Re: [PATCH v4 10/10] mtd: powernv_flash: Use opal_async_wait_response_interruptible()

[Boris Brezillon]

On Tue, 10 Oct 2017 14:33:02 +1100
Cyril Bur  wrote:

> The OPAL calls performed in this driver shouldn't be using
> opal_async_wait_response() as this performs a wait_event() which, on
> long running OPAL calls could result in hung task warnings. wait_event()
> prevents timely signal delivery which is also undesirable.
> 
> This patch also attempts to quieten down the use of dev_err() when
> errors haven't actually occurred and also to return better information up
> the stack rather than always -EIO.
> 
> Signed-off-by: Cyril Bur 

Have some minor comments (see below). Once addressed you can add

Acked-by: Boris Brezillon 

> ---
>  drivers/mtd/devices/powernv_flash.c | 57 
> +++--
>  1 file changed, 35 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/mtd/devices/powernv_flash.c 
> b/drivers/mtd/devices/powernv_flash.c
> index 3343d4f5c4f3..42383dbca5a6 100644
> --- a/drivers/mtd/devices/powernv_flash.c
> +++ b/drivers/mtd/devices/powernv_flash.c
> @@ -1,7 +1,7 @@
>  /*
>   * OPAL PNOR flash MTD abstraction
>   *
> - * Copyright IBM 2015
> + * Copyright IBM 2015-2017

Not a big deal, but this copyright update is not really related to the
change you describe in your commit message. Maybe this should be done
in a separate commit.

>   *
>   * This program is free software; you can redistribute it and/or modify
>   * it under the terms of the GNU General Public License as published by
> @@ -89,33 +89,46 @@ static int powernv_flash_async_op(struct mtd_info *mtd, 
> enum flash_op op,
>   return -EIO;
>   }
>  
> - if (rc == OPAL_SUCCESS)
> - goto out_success;
> + if (rc == OPAL_ASYNC_COMPLETION) {
> + rc = opal_async_wait_response_interruptible(token, );
> + if (rc) {
> + /*
> +  * If we return the mtd core will free the
> +  * buffer we've just passed to OPAL but OPAL
> +  * will continue to read or write from that
> +  * memory.
> +  * It may be tempting to ultimately return 0
> +  * if we're doing a read or a write since we
> +  * are going to end up waiting until OPAL is
> +  * done. However, because the MTD core sends
> +  * us the userspace request in chunks, we need
> +  * to it know we've been interrupted.

   ^ 'it to' ?

> +  */
> + rc = -EINTR;
> + if (opal_async_wait_response(token, ))
> + dev_err(dev, "opal_async_wait_response() 
> failed\n");
> + goto out;
> + }
> + rc = opal_get_async_rc(msg);
> + }
>  
> - if (rc != OPAL_ASYNC_COMPLETION) {
> + /*
> +  * OPAL does mutual exclusion on the flash, it will return
> +  * OPAL_BUSY.
> +  * During firmware updates by the service processor OPAL may
> +  * be (temporarily) prevented from accessing the flash, in
> +  * this case OPAL will also return OPAL_BUSY.
> +  * Both cases aren't errors exactly but the flash could have
> +  * changed, userspace should be informed.
> +  */
> + if (rc != OPAL_SUCCESS && rc != OPAL_BUSY)
>   dev_err(dev, "opal_flash_async_op(op=%d) failed (rc %d)\n",
>   op, rc);
> - rc = -EIO;
> - goto out;
> - }
>  
> - rc = opal_async_wait_response(token, );
> - if (rc) {
> - dev_err(dev, "opal async wait failed (rc %d)\n", rc);
> - rc = -EIO;
> - goto out;
> - }
> -
> - rc = opal_get_async_rc(msg);
> -out_success:
> - if (rc == OPAL_SUCCESS) {
> - rc = 0;
> - if (retlen)
> + if (rc == OPAL_SUCCESS && retlen)
>   *retlen = len;

There's one too many tabs here.

> - } else {
> - rc = -EIO;
> - }
>  
> + rc = opal_error_code(rc);
>  out:
>   opal_async_release_token(token);
>   return rc;

[PATCH v4 10/10] mtd: powernv_flash: Use opal_async_wait_response_interruptible()

[Cyril Bur]

The OPAL calls performed in this driver shouldn't be using
opal_async_wait_response() as this performs a wait_event() which, on
long running OPAL calls could result in hung task warnings. wait_event()
prevents timely signal delivery which is also undesirable.

This patch also attempts to quieten down the use of dev_err() when
errors haven't actually occurred and also to return better information up
the stack rather than always -EIO.

Signed-off-by: Cyril Bur 
---
 drivers/mtd/devices/powernv_flash.c | 57 +++--
 1 file changed, 35 insertions(+), 22 deletions(-)

diff --git a/drivers/mtd/devices/powernv_flash.c 
b/drivers/mtd/devices/powernv_flash.c
index 3343d4f5c4f3..42383dbca5a6 100644
--- a/drivers/mtd/devices/powernv_flash.c
+++ b/drivers/mtd/devices/powernv_flash.c
@@ -1,7 +1,7 @@
 /*
  * OPAL PNOR flash MTD abstraction
  *
- * Copyright IBM 2015
+ * Copyright IBM 2015-2017
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -89,33 +89,46 @@ static int powernv_flash_async_op(struct mtd_info *mtd, 
enum flash_op op,
return -EIO;
}
 
-   if (rc == OPAL_SUCCESS)
-   goto out_success;
+   if (rc == OPAL_ASYNC_COMPLETION) {
+   rc = opal_async_wait_response_interruptible(token, );
+   if (rc) {
+   /*
+* If we return the mtd core will free the
+* buffer we've just passed to OPAL but OPAL
+* will continue to read or write from that
+* memory.
+* It may be tempting to ultimately return 0
+* if we're doing a read or a write since we
+* are going to end up waiting until OPAL is
+* done. However, because the MTD core sends
+* us the userspace request in chunks, we need
+* to it know we've been interrupted.
+*/
+   rc = -EINTR;
+   if (opal_async_wait_response(token, ))
+   dev_err(dev, "opal_async_wait_response() 
failed\n");
+   goto out;
+   }
+   rc = opal_get_async_rc(msg);
+   }
 
-   if (rc != OPAL_ASYNC_COMPLETION) {
+   /*
+* OPAL does mutual exclusion on the flash, it will return
+* OPAL_BUSY.
+* During firmware updates by the service processor OPAL may
+* be (temporarily) prevented from accessing the flash, in
+* this case OPAL will also return OPAL_BUSY.
+* Both cases aren't errors exactly but the flash could have
+* changed, userspace should be informed.
+*/
+   if (rc != OPAL_SUCCESS && rc != OPAL_BUSY)
dev_err(dev, "opal_flash_async_op(op=%d) failed (rc %d)\n",
op, rc);
-   rc = -EIO;
-   goto out;
-   }
 
-   rc = opal_async_wait_response(token, );
-   if (rc) {
-   dev_err(dev, "opal async wait failed (rc %d)\n", rc);
-   rc = -EIO;
-   goto out;
-   }
-
-   rc = opal_get_async_rc(msg);
-out_success:
-   if (rc == OPAL_SUCCESS) {
-   rc = 0;
-   if (retlen)
+   if (rc == OPAL_SUCCESS && retlen)
*retlen = len;
-   } else {
-   rc = -EIO;
-   }
 
+   rc = opal_error_code(rc);
 out:
opal_async_release_token(token);
return rc;
-- 
2.14.2