Add callbacks for displaying KSTAT_TYPE_RAW kstats

The current implementation for displaying kstats of type KSTAT_TYPE_RAW
is rather crude. This patch attempts to enhance this handling by
allowing a kstat user to register formatting callbacks which can
optionally be used.

The callbacks allow the user to implement functions for interpreting
their data and transposing it into a character buffer. This buffer,
containing a string representation of the raw data, is then be displayed
through the current /proc textual interface.

Additionally the kstats are made writable because it's now possible
to provide a useful handler via the existing ks_update() interface.

Signed-off-by: Prakash Surya <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Issue #296

1 files changed, 105 insertions, 14 deletions

diff --git a/module/spl/spl-kstat.c b/module/spl/spl-kstat.c
index 4e900c066..57aabe2d0 100644
--- a/module/spl/spl-kstat.c
+++ b/module/spl/spl-kstat.c
@@ -41,10 +41,25 @@ static kmutex_t kstat_module_lock;
 static struct list_head kstat_module_list;
 static kid_t kstat_id;
 
-static void
+static int
+kstat_resize_raw(kstat_t *ksp)
+{
+	if (ksp->ks_raw_bufsize == KSTAT_RAW_MAX)
+		return ENOMEM;
+
+	vmem_free(ksp->ks_raw_buf, ksp->ks_raw_bufsize);
+	ksp->ks_raw_bufsize = MIN(ksp->ks_raw_bufsize * 2, KSTAT_RAW_MAX);
+	ksp->ks_raw_buf = vmem_alloc(ksp->ks_raw_bufsize, KM_SLEEP);
+
+	return 0;
+}
+
+static int
 kstat_seq_show_headers(struct seq_file *f)
 {
         kstat_t *ksp = (kstat_t *)f->private;
+	int rc = 0;
+
         ASSERT(ksp->ks_magic == KS_MAGIC);
 
         seq_printf(f, "%d %d 0x%02x %d %d %lld %lld\n",
@@ -54,7 +69,17 @@ kstat_seq_show_headers(struct seq_file *f)
 
 	switch (ksp->ks_type) {
                 case KSTAT_TYPE_RAW:
-                        seq_printf(f, "raw data");
+restart:
+                        if (ksp->ks_raw_ops.headers) {
+                                rc = ksp->ks_raw_ops.headers(
+                                    ksp->ks_raw_buf, ksp->ks_raw_bufsize);
+				if (rc == ENOMEM && !kstat_resize_raw(ksp))
+					goto restart;
+				if (!rc)
+	                                seq_puts(f, ksp->ks_raw_buf);
+                        } else {
+                                seq_printf(f, "raw data\n");
+                        }
                         break;
                 case KSTAT_TYPE_NAMED:
                         seq_printf(f, "%-31s %-4s %s\n",
@@ -92,6 +117,8 @@ kstat_seq_show_headers(struct seq_file *f)
                 default:
                         PANIC("Undefined kstat type %d\n", ksp->ks_type);
         }
+
+	return -rc;
 }
 
 static int
@@ -232,9 +259,19 @@ kstat_seq_show(struct seq_file *f, void *p)
 
 	switch (ksp->ks_type) {
                 case KSTAT_TYPE_RAW:
-                        ASSERT(ksp->ks_ndata == 1);
-                        rc = kstat_seq_show_raw(f, ksp->ks_data,
-                                                ksp->ks_data_size);
+restart:
+                        if (ksp->ks_raw_ops.data) {
+                                rc = ksp->ks_raw_ops.data(
+				    ksp->ks_raw_buf, ksp->ks_raw_bufsize, p);
+				if (rc == ENOMEM && !kstat_resize_raw(ksp))
+					goto restart;
+				if (!rc)
+	                                seq_puts(f, ksp->ks_raw_buf);
+                        } else {
+                                ASSERT(ksp->ks_ndata == 1);
+                                rc = kstat_seq_show_raw(f, ksp->ks_data,
+                                                        ksp->ks_data_size);
+                        }
                         break;
                 case KSTAT_TYPE_NAMED:
                         rc = kstat_seq_show_named(f, (kstat_named_t *)p);
@@ -255,13 +292,17 @@ kstat_seq_show(struct seq_file *f, void *p)
                         PANIC("Undefined kstat type %d\n", ksp->ks_type);
         }
 
-        return rc;
+        return -rc;
 }
 
 int
 kstat_default_update(kstat_t *ksp, int rw)
 {
 	ASSERT(ksp != NULL);
+
+	if (rw == KSTAT_WRITE)
+		return (EACCES);
+
 	return 0;
 }
 
