1 files changed, 13 insertions, 43 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 917403fe10da..524b707894ef 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -622,53 +622,23 @@ static ssize_t splice_write_null(struct pipe_inode_info *pipe, struct file *out,
         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_null);
 }
 
-static ssize_t read_zero(struct file *file, char __user *buf,
-                         size_t count, loff_t *ppos)
+static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
 {
-        size_t written;
-
-        if (!count)
-                return 0;
-
-        if (!access_ok(VERIFY_WRITE, buf, count))
-                return -EFAULT;
-
-        written = 0;
-        while (count) {
-                unsigned long unwritten;
-                size_t chunk = count;
+        size_t written = 0;
 
+        while (iov_iter_count(iter)) {
+                size_t chunk = iov_iter_count(iter), n;
                 if (chunk > PAGE_SIZE)
                         chunk = PAGE_SIZE;      /* Just for latency reasons */
-                unwritten = __clear_user(buf, chunk);
-                written += chunk - unwritten;
-                if (unwritten)
-                        break;
+                n = iov_iter_zero(chunk, iter);
+                if (!n && iov_iter_count(iter))
+                        return written ? written : -EFAULT;
+                written += n;
                 if (signal_pending(current))
                         return written ? written : -ERESTARTSYS;
-                buf += chunk;
-                count -= chunk;
                 cond_resched();
         }
-        return written ? written : -EFAULT;
-}
-
-static ssize_t aio_read_zero(struct kiocb *iocb, const struct iovec *iov,
-                             unsigned long nr_segs, loff_t pos)
-{
-        size_t written = 0;
-        unsigned long i;
-        ssize_t ret;
-
-        for (i = 0; i < nr_segs; i++) {
-                ret = read_zero(iocb->ki_filp, iov[i].iov_base, iov[i].iov_len,
-                                &pos);
-                if (ret < 0)
-                        break;
-                written += ret;
-        }
-
-        return written ? written : -EFAULT;
+        return written;
 }
 
 static int mmap_zero(struct file *file, struct vm_area_struct *vma)
@@ -738,7 +708,6 @@ static int open_port(struct inode *inode, struct file *filp)
 #define zero_lseek      null_lseek
 #define full_lseek      null_lseek
 #define write_zero      write_null
-#define read_full       read_zero
 #define aio_write_zero  aio_write_null
 #define open_mem        open_port
 #define open_kmem       open_mem
@@ -783,9 +752,9 @@ static const struct file_operations port_fops = {
 
 static const struct file_operations zero_fops = {
         .llseek         = zero_lseek,
-        .read           = read_zero,
+        .read           = new_sync_read,
         .write          = write_zero,
-        .aio_read       = aio_read_zero,
+        .read_iter      = read_iter_zero,
         .aio_write      = aio_write_zero,
         .mmap           = mmap_zero,
 };
@@ -802,7 +771,8 @@ static struct backing_dev_info zero_bdi = {
 
 static const struct file_operations full_fops = {
         .llseek         = full_lseek,
-        .read           = read_full,
+        .read           = new_sync_read,
+        .read_iter      = read_iter_zero,
         .write          = write_full,
 };