[patch 10/10] nfsd: fix hung up of nfs client while sync write data to nfs server

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Wei Yongjun <yjwei@xxxxxxxxxxxxxx>

commit a0d24b295aed7a9daf4ca36bd4784e4d40f82303 upstream.

nfsd: fix hung up of nfs client while sync write data to nfs server

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.

This patch fixed the problem.

Signed-off-by: Wei Yongjun <yjwei@xxxxxxxxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
Cc: Chuck Ebbert <cebbert@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/nfsd/vfs.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1003,6 +1003,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, s
 	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);
 	}
@@ -1048,10 +1049,9 @@ nfsd_vfs_write(struct svc_rqst *rqstp, s
 	}
 
 	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;


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