6 files changed, 185 insertions, 47 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,
diff --git a/arch/um/include/mem_user.h b/arch/um/include/mem_user.h
index a1064c5823bf..a54514d2cc3a 100644
--- a/arch/um/include/mem_user.h
+++ b/arch/um/include/mem_user.h
@@ -49,7 +49,6 @@ extern int iomem_size;
 extern unsigned long host_task_size;
 extern unsigned long task_size;
 
-extern void check_devanon(void);
 extern int init_mem_user(void);
 extern void setup_memory(void *entry);
 extern unsigned long find_iomem(char *driver, unsigned long *len_out);
diff --git a/arch/um/include/os.h b/arch/um/include/os.h
index d3d1bc6074ef..5fb84e889b2b 100644
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -205,6 +205,8 @@ extern int os_map_memory(void *virt, int fd, unsigned long long off,
 extern int os_protect_memory(void *addr, unsigned long len, 
                              int r, int w, int x);
 extern int os_unmap_memory(void *addr, int len);
+extern int os_drop_memory(void *addr, int length);
+extern int can_drop_memory(void);
 extern void os_flush_stdout(void);
 
 /* tt.c
diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index 9d7d69a523bb..6ab372da9657 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -121,36 +121,11 @@ int create_tmp_file(unsigned long long len)
         return(fd);
 }
 
-static int create_anon_file(unsigned long long len)
-{
-        void *addr;
-        int fd;
-
-        fd = open("/dev/anon", O_RDWR);
-        if(fd < 0) {
-                perror("opening /dev/anon");
-                exit(1);
-        }
-
-        addr = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-        if(addr == MAP_FAILED){
-                perror("mapping physmem file");
-                exit(1);
-        }
-        munmap(addr, len);
-
-        return(fd);
-}
-
-extern int have_devanon;
-
 int create_mem_file(unsigned long long len)
 {
         int err, fd;
 
-        if(have_devanon)
-                fd = create_anon_file(len);
-        else fd = create_tmp_file(len);
+        fd = create_tmp_file(len);
 
         err = os_set_exec_close(fd, 1);
         if(err < 0){
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index d261888f39c4..8176b0b52047 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -11,6 +11,7 @@
 #include <linux/unistd.h>
 #include <sys/mman.h>
 #include <sys/wait.h>
+#include <sys/mman.h>
 #include "ptrace_user.h"
 #include "os.h"
 #include "user.h"
@@ -20,6 +21,7 @@
 #include "kern_util.h"
 #include "longjmp.h"
 #include "skas_ptrace.h"
+#include "kern_constants.h"
 
 #define ARBITRARY_ADDR -1
 #define FAILURE_PID    -1
@@ -187,6 +189,48 @@ int os_unmap_memory(void *addr, int len)
         return(0);
 }
 
+#ifndef MADV_REMOVE
+#define MADV_REMOVE     0x5             /* remove these pages & resources */
+#endif
+
+int os_drop_memory(void *addr, int length)
+{
+        int err;
+
+        err = madvise(addr, length, MADV_REMOVE);
+        if(err < 0)
+                err = -errno;
+        return err;
+}
+
+int can_drop_memory(void)
+{
+        void *addr;
+        int fd;
+
+        printk("Checking host MADV_REMOVE support...");
+        fd = create_mem_file(UM_KERN_PAGE_SIZE);
+        if(fd < 0){
+                printk("Creating test memory file failed, err = %d\n", -fd);
+                return 0;
+        }
+
+        addr = mmap64(NULL, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
+                      MAP_PRIVATE, fd, 0);
+        if(addr == MAP_FAILED){
+                printk("Mapping test memory file failed, err = %d\n", -errno);
+                return 0;
+        }
+
+        if(madvise(addr, UM_KERN_PAGE_SIZE, MADV_REMOVE) != 0){
+                printk("MADV_REMOVE failed, err = %d\n", -errno);
+                return 0;
+        }
+
+        printk("OK\n");
+        return 1;
+}
+
 void init_new_thread_stack(void *sig_stack, void (*usr1_handler)(int))
 {
         int flags = 0, pages;
diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c
index 32753131f8d8..387e26af301a 100644
--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -470,25 +470,6 @@ int can_do_skas(void)
 }
 #endif
 
-int have_devanon = 0;
-
-/* Runs on boot kernel stack - already safe to use printk. */
-
-void check_devanon(void)
-{
-        int fd;
-
-        printk("Checking for /dev/anon on the host...");
-        fd = open("/dev/anon", O_RDWR);
-        if(fd < 0){
-                printk("Not available (open failed with errno %d)\n", errno);
-                return;
-        }
-
-        printk("OK\n");
-        have_devanon = 1;
-}
-
 int __init parse_iomem(char *str, int *add)
 {
         struct iomem_region *new;
@@ -664,6 +645,5 @@ void os_check_bugs(void)
 {
         check_ptrace();
         check_sigio();
-        check_devanon();
 }