nfsd: use DEFINE_SHOW_ATTRIBUTE to define nfsd_file_cache_stats_fops

Use DEFINE_SHOW_ATTRIBUTE helper macro to simplify the code.
Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/filecache.c

@@ -1212,7 +1212,7 @@ nfsd_file_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
  * scraping this file for info should test the labels to ensure they're
  * getting the correct field.
  */
-static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
+int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
 {
 	unsigned long releases = 0, pages_flushed = 0, evictions = 0;
 	unsigned long hits = 0, acquisitions = 0;
@@ -1259,8 +1259,3 @@ static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
 	seq_printf(m, "pages flushed: %lu\n", pages_flushed);
 	return 0;
 }
-
-int nfsd_file_cache_stats_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, nfsd_file_cache_stats_show, NULL);
-}

fs/nfsd/filecache.h

@@ -60,5 +60,5 @@ __be32 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		  unsigned int may_flags, struct nfsd_file **nfp);
 __be32 nfsd_file_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		  unsigned int may_flags, struct nfsd_file **nfp);
-int	nfsd_file_cache_stats_open(struct inode *, struct file *);
+int nfsd_file_cache_stats_show(struct seq_file *m, void *v);
 #endif /* _FS_NFSD_FILECACHE_H */

fs/nfsd/nfsctl.c

@@ -206,12 +206,7 @@ static const struct file_operations pool_stats_operations = {
 
 DEFINE_SHOW_ATTRIBUTE(nfsd_reply_cache_stats);
 
-static const struct file_operations filecache_ops = {
-	.open		= nfsd_file_cache_stats_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
+DEFINE_SHOW_ATTRIBUTE(nfsd_file_cache_stats);
 
 /*----------------------------------------------------------------------------*/
 /*
@@ -1355,7 +1350,7 @@ static int nfsd_fill_super(struct super_block *sb, struct fs_context *fc)
 		[NFSD_Ports] = {"portlist", &transaction_ops, S_IWUSR|S_IRUGO},
 		[NFSD_MaxBlkSize] = {"max_block_size", &transaction_ops, S_IWUSR|S_IRUGO},
 		[NFSD_MaxConnections] = {"max_connections", &transaction_ops, S_IWUSR|S_IRUGO},
-		[NFSD_Filecache] = {"filecache", &filecache_ops, S_IRUGO},
+		[NFSD_Filecache] = {"filecache", &nfsd_file_cache_stats_fops, S_IRUGO},
 #if defined(CONFIG_SUNRPC_GSS) || defined(CONFIG_SUNRPC_GSS_MODULE)
 		[NFSD_SupportedEnctypes] = {"supported_krb5_enctypes",
 					&supported_enctypes_fops, S_IRUGO},