linux-kernel - did vfs_read or something related to it get broken?

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Message-ID: <CAGRSmLu0gE9PS61Nm_ay6Cd3WK_=jhbCov7gb1jPL7-MZhaVzQ@mail.gmail.com>
Date:   Fri, 30 Jun 2017 16:10:56 -0700
From:   "David F." <df7729@...il.com>
To:     linux-kernel <linux-kernel@...r.kernel.org>
Subject: did vfs_read or something related to it get broken?

Hi,

I have a driver that reads data from a file that has worked from
kernel 3.x up to 4.9.13.  I haven't tried all the other 4.9's or 4.10,
or 4.11.6 or earlier, but in 4.11.7 it's now broken and an error is
returned.   It's based on
http://krishnamohanlinux.blogspot.com/2013/12/how-to-write-to-file-from-kernel-module.html

Is there a new requirement of some sort or did it get broken?

int driver_file_read(struct file *file, unsigned char *data, unsigned int size)
{
  int ret;
  mm_segment_t oldfs;

  // get file pointer
  loff_t pos = file->f_pos;

  oldfs   = get_fs();
  set_fs(get_ds());

  ret=vfs_read(file, data, size, &pos);

  set_fs(oldfs);

  // update file pointer
  file->f_pos=pos;

   return (ret);
}

struct file *driver_file_open(const char *path, int flags, int mode, int *err)
{
  int ec=0;
  struct file *filp = NULL;
  filp=filp_open(path, flags, mode);
  if (IS_ERR(filp)) {
    ec=PTR_ERR(filp);
    filp=NULL;
  }
  // update callers error code
  if (err) {
    *err=ec;
  }
  // return pointer to file
  return (filp);
}