1 files changed, 138 insertions, 0 deletions

diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 1488816588ea..d060fce4940e 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -20,6 +20,8 @@
 #include "linux/namei.h"
 #include "linux/proc_fs.h"
 #include "linux/syscalls.h"
+#include "linux/list.h"
+#include "linux/mm.h"
 #include "linux/console.h"
 #include "asm/irq.h"
 #include "asm/uaccess.h"
@@ -347,6 +349,142 @@ static struct mc_device *mconsole_find_dev(char *name)
         return(NULL);
 }
 
+#define UNPLUGGED_PER_PAGE \
+        ((PAGE_SIZE - sizeof(struct list_head)) / sizeof(unsigned long))
+
+struct unplugged_pages {
+        struct list_head list;
+        void *pages[UNPLUGGED_PER_PAGE];
+};
+
+static unsigned long long unplugged_pages_count = 0;
+static struct list_head unplugged_pages = LIST_HEAD_INIT(unplugged_pages);
+static int unplug_index = UNPLUGGED_PER_PAGE;
+
+static int mem_config(char *str)
+{
+        unsigned long long diff;
+        int err = -EINVAL, i, add;
+        char *ret;
+
+        if(str[0] != '=')
+                goto out;
+
+        str++;
+        if(str[0] == '-')
+                add = 0;
+        else if(str[0] == '+'){
+                add = 1;
+        }
+        else goto out;
+
+        str++;
+        diff = memparse(str, &ret);
+        if(*ret != '\0')
+                goto out;
+
+        diff /= PAGE_SIZE;
+
+        for(i = 0; i < diff; i++){
+                struct unplugged_pages *unplugged;
+                void *addr;
+
+                if(add){
+                        if(list_empty(&unplugged_pages))
+                                break;
+
+                        unplugged = list_entry(unplugged_pages.next,
+                                               struct unplugged_pages, list);
+                        if(unplug_index > 0)
+                                addr = unplugged->pages[--unplug_index];
+                        else {
+                                list_del(&unplugged->list);
+                                addr = unplugged;
+                                unplug_index = UNPLUGGED_PER_PAGE;
+                        }
+
+                        free_page((unsigned long) addr);
+                        unplugged_pages_count--;
+                }
+                else {
+                        struct page *page;
+
+                        page = alloc_page(GFP_ATOMIC);
+                        if(page == NULL)
+                                break;
+
+                        unplugged = page_address(page);
+                        if(unplug_index == UNPLUGGED_PER_PAGE){
+                                INIT_LIST_HEAD(&unplugged->list);
+                                list_add(&unplugged->list, &unplugged_pages);
+                                unplug_index = 0;
+                        }
+                        else {
+                                struct list_head *entry = unplugged_pages.next;
+                                addr = unplugged;
+
+                                unplugged = list_entry(entry,
+                                                       struct unplugged_pages,
+                                                       list);
+                                unplugged->pages[unplug_index++] = addr;
+                                err = os_drop_memory(addr, PAGE_SIZE);
+                                if(err)
+                                        printk("Failed to release memory - "
+                                               "errno = %d\n", err);
+                        }
+
+                        unplugged_pages_count++;
+                }
+        }
+
+        err = 0;
+out:
+        return err;
+}
+
+static int mem_get_config(char *name, char *str, int size, char **error_out)
+{
+        char buf[sizeof("18446744073709551615")];
+        int len = 0;
+
+        sprintf(buf, "%ld", uml_physmem);
+        CONFIG_CHUNK(str, size, len, buf, 1);
+
+        return len;
+}
+
+static int mem_id(char **str, int *start_out, int *end_out)
+{
+        *start_out = 0;
+        *end_out = 0;
+
+        return 0;
+}
+
+static int mem_remove(int n)
+{
+        return -EBUSY;
+}
+
+static struct mc_device mem_mc = {
+        .name           = "mem",
+        .config         = mem_config,
+        .get_config     = mem_get_config,
+        .id             = mem_id,
+        .remove         = mem_remove,
+};
+
+static int mem_mc_init(void)
+{
+        if(can_drop_memory())
+                mconsole_register_dev(&mem_mc);
+        else printk("Can't release memory to the host - memory hotplug won't "
+                    "be supported\n");
+        return 0;
+}
+
+__initcall(mem_mc_init);
+
 #define CONFIG_BUF_SIZE 64
 
 static void mconsole_get_config(int (*get_config)(char *, char *, int,