linux-kernel - Re: [PATCH] lockd: convert reclaimer thread to kthread interface

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Date:	Mon, 3 Nov 2008 13:12:15 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	trond.myklebust@....uio.no, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, hch@...radead.org
Subject: Re: [PATCH] lockd: convert reclaimer thread to kthread interface

On Wed, 29 Oct 2008 07:15:45 -0400
Jeff Layton <jlayton@...hat.com> wrote:

> My understanding is that there is a push to turn the kernel_thread
> interface into a non-exported symbol and move all kernel threads to use
> the kthread API. This patch changes lockd to use kthread_run to spawn
> the reclaimer thread.
> 
> I've made the assumption here that the extra module references taken
> when we spawn this thread are unnecessary and removed them. I've also
> added a KERN_ERR printk that pops if the thread can't be spawned to warn
> the admin that the locks won't be reclaimed.
> 
> I consider this patch 2.6.29 material.
> 
> Signed-off-by: Jeff Layton <jlayton@...hat.com>
> ---
>  fs/lockd/clntlock.c |   14 +++++++++-----
>  1 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/lockd/clntlock.c b/fs/lockd/clntlock.c
> index 8307dd6..fcc2378 100644
> --- a/fs/lockd/clntlock.c
> +++ b/fs/lockd/clntlock.c
> @@ -14,6 +14,7 @@
>  #include <linux/sunrpc/svc.h>
>  #include <linux/lockd/lockd.h>
>  #include <linux/smp_lock.h>
> +#include <linux/kthread.h>
>  
>  #define NLMDBG_FACILITY		NLMDBG_CLIENT
>  
> @@ -191,11 +192,15 @@ __be32 nlmclnt_grant(const struct sockaddr *addr, const struct nlm_lock *lock)
>  void
>  nlmclnt_recovery(struct nlm_host *host)
>  {
> +	struct task_struct *task;
> +
>  	if (!host->h_reclaiming++) {
>  		nlm_get_host(host);
> -		__module_get(THIS_MODULE);
> -		if (kernel_thread(reclaimer, host, CLONE_FS | CLONE_FILES) < 0)
> -			module_put(THIS_MODULE);
> +		task = kthread_run(reclaimer, host, "%s-reclaim", host->h_name);
> +		if (IS_ERR(task))
> +			printk(KERN_ERR "lockd: unable to spawn reclaimer "
> +				"thread. Locks for %s won't be reclaimed! "
> +				"(%ld)\n", host->h_name, PTR_ERR(task));
>  	}
>  }
>  
> @@ -207,7 +212,6 @@ reclaimer(void *ptr)
>  	struct file_lock *fl, *next;
>  	u32 nsmstate;
>  
> -	daemonize("%s-reclaim", host->h_name);
>  	allow_signal(SIGKILL);
>  
>  	down_write(&host->h_rwsem);
> @@ -261,5 +265,5 @@ restart:
>  	nlm_release_host(host);
>  	lockd_down();
>  	unlock_kernel();
> -	module_put_and_exit(0);
> +	return 0;
>  }

Looks OK to me.  I assume the SIGKILL handling has been carefully tested?


Is it correct to emit a warning and keep going if the thread didn't
start?  Or would it be safer&saner to fail the whole mount (or whatever
syscall we're doing here..)



I see this:

	/* Why are we leaking memory here? --okir */
	if (signalled())
		continue;

is that still true?  It seems unlikely that what appears to be a pretty
gross leak has been around for so long.

This code needs some BKL-removal love.
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