mm: cma: allocation trigger

Provides a userspace interface to trigger a CMA allocation.

Usage:

        echo [pages] > alloc

This would provide testing/fuzzing access to the CMA allocation paths.
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/cma.c

@@ -123,6 +123,12 @@ static int __init cma_activate_area(struct cma *cma)
 	} while (--i);
 
 	mutex_init(&cma->lock);
+
+#ifdef CONFIG_CMA_DEBUGFS
+	INIT_HLIST_HEAD(&cma->mem_head);
+	spin_lock_init(&cma->mem_head_lock);
+#endif
+
 	return 0;
 
 err:

mm/cma.h

@@ -7,6 +7,10 @@ struct cma {
 	unsigned long   *bitmap;
 	unsigned int order_per_bit; /* Order of pages represented by one bit */
 	struct mutex    lock;
+#ifdef CONFIG_CMA_DEBUGFS
+	struct hlist_head mem_head;
+	spinlock_t mem_head_lock;
+#endif
 };
 
 extern struct cma cma_areas[MAX_CMA_AREAS];

mm/cma_debug.c

@@ -7,9 +7,18 @@
 
 #include <linux/debugfs.h>
 #include <linux/cma.h>
+#include <linux/list.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
 
 #include "cma.h"
 
+struct cma_mem {
+	struct hlist_node node;
+	struct page *p;
+	unsigned long n;
+};
+
 static struct dentry *cma_debugfs_root;
 
 static int cma_debugfs_get(void *data, u64 *val)
@@ -23,6 +32,46 @@ static int cma_debugfs_get(void *data, u64 *val)
 
 DEFINE_SIMPLE_ATTRIBUTE(cma_debugfs_fops, cma_debugfs_get, NULL, "%llu\n");
 
+static void cma_add_to_cma_mem_list(struct cma *cma, struct cma_mem *mem)
+{
+	spin_lock(&cma->mem_head_lock);
+	hlist_add_head(&mem->node, &cma->mem_head);
+	spin_unlock(&cma->mem_head_lock);
+}
+
+static int cma_alloc_mem(struct cma *cma, int count)
+{
+	struct cma_mem *mem;
+	struct page *p;
+
+	mem = kzalloc(sizeof(*mem), GFP_KERNEL);
+	if (!mem)
+		return -ENOMEM;
+
+	p = cma_alloc(cma, count, CONFIG_CMA_ALIGNMENT);
+	if (!p) {
+		kfree(mem);
+		return -ENOMEM;
+	}
+
+	mem->p = p;
+	mem->n = count;
+
+	cma_add_to_cma_mem_list(cma, mem);
+
+	return 0;
+}
+
+static int cma_alloc_write(void *data, u64 val)
+{
+	int pages = val;
+	struct cma *cma = data;
+
+	return cma_alloc_mem(cma, pages);
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(cma_alloc_fops, NULL, cma_alloc_write, "%llu\n");
+
 static void cma_debugfs_add_one(struct cma *cma, int idx)
 {
 	struct dentry *tmp;
@@ -33,6 +82,9 @@ static void cma_debugfs_add_one(struct cma *cma, int idx)
 
 	tmp = debugfs_create_dir(name, cma_debugfs_root);
 
+	debugfs_create_file("alloc", S_IWUSR, cma_debugfs_root, cma,
+				&cma_alloc_fops);
+
 	debugfs_create_file("base_pfn", S_IRUGO, tmp,
 				&cma->base_pfn, &cma_debugfs_fops);
 	debugfs_create_file("count", S_IRUGO, tmp,