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Subject[RFC][PATCH] nameing reserved pages [3/3]
showing state of memmap by /dev/memstate.
-- Kame

/dev/memstate shows status of memmap.
A user can read state of a page as a byte.
This feature is useful for Memory-hotplug and other stuffs,
where we have to investigate for what a page is.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>



---

linux-2.6.12-rc2-kamezawa/drivers/char/mem.c | 63 +++++++++++++++++++++++++++
1 files changed, 63 insertions(+)

diff -puN drivers/char/mem.c~show_memstate drivers/char/mem.c
--- linux-2.6.12-rc2/drivers/char/mem.c~show_memstate 2005-04-20 10:39:40.000000000 +0900
+++ linux-2.6.12-rc2-kamezawa/drivers/char/mem.c 2005-04-20 16:51:45.000000000 +0900
@@ -715,6 +715,59 @@ static int open_port(struct inode * inod
return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}

+static inline unsigned char get_page_type(struct page *page)
+{
+ if ( !PageReserved(page) )
+ return Page_Common;
+ return reserved_page_type(page);
+}
+
+static ssize_t read_memstate(struct file *file, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ unsigned long pfn = *ppos;
+ unsigned long left, written;
+ ssize_t ret;
+ int len, i;
+ struct page *page;
+ char *kbuf;
+
+ if (!count)
+ return 0;
+
+ if (!access_ok(VERIFY_WRITE, buf, count))
+ return -EFAULT;
+
+ left = count;
+ written = 0;
+ kbuf = (char *)__get_free_page(GFP_KERNEL);
+
+ if (!kbuf)
+ return -ENOMEM;
+ ret = -EFAULT;
+ /* copy data */
+ while (left) {
+ len = (left < PAGE_SIZE) ? left : PAGE_SIZE;
+ for (i = 0; i < len; i++, pfn++) {
+ if ( !pfn_valid(pfn) ) {
+ kbuf[i] = Page_Invalid;
+ continue;
+ }
+ page = pfn_to_page(pfn);
+ kbuf[i] = get_page_type(page);
+ }
+ if (copy_to_user(buf, kbuf, len))
+ goto err_out;
+ written += len;
+ left -= len;
+ }
+ *ppos = pfn;
+ ret = written;
+ err_out:
+ free_page((unsigned long)kbuf);
+ return ret;
+}
+
#define zero_lseek null_lseek
#define full_lseek null_lseek
#define write_zero write_null
@@ -770,6 +823,11 @@ static struct file_operations full_fops
.write = write_full,
};

+static struct file_operations memstate_fops = {
+ .llseek = memory_lseek,
+ .read = read_memstate,
+};
+
static ssize_t kmsg_write(struct file * file, const char __user * buf,
size_t count, loff_t *ppos)
{
@@ -825,6 +883,9 @@ static int memory_open(struct inode * in
case 11:
filp->f_op = &kmsg_fops;
break;
+ case 12:
+ filp->f_op = &memstate_fops;
+ break;
default:
return -ENXIO;
}
@@ -854,6 +915,7 @@ static const struct {
{8, "random", S_IRUGO | S_IWUSR, &random_fops},
{9, "urandom", S_IRUGO | S_IWUSR, &urandom_fops},
{11,"kmsg", S_IRUGO | S_IWUSR, &kmsg_fops},
+ {12,"memstate", S_IRUSR | S_IRGRP, &memstate_fops},
};

static struct class_simple *mem_class;
@@ -870,6 +932,7 @@ static int __init chr_dev_init(void)
class_simple_device_add(mem_class,
MKDEV(MEM_MAJOR, devlist[i].minor),
NULL, devlist[i].name);
+ printk("creating mem device %d %d\n",i,devlist[i].minor);
devfs_mk_cdev(MKDEV(MEM_MAJOR, devlist[i].minor),
S_IFCHR | devlist[i].mode, devlist[i].name);
}
_
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