Re: [PATCH] nfsd: fix hung up of nfs client while sync write data to nfs server

["J. Bruce Fields" <bfields@fieldses.org>]

On Tue, May 19, 2009 at 12:03:15PM +0800, Wei Yongjun wrote:
> Commit 'Short write in nfsd becomes a full write to the client'
> (31dec2538e45e9fff2007ea1f4c6bae9f78db724) broken the sync write.
> With the following commands to reproduce:
> 
>   $ mount -t nfs -o sync 192.168.0.21:/nfsroot /mnt
>   $ cd /mnt
>   $ echo aaaa > temp.txt
> 
> Then nfs client is hung up.
> 
> In SYNC mode the server alaways return the write count 0 to the
> client. This is because the value of host_err in nfsd_vfs_write()
> will be overwrite in SYNC mode by 'host_err=nfsd_sync(file);',
> and then we return host_err(which is now 0) as write count.

Undoubtedly correct--applied, thanks!

(But it bugs me that I can't reproduce this: I see the client (mounting
with -osync, as above) send an unstable write followed by an immediate
commit, instead of a stable write.  This is with 2.6.29.30-rc7 on client
and server.)

--b.

> 
> This patch fixed the problem.
> 
> Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
> ---
>  fs/nfsd/vfs.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 6c68ffd..b660435 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1015,6 +1015,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
>  	host_err = vfs_writev(file, (struct iovec __user *)vec, vlen, &offset);
>  	set_fs(oldfs);
>  	if (host_err >= 0) {
> +		*cnt = host_err;
>  		nfsdstats.io_write += host_err;
>  		fsnotify_modify(file->f_path.dentry);
>  	}
> @@ -1060,10 +1061,9 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
>  	}
>  
>  	dprintk("nfsd: write complete host_err=%d\n", host_err);
> -	if (host_err >= 0) {
> +	if (host_err >= 0)
>  		err = 0;
> -		*cnt = host_err;
> -	} else
> +	else
>  		err = nfserrno(host_err);
>  out:
>  	return err;
> -- 
> 1.5.3.8
> 
> 
>