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>

1 files changed, 32 insertions, 58 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index c3617ea7830b..be1909041685 100644
--- 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) {