linux-kernel - Re: [patch V3 01/10] cleanup: Provide retain

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Message-ID: <4a6efcf37b3cf8812dcfaaa66d4c1760b3e2a95a.camel@HansenPartnership.com>
Date: Mon, 17 Mar 2025 09:57:29 -0400
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
Cc: Marc Zyngier <maz@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
 Jonathan Cameron <Jonathan.Cameron@...wei.com>, Nishanth Menon <nm@...com>,
 Dhruva Gole <d-gole@...com>, Tero Kristo <kristo@...nel.org>, Santosh
 Shilimkar <ssantosh@...nel.org>, Logan Gunthorpe <logang@...tatee.com>,
 Dave Jiang <dave.jiang@...el.com>, Jon Mason <jdmason@...zu.us>, Allen
 Hubbe <allenbh