afs: Introduce a statistics proc file

Introduce a proc file that displays a bunch of statistics for the AFS
filesystem in the current network namespace.
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/dir.c

@@ -206,6 +206,7 @@ bool afs_dir_check_page(struct inode *dir, struct page *page)
 	}
 
 checked:
+	afs_stat_v(vnode, n_read_dir);
 	SetPageChecked(page);
 	return true;
 
@@ -868,6 +869,7 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
 	    dentry->d_name.name[dentry->d_name.len - 1] == 's')
 		return afs_lookup_atsys(dir, dentry, key);
 
+	afs_stat_v(dvnode, n_lookup);
 	inode = afs_do_lookup(dir, dentry, key);
 	if (IS_ERR(inode)) {
 		ret = PTR_ERR(inode);
@@ -1062,6 +1064,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 		goto out_valid; /* the dir contents are unchanged */
 
 	_debug("dir modified");
+	afs_stat_v(dir, n_reval);
 
 	/* search the directory for this vnode */
 	ret = afs_do_lookup_one(&dir->vfs_inode, dentry, &fid, key);

fs/afs/inode.c

@@ -366,6 +366,9 @@ void afs_zap_data(struct afs_vnode *vnode)
 {
 	_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
 
+	if (S_ISDIR(vnode->vfs_inode.i_mode))
+		afs_stat_v(vnode, n_inval);
+
 #ifdef CONFIG_AFS_FSCACHE
 	fscache_invalidate(vnode->cache);
 #endif

fs/afs/internal.h

@@ -257,9 +257,15 @@ struct afs_net {
 	struct mutex		lock_manager_mutex;
 
 	/* Misc */
-	struct proc_dir_entry	*proc_afs;		/* /proc/net/afs directory */
+	struct proc_dir_entry	*proc_afs;	/* /proc/net/afs directory */
 	struct afs_sysnames	*sysnames;
 	rwlock_t		sysnames_lock;
+
+	/* Statistics counters */
+	atomic_t		n_lookup;	/* Number of lookups done */
+	atomic_t		n_reval;	/* Number of dentries needing revalidation */
+	atomic_t		n_inval;	/* Number of invalidations by the server */
+	atomic_t		n_read_dir;	/* Number of directory pages read */
 };
 
 extern const char afs_init_sysname[];
@@ -777,6 +783,13 @@ static inline void afs_put_net(struct afs_net *net)
 {
 }
 
+static inline void __afs_stat(atomic_t *s)
+{
+	atomic_inc(s);
+}
+
+#define afs_stat_v(vnode, n) __afs_stat(&afs_v2net(vnode)->n)
+
 /*
  * misc.c
  */

fs/afs/proc.c

@@ -152,6 +152,8 @@ static const struct file_operations afs_proc_sysname_fops = {
 	.write		= afs_proc_sysname_write,
 };
 
+static const struct file_operations afs_proc_stats_fops;
+
 /*
  * initialise the /proc/fs/afs/ directory
  */
@@ -166,6 +168,7 @@ int afs_proc_init(struct afs_net *net)
 	if (!proc_create("cells", 0644, net->proc_afs, &afs_proc_cells_fops) ||
 	    !proc_create("rootcell", 0644, net->proc_afs, &afs_proc_rootcell_fops) ||
 	    !proc_create("servers", 0644, net->proc_afs, &afs_proc_servers_fops) ||
+	    !proc_create("stats", 0644, net->proc_afs, &afs_proc_stats_fops) ||
 	    !proc_create("sysname", 0644, net->proc_afs, &afs_proc_sysname_fops))
 		goto error_tree;
 
@@ -897,3 +900,37 @@ static int afs_proc_sysname_show(struct seq_file *m, void *v)
 		seq_printf(m, "%s\n", sysnames->subs[i]);
 	return 0;
 }
+
+/*
+ * Display general per-net namespace statistics
+ */
+static int afs_proc_stats_show(struct seq_file *m, void *v)
+{
+	struct afs_net *net = afs_seq2net(m);
+
+	seq_puts(m, "kAFS statistics\n");
+
+	seq_printf(m, "dir-mgmt: look=%u reval=%u inval=%u\n",
+		   atomic_read(&net->n_lookup),
+		   atomic_read(&net->n_reval),
+		   atomic_read(&net->n_inval));
+
+	seq_printf(m, "dir-data: rdpg=%u\n",
+		   atomic_read(&net->n_read_dir));
+	return 0;
+}
+
+/*
+ * Open "/proc/fs/afs/stats" to allow reading of the stat counters.
+ */
+static int afs_proc_stats_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, afs_proc_stats_show, NULL);
+}
+
+static const struct file_operations afs_proc_stats_fops = {
+	.open		= afs_proc_stats_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release        = single_release,
+};