mei: always copy the read buffer if data is ready

Copy completed callback content to the user space
if we have such callback ready in the beginning of the read.
Simplify offset processing logic as byproduct.

This is a refinement for:
commit 139aacf757fc ("mei: fix read after read scenario")

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
index 677d0362f334e842abb2c8c2439260978249b871..36ca15234344aad8b415c1732edd3052000657d6 100644 (file)
--- a/drivers/misc/mei/main.c
+++ b/drivers/misc/mei/main.c
@@ -159,27 +159,22 @@ static ssize_t mei_read(struct file *file, char __user *ubuf,
                goto out;
        }
 
+       if (ubuf == NULL) {
+               rets = -EMSGSIZE;
+               goto out;
+       }
+
        if (cl == &dev->iamthif_cl) {
                rets = mei_amthif_read(dev, file, ubuf, length, offset);
                goto out;
        }
 
        cb = mei_cl_read_cb(cl, file);
-       if (cb) {
-               /* read what left */
-               if (cb->buf_idx > *offset)
-                       goto copy_buffer;
-               /* offset is beyond buf_idx we have no more data return 0 */
-               if (cb->buf_idx > 0 && cb->buf_idx <= *offset) {
-                       rets = 0;
-                       goto free;
-               }
-               /* Offset needs to be cleaned for contiguous reads*/
-               if (cb->buf_idx == 0 && *offset > 0)
-                       *offset = 0;
-       } else if (*offset > 0) {
+       if (cb)
+               goto copy_buffer;
+
+       if (*offset > 0)
                *offset = 0;
-       }
 
        err = mei_cl_read_start(cl, length, file);
        if (err && err != -EBUSY) {
@@ -231,10 +226,10 @@ static ssize_t mei_read(struct file *file, char __user *ubuf,
                goto free;
        }
 
-       cl_dbg(dev, cl, "buf.size = %d buf.idx = %ld\n",
-           cb->buf.size, cb->buf_idx);
-       if (length == 0 || ubuf == NULL || *offset > cb->buf_idx) {
-               rets = -EMSGSIZE;
+       cl_dbg(dev, cl, "buf.size = %d buf.idx = %ld offset = %lld\n",
+              cb->buf.size, cb->buf_idx, *offset);
+       if (*offset >= cb->buf_idx) {
+               rets = 0;
                goto free;
        }
 
@@ -255,6 +250,7 @@ static ssize_t mei_read(struct file *file, char __user *ubuf,
 
 free:
        mei_io_cb_free(cb);
+       *offset = 0;
 
 out:
        cl_dbg(dev, cl, "end mei read rets = %d\n", rets);