ashmem: switch to ->read_iter

And use the proper VFS helper for using the backing file.

Also make sure we hold ashmem_lock while updating f_pos to make sure that
it's not racy.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 8 insertions, 21 deletions

diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
index 6ba270e0494d..0f695df14c9d 100644
--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -294,19 +294,9 @@ static int ashmem_release(struct inode *ignored, struct file *file)
         return 0;
 }
 
-/**
- * ashmem_read() - Reads a set of bytes from an Ashmem-enabled file
- * @file:          The associated backing file.
- * @buf:           The buffer of data being written to
- * @len:           The number of bytes being read
- * @pos:           The position of the first byte to read.
- *
- * Return: 0 if successful, or another return code if not.
- */
-static ssize_t ashmem_read(struct file *file, char __user *buf,
-                           size_t len, loff_t *pos)
+static ssize_t ashmem_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
-        struct ashmem_area *asma = file->private_data;
+        struct ashmem_area *asma = iocb->ki_filp->private_data;
         int ret = 0;
 
         mutex_lock(&ashmem_mutex);
@@ -320,20 +310,17 @@ static ssize_t ashmem_read(struct file *file, char __user *buf,
                 goto out_unlock;
         }
 
-        mutex_unlock(&ashmem_mutex);
-
         /*
          * asma and asma->file are used outside the lock here.  We assume
          * once asma->file is set it will never be changed, and will not
          * be destroyed until all references to the file are dropped and
          * ashmem_release is called.
          */
-        ret = __vfs_read(asma->file, buf, len, pos);
-        if (ret >= 0)
-                /** Update backing file pos, since f_ops->read() doesn't */
-                asma->file->f_pos = *pos;
-        return ret;
-
+        mutex_unlock(&ashmem_mutex);
+        ret = vfs_iter_read(asma->file, iter, &iocb->ki_pos, 0);
+        mutex_lock(&ashmem_mutex);
+        if (ret > 0)
+                asma->file->f_pos = iocb->ki_pos;
 out_unlock:
         mutex_unlock(&ashmem_mutex);
         return ret;
@@ -834,7 +821,7 @@ static const struct file_operations ashmem_fops = {
         .owner = THIS_MODULE,
         .open = ashmem_open,
         .release = ashmem_release,
-        .read = ashmem_read,
+        .read_iter = ashmem_read_iter,
         .llseek = ashmem_llseek,
         .mmap = ashmem_mmap,
         .unlocked_ioctl = ashmem_ioctl,