mm: cma: make writeable CMA debugfs optional

Make writeable CMA debugfs optional. This will allow exposing readonly CMA
debugfs entries for stats.

Change-Id: I35cbaa11df5a1d8bb4a2496fcc1b6166ce64abf0
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>

mm/Kconfig

@@ -529,6 +529,15 @@ config CMA_DEBUGFS
 	help
 	  Turns on the DebugFS interface for CMA.
 
+config  CMA_ALLOW_WRITE_DEBUGFS
+	depends on CMA_DEBUGFS
+	bool "Allow CMA debugfs write"
+	help
+	  Say 'y' here to allow the CMA debugfs write.
+	  CMA debugfs write could be risky as it allows
+	  cma allocation, so it is not recommended to
+	  enable this option on any production device.
+
 config CMA_AREAS
 	int "Maximum count of the CMA areas"
 	depends on CMA

mm/cma_debug.c

@@ -76,6 +76,7 @@ static int cma_maxchunk_get(void *data, u64 *val)
 }
 DEFINE_SIMPLE_ATTRIBUTE(cma_maxchunk_fops, cma_maxchunk_get, NULL, "%llu\n");
 
+#ifdef CONFIG_CMA_ALLOW_WRITE_DEBUGFS
 static void cma_add_to_cma_mem_list(struct cma *cma, struct cma_mem *mem)
 {
 	spin_lock(&cma->mem_head_lock);
@@ -134,8 +135,13 @@ static int cma_free_write(void *data, u64 val)
 
 	return cma_free_mem(cma, pages);
 }
+#else
+#define cma_free_write NULL
+#endif
+
 DEFINE_SIMPLE_ATTRIBUTE(cma_free_fops, NULL, cma_free_write, "%llu\n");
 
+#ifdef CONFIG_CMA_ALLOW_WRITE_DEBUGFS
 static int cma_alloc_mem(struct cma *cma, int count)
 {
 	struct cma_mem *mem;
@@ -166,6 +172,10 @@ static int cma_alloc_write(void *data, u64 val)
 
 	return cma_alloc_mem(cma, pages);
 }
+#else
+#define cma_alloc_write NULL
+#endif
+
 DEFINE_SIMPLE_ATTRIBUTE(cma_alloc_fops, NULL, cma_alloc_write, "%llu\n");
 
 static void cma_debugfs_add_one(struct cma *cma, int idx)