@@ -273,7 +314,10 @@ kstat_seq_data_addr(kstat_t *ksp, loff_t n)
 
 	switch (ksp->ks_type) {
                 case KSTAT_TYPE_RAW:
-	                rc = ksp->ks_data;
+                        if (ksp->ks_raw_ops.addr)
+                                rc = ksp->ks_raw_ops.addr(ksp, n);
+                        else
+                                rc = ksp->ks_data;
                         break;
                 case KSTAT_TYPE_NAMED:
                         rc = ksp->ks_data + n * sizeof(kstat_named_t);
@@ -307,13 +351,18 @@ kstat_seq_start(struct seq_file *f, loff_t *pos)
 
         mutex_enter(&ksp->ks_lock);
 
+        if (ksp->ks_type == KSTAT_TYPE_RAW) {
+                ksp->ks_raw_bufsize = PAGE_SIZE;
+                ksp->ks_raw_buf = vmem_alloc(ksp->ks_raw_bufsize, KM_SLEEP);
+        }
+
         /* Dynamically update kstat, on error existing kstats are used */
         (void) ksp->ks_update(ksp, KSTAT_READ);
 
 	ksp->ks_snaptime = gethrtime();
 
-        if (!n)
-                kstat_seq_show_headers(f);
+        if (!n && kstat_seq_show_headers(f))
+		SRETURN(NULL);
 
         if (n >= ksp->ks_ndata)
                 SRETURN(NULL);
@@ -341,6 +390,9 @@ kstat_seq_stop(struct seq_file *f, void *v)
         kstat_t *ksp = (kstat_t *)f->private;
         ASSERT(ksp->ks_magic == KS_MAGIC);
 
+	if (ksp->ks_type == KSTAT_TYPE_RAW)
+		vmem_free(ksp->ks_raw_buf, ksp->ks_raw_bufsize);
+
         mutex_exit(&ksp->ks_lock);
 }
 
@@ -408,13 +460,47 @@ proc_kstat_open(struct inode *inode, struct file *filp)
         return rc;
 }
 
+static ssize_t
+proc_kstat_write(struct file *filp, const char __user *buf,
+		 size_t len, loff_t *ppos)
+{
+	struct seq_file *f = filp->private_data;
+	kstat_t *ksp = f->private;
+	int rc;
+
+	ASSERT(ksp->ks_magic == KS_MAGIC);
+
+	mutex_enter(ksp->ks_lock);
+	rc = ksp->ks_update(ksp, KSTAT_WRITE);
+	mutex_exit(ksp->ks_lock);
+
+	if (rc)
+		return (-rc);
+
+	*ppos += len;
+	return (len);
+}
+
 static struct file_operations proc_kstat_operations = {
-        .open           = proc_kstat_open,
-        .read           = seq_read,
-        .llseek         = seq_lseek,
-        .release        = seq_release,
+	.open		= proc_kstat_open,
+	.write		= proc_kstat_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
 };
 
+void
+__kstat_set_raw_ops(kstat_t *ksp,
+		    int (*headers)(char *buf, size_t size),
+		    int (*data)(char *buf, size_t size, void *data),
+		    void *(*addr)(kstat_t *ksp, loff_t index))
+{
+	ksp->ks_raw_ops.headers = headers;
+	ksp->ks_raw_ops.data    = data;
+	ksp->ks_raw_ops.addr    = addr;
+}
+EXPORT_SYMBOL(__kstat_set_raw_ops);
+
 kstat_t *
 __kstat_create(const char *ks_module, int ks_instance, const char *ks_name,
              const char *ks_class, uchar_t ks_type, uint_t ks_ndata,
@@ -453,6 +539,11 @@ __kstat_create(const char *ks_module, int ks_instance, const char *ks_name,
 	ksp->ks_flags = ks_flags;
 	ksp->ks_update = kstat_default_update;
 	ksp->ks_private = NULL;
+	ksp->ks_raw_ops.headers = NULL;
+	ksp->ks_raw_ops.data = NULL;
+	ksp->ks_raw_ops.addr = NULL;
+	ksp->ks_raw_buf = NULL;
+	ksp->ks_raw_bufsize = 0;
 
 	switch (ksp->ks_type) {
                 case KSTAT_TYPE_RAW:
@@ -526,7 +617,7 @@ __kstat_install(kstat_t *ksp)
 
 	mutex_enter(&ksp->ks_lock);
 	ksp->ks_owner = module;
-	ksp->ks_proc = proc_create_data(ksp->ks_name, 0444,
+	ksp->ks_proc = proc_create_data(ksp->ks_name, 0644,
 	    module->ksm_proc, &proc_kstat_operations, (void *)ksp);
 	if (ksp->ks_proc == NULL) {
 		list_del_init(&ksp->ks_list);