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

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

------------------
From: Wei Yongjun <yjwei@cn.fujitsu.com>
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@cn.fujitsu.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
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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