nfsd: use DEFINE_SHOW_ATTRIBUTE to define nfsd_reply_cache_stats_fops

Use DEFINE_SHOW_ATTRIBUTE helper macro to simplify the code.

nfsd_net is converted from seq_file->file instead of seq_file->private in
nfsd_reply_cache_stats_show().

Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
[ cel: reduce line length ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: ChenXiaoSong

fs/nfsd/cache.h

@@ -84,6 +84,6 @@ int	nfsd_reply_cache_init(struct nfsd_net *);
 void	nfsd_reply_cache_shutdown(struct nfsd_net *);
 int	nfsd_cache_lookup(struct svc_rqst *);
 void	nfsd_cache_update(struct svc_rqst *, int, __be32 *);
-int	nfsd_reply_cache_stats_open(struct inode *, struct file *);
+int	nfsd_reply_cache_stats_show(struct seq_file *m, void *v);
 
 #endif /* NFSCACHE_H */

fs/nfsd/nfscache.c

@@ -604,9 +604,10 @@ nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
  * scraping this file for info should test the labels to ensure they're
  * getting the correct field.
  */
-static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
+int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
 {
-	struct nfsd_net *nn = m->private;
+	struct nfsd_net *nn = net_generic(file_inode(m->file)->i_sb->s_fs_info,
+					  nfsd_net_id);
 
 	seq_printf(m, "max entries:           %u\n", nn->max_drc_entries);
 	seq_printf(m, "num entries:           %u\n",
@@ -626,11 +627,3 @@ static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
 	seq_printf(m, "cachesize at longest:  %u\n", nn->longest_chain_cachesize);
 	return 0;
 }
-
-int nfsd_reply_cache_stats_open(struct inode *inode, struct file *file)
-{
-	struct nfsd_net *nn = net_generic(file_inode(file)->i_sb->s_fs_info,
-								nfsd_net_id);
-
-	return single_open(file, nfsd_reply_cache_stats_show, nn);
-}

fs/nfsd/nfsctl.c

@@ -204,12 +204,7 @@ static const struct file_operations pool_stats_operations = {
 	.release	= nfsd_pool_stats_release,
 };
 
-static const struct file_operations reply_cache_stats_operations = {
-	.open		= nfsd_reply_cache_stats_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
+DEFINE_SHOW_ATTRIBUTE(nfsd_reply_cache_stats);
 
 static const struct file_operations filecache_ops = {
 	.open		= nfsd_file_cache_stats_open,
@@ -1354,7 +1349,8 @@ static int nfsd_fill_super(struct super_block *sb, struct fs_context *fc)
 		[NFSD_Threads] = {"threads", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Pool_Threads] = {"pool_threads", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Pool_Stats] = {"pool_stats", &pool_stats_operations, S_IRUGO},
-		[NFSD_Reply_Cache_Stats] = {"reply_cache_stats", &reply_cache_stats_operations, S_IRUGO},
+		[NFSD_Reply_Cache_Stats] = {"reply_cache_stats",
+					&nfsd_reply_cache_stats_fops, S_IRUGO},
 		[NFSD_Versions] = {"versions", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Ports] = {"portlist", &transaction_ops, S_IWUSR|S_IRUGO},
 		[NFSD_MaxBlkSize] = {"max_block_size", &transaction_ops, S_IWUSR|S_IRUGO},