proc: unify mem_read() and mem_write()

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.

Cc: stable@kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index c3617ea..be19090 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -718,57 +718,13 @@ static int mem_open(struct inode* inode, struct file* file)
        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;
@@ -779,30 +735,48 @@ static ssize_t mem_write(struct file * file, const char __user *buf,
 
        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) {