linux-kernel - Re: [PATCH] nfs-util: Add cache_flush in mountd UMNT procedure.

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Date:	Tue, 10 Jul 2012 10:59:37 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	SteveD@...hat.com, Trond.Myklebust@...app.com,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	Vivek Trivedi <vtrivedi018@...il.com>
Subject: Re: [PATCH] nfs-util: Add cache_flush in mountd UMNT procedure.

On Sat, Jul 07, 2012 at 11:17:39PM -0400, Namjae Jeon wrote:
> For removing storage device - user needs to safely un-mount the device
> and then eject. But if 'EBUSY' occurs in umount then it will create
> confusion for the user as it will mean some I/O is in progress - and
> won't allow user to safely ejecting device.

The one drawback is that recovering from the cache flushes might be a
little expensive if you have a lot of exports in use.

I'm curious, since you said this was for a usb disk: are users expected
to just unplug it (in which case--is it read only?) or do they have some
way of unmounting before they pull the plug?

--b.

> 
> 1. Without this patch:
> 
> On NFS Client:
> $ mount.nfs <NFS_SERVER>:/mnt /mnt
> $ umount.nfs /mnt
> 
> On NFS Server:
> $ umount /mnt
> umount: can't umount /mnt: Device or resource busy
> 
> 2. With this patch:
> 
> On NFS Client:
> $ mount.nfs <NFS_SERVER>:/mnt /mnt
> $ umount.nfs /mnt
> 
> On NFS Server:
> $ umount.nfs /mnt --> umount successful
> 
> Signed-off-by: Namjae Jeon <linkinjeon@...il.com>
> Signed-off-by: Vivek Trivedi <vtrivedi018@...il.com>
> ---
>  utils/mountd/mountd.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/utils/mountd/mountd.c b/utils/mountd/mountd.c
> index bcf5080..2b190fb 100644
> --- a/utils/mountd/mountd.c
> +++ b/utils/mountd/mountd.c
> @@ -275,6 +275,7 @@ mount_umnt_1_svc(struct svc_req *rqstp, dirpath *argp, void *UNUSED(resp))
>  		return 1;
>  
>  	mountlist_del(host_ntop(sap, buf, sizeof(buf)), p);
> +	cache_flush(1);
>  	return 1;
>  }
>  
> @@ -292,6 +293,7 @@ mount_umntall_1_svc(struct svc_req *rqstp, void *UNUSED(argp),
>  	auth_reload();
>  
>  	mountlist_del_all(nfs_getrpccaller(rqstp->rq_xprt));
> +	cache_flush(1);
>  	return 1;
>  }
>  
> -- 
> 1.7.9.5
> 
--
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