dma-buf: Add DmaBufTotal counter in meminfo

This adds a total used dma-buf memory. Details
can be found in debugfs, however it is not for everyone
and not always available.

Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>

drivers/dma-buf/dma-buf.c

@@ -37,6 +37,7 @@ struct dma_buf_list {
 };
 
 static struct dma_buf_list db_list;
+static atomic_long_t dma_buf_size;
 
 static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
 {
@@ -79,6 +80,7 @@ static void dma_buf_release(struct dentry *dentry)
 	if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
 		dma_resv_fini(dmabuf->resv);
 
+	atomic_long_sub(dmabuf->size, &dma_buf_size);
 	module_put(dmabuf->owner);
 	kfree(dmabuf->name);
 	kfree(dmabuf);
@@ -586,6 +588,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
 	mutex_lock(&db_list.lock);
 	list_add(&dmabuf->list_node, &db_list.head);
 	mutex_unlock(&db_list.lock);
+	atomic_long_add(dmabuf->size, &dma_buf_size);
 
 	return dmabuf;
 
@@ -1346,6 +1349,15 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
 }
 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
 
+/**
+ * dma_buf_get_size - Return the used nr pages by dma-buf
+ */
+long dma_buf_get_size(void)
+{
+	return atomic_long_read(&dma_buf_size) >> PAGE_SHIFT;
+}
+EXPORT_SYMBOL_GPL(dma_buf_get_size);
+
 #ifdef CONFIG_DEBUG_FS
 static int dma_buf_debug_show(struct seq_file *s, void *unused)
 {

fs/proc/meminfo.c

@@ -16,6 +16,7 @@
 #ifdef CONFIG_CMA
 #include <linux/cma.h>
 #endif
+#include <linux/dma-buf.h>
 #include <asm/page.h>
 #include "internal.h"
 
@@ -145,6 +146,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	show_val_kb(m, "CmaFree:        ",
 		    global_zone_page_state(NR_FREE_CMA_PAGES));
 #endif
+	show_val_kb(m, "DmaBufTotal:    ", dma_buf_get_size());
 
 	hugetlb_report_meminfo(m);
 

include/linux/dma-buf.h

@@ -507,4 +507,5 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
 		 unsigned long);
 int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
 void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
+long dma_buf_get_size(void);
 #endif /* __DMA_BUF_H__ */