f@canb.auug.org.au>
Date:   Fri, 17 Dec 2021 17:48:53 +1100
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     "Eric W . Biederman" <ebiederm@...ssion.com>,
        Chuck Lever <chuck.lever@...cle.com>
Cc:     broonie@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        NeilBrown <neilb@...e.de>
Subject: Re: linux-next: manual merge of the userns tree with the cel tree

Hi all,

On Thu, 16 Dec 2021 19:34:12 +0000 broonie@...nel.org wrote:
>
> Today's linux-next merge of the userns tree got a conflict in:
> 
>   fs/nfsd/nfssvc.c
> 
> between commit:
> 
>   cfb05a7336741 ("NFSD: narrow nfsd_mutex protection in nfsd thread")

This is now commit 9d3792aefdcd

> from the cel tree and commit:
> 
>   ca3574bd653ab ("exit: Rename module_put_and_exit to module_put_and_kthread_exit")
> 
> from the userns tree.
> 
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging.  You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
> 
> diff --cc fs/nfsd/nfssvc.c
> index 14c1ef6f8cc74,5ce9f14318c4e..0000000000000
> --- a/fs/nfsd/nfssvc.c
> +++ b/fs/nfsd/nfssvc.c
> @@@ -977,25 -982,11 +977,25 @@@ out
>   	/* Release the thread */
>   	svc_exit_thread(rqstp);
>   
>  -	nfsd_destroy(net);
>  +	/* We need to drop a ref, but may not drop the last reference
>  +	 * without holding nfsd_mutex, and we cannot wait for nfsd_mutex as that
>  +	 * could deadlock with nfsd_shutdown_threads() waiting for us.
>  +	 * So three options are:
>  +	 * - drop a non-final reference,
>  +	 * - get the mutex without waiting
>  +	 * - sleep briefly andd try the above again
>  +	 */
>  +	while (!svc_put_not_last(nn->nfsd_serv)) {
>  +		if (mutex_trylock(&nfsd_mutex)) {
>  +			nfsd_put(net);
>  +			mutex_unlock(&nfsd_mutex);
>  +			break;
>  +		}
>  +		msleep(20);
>  +	}
>   
>   	/* Release module */
> - 	module_put_and_exit(0);
>  -	mutex_unlock(&nfsd_mutex);
> + 	module_put_and_kthread_exit(0);
>   	return 0;
>   }
>   

-- 
Cheers,
Stephen Rothwell

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