mm: cma: release trigger

Provides a userspace interface to trigger a CMA release.

Usage:

        echo [pages] > free

This would provide testing/fuzzing access to the CMA release paths.

[akpm@linux-foundation.org: coding-style fixes]
[mhocko@suse.cz: fix build]
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: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 58 insertions, 0 deletions

diff --git a/mm/cma_debug.c b/mm/cma_debug.c
index f3baa413ab33..ae41faeed596 100644
--- a/mm/cma_debug.c
+++ b/mm/cma_debug.c
@@ -10,6 +10,7 @@
 #include <linux/list.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
+#include <linux/mm_types.h>
 
 #include "cma.h"
 
@@ -39,6 +40,60 @@ static void cma_add_to_cma_mem_list(struct cma *cma, struct cma_mem *mem)
         spin_unlock(&cma->mem_head_lock);
 }
 
+static struct cma_mem *cma_get_entry_from_list(struct cma *cma)
+{
+        struct cma_mem *mem = NULL;
+
+        spin_lock(&cma->mem_head_lock);
+        if (!hlist_empty(&cma->mem_head)) {
+                mem = hlist_entry(cma->mem_head.first, struct cma_mem, node);
+                hlist_del_init(&mem->node);
+        }
+        spin_unlock(&cma->mem_head_lock);
+
+        return mem;
+}
+
+static int cma_free_mem(struct cma *cma, int count)
+{
+        struct cma_mem *mem = NULL;
+
+        while (count) {
+                mem = cma_get_entry_from_list(cma);
+                if (mem == NULL)
+                        return 0;
+
+                if (mem->n <= count) {
+                        cma_release(cma, mem->p, mem->n);
+                        count -= mem->n;
+                        kfree(mem);
+                } else if (cma->order_per_bit == 0) {
+                        cma_release(cma, mem->p, count);
+                        mem->p += count;
+                        mem->n -= count;
+                        count = 0;
+                        cma_add_to_cma_mem_list(cma, mem);
+                } else {
+                        pr_debug("cma: cannot release partial block when order_per_bit != 0\n");
+                        cma_add_to_cma_mem_list(cma, mem);
+                        break;
+                }
+        }
+
+        return 0;
+
+}
+
+static int cma_free_write(void *data, u64 val)
+{
+        int pages = val;
+        struct cma *cma = data;
+
+        return cma_free_mem(cma, pages);
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(cma_free_fops, NULL, cma_free_write, "%llu\n");
+
 static int cma_alloc_mem(struct cma *cma, int count)
 {
         struct cma_mem *mem;
@@ -85,6 +140,9 @@ static void cma_debugfs_add_one(struct cma *cma, int idx)
         debugfs_create_file("alloc", S_IWUSR, cma_debugfs_root, cma,
                                 &cma_alloc_fops);
 
+        debugfs_create_file("free", S_IWUSR, cma_debugfs_root, cma,
+                                &cma_free_fops);
+
         debugfs_create_file("base_pfn", S_IRUGO, tmp,
                                 &cma->base_pfn, &cma_debugfs_fops);
         debugfs_create_file("count", S_IRUGO, tmp,