linux-kernel - RE: [PATCH RFC V2] staging: kpc2000: use int for wait_for_completion

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Message-ID: <SN6PR02MB4016A8EC6E8402A26BDE54CDEE390@SN6PR02MB4016.namprd02.prod.outlook.com>
Date:   Mon, 29 Apr 2019 15:02:10 +0000
From:   Matt Sickler <Matt.Sickler@...tronics.com>
To:     Nicholas Mc Guire <hofrat@...dl.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH RFC V2] staging: kpc2000: use int for
 wait_for_completion_interruptible

ACK.   However, that part isn't the only part of that function that uses "return rv" though.
There's another part that does "rv = get_user_pages(...)" and get_user_pages() returns a long.
Does this same kind of change need to happen for that case?

>-----Original Message-----
>From: Nicholas Mc Guire <hofrat@...dl.org>
>Sent: Saturday, April 27, 2019 4:15 AM
>To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>Cc: Matt Sickler <Matt.Sickler@...tronics.com>; devel@...verdev.osuosl.org;
>linux-kernel@...r.kernel.org; Nicholas Mc Guire <hofrat@...dl.org>
>Subject: [PATCH RFC V2] staging: kpc2000: use int for
>wait_for_completion_interruptible
>
>
>weit_for_completion_interruptible returns in (0 on completion and -
>ERESTARTSYS on interruption) - so use an int not long for API conformance
>and simplify the logic here a bit: need not check explicitly for == 0 as this is
>either -ERESTARTSYS or 0.
>
>Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
>---
>
>Problem located with experimental API conformance checking cocci script
>
>V2: kbuild reported a missing closing comment - seems that I managed
>    send out the the initial version before compile testing/checkpatching
>    sorry for the noise.
>
>Not sure if making such point-wise fixes makes much sense - this driver has a
>number of issues both style-wise and API compliance wise.
>
>Note that kpc_dma_transfer() returns int not long - currently rv (long) is being
>returned in most places (some places do return int) - so the return handling
>here is a bit inconsistent.
>
>Patch was compile-tested with: x86_64_defconfig + KPC2000=y,
>KPC2000_DMA=y (with a number of unrelated sparse warnings about non-
>declared symbols, and  smatch warnings about overflowing constants as well
>as coccicheck warning  about usless casting)
>
>Patch is against 5.1-rc6 (localversion-next is next-20190426)
>
> drivers/staging/kpc2000/kpc_dma/fileops.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
>diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c
>b/drivers/staging/kpc2000/kpc_dma/fileops.c
>index 5741d2b..66f0d5a 100644
>--- a/drivers/staging/kpc2000/kpc_dma/fileops.c
>+++ b/drivers/staging/kpc2000/kpc_dma/fileops.c
>@@ -38,6 +38,7 @@ int  kpc_dma_transfer(struct dev_private_data *priv,
>struct kiocb *kcb, unsigned  {
>        unsigned int i = 0;
>        long rv = 0;
>+       int ret = 0;
>        struct kpc_dma_device *ldev;
>        struct aio_cb_data *acd;
>        DECLARE_COMPLETION_ONSTACK(done); @@ -180,16 +181,17 @@ int
>kpc_dma_transfer(struct dev_private_data *priv, struct kiocb *kcb, unsigned
>
>        // If this is a synchronous kiocb, we need to put the calling process to
>sleep until the transfer is complete
>        if (kcb == NULL || is_sync_kiocb(kcb)){
>-               rv = wait_for_completion_interruptible(&done);
>-               // If the user aborted (rv == -ERESTARTSYS), we're no longer
>responsible for cleaning up the acd
>-               if (rv == -ERESTARTSYS){
>+               ret = wait_for_completion_interruptible(&done);
>+               /* If the user aborted (ret == -ERESTARTSYS), we're
>+                * no longer responsible for cleaning up the acd
>+                */
>+               if (ret) {
>                        acd->cpl = NULL;
>-               }
>-               if (rv == 0){
>-                       rv = acd->len;
>+               } else {
>+                       ret = acd->len;
>                        kfree(acd);
>                }
>-               return rv;
>+               return ret;
>        }
>
>        return -EIOCBQUEUED;
>--
>2.1.4