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Subject[patch 11/55] proc: unify mem_read() and mem_write()
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------
From: Oleg Nesterov <oleg@redhat.com>

commit 572d34b946bae070debd42db1143034d9687e13f upstream.

No functional changes, cleanup and preparation.

mem_read() and mem_write() are very similar. Move this code into the
new common helper, mem_rw(), which takes the additional "int write"
argument.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/proc/base.c | 90 ++++++++++++++++++++-------------------------------------
1 file changed, 32 insertions(+), 58 deletions(-)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -782,57 +782,13 @@ static int mem_open(struct inode* inode,
return 0;
}

-static ssize_t mem_read(struct file * file, char __user * buf,
- size_t count, loff_t *ppos)
+static ssize_t mem_rw(struct file *file, char __user *buf,
+ size_t count, loff_t *ppos, int write)
{
- int ret;
- char *page;
- unsigned long src = *ppos;
struct mm_struct *mm = file->private_data;
-
- if (!mm)
- return 0;
-
- page = (char *)__get_free_page(GFP_TEMPORARY);
- if (!page)
- return -ENOMEM;
-
- ret = 0;
-
- while (count > 0) {
- int this_len, retval;
-
- this_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
- retval = access_remote_vm(mm, src, page, this_len, 0);
- if (!retval) {
- if (!ret)
- ret = -EIO;
- break;
- }
-
- if (copy_to_user(buf, page, retval)) {
- ret = -EFAULT;
- break;
- }
-
- ret += retval;
- src += retval;
- buf += retval;
- count -= retval;
- }
- *ppos = src;
-
- free_page((unsigned long) page);
- return ret;
-}
-
-static ssize_t mem_write(struct file * file, const char __user *buf,
- size_t count, loff_t *ppos)
-{
- int copied;
+ unsigned long addr = *ppos;
+ ssize_t copied;
char *page;
- unsigned long dst = *ppos;
- struct mm_struct *mm = file->private_data;

if (!mm)
return 0;
@@ -843,30 +799,48 @@ static ssize_t mem_write(struct file * f

copied = 0;
while (count > 0) {
- int this_len, retval;
+ int this_len = min_t(int, count, PAGE_SIZE);

- this_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
- if (copy_from_user(page, buf, this_len)) {
+ if (write && copy_from_user(page, buf, this_len)) {
copied = -EFAULT;
break;
}
- retval = access_remote_vm(mm, dst, page, this_len, 1);
- if (!retval) {
+
+ this_len = access_remote_vm(mm, addr, page, this_len, write);
+ if (!this_len) {
if (!copied)
copied = -EIO;
break;
}
- copied += retval;
- buf += retval;
- dst += retval;
- count -= retval;
+
+ if (!write && copy_to_user(buf, page, this_len)) {
+ copied = -EFAULT;
+ break;
+ }
+
+ buf += this_len;
+ addr += this_len;
+ copied += this_len;
+ count -= this_len;
}
- *ppos = dst;
+ *ppos = addr;

free_page((unsigned long) page);
return copied;
}

+static ssize_t mem_read(struct file *file, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ return mem_rw(file, buf, count, ppos, 0);
+}
+
+static ssize_t mem_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ return mem_rw(file, (char __user*)buf, count, ppos, 1);
+}
+
loff_t mem_lseek(struct file *file, loff_t offset, int orig)
{
switch (orig) {



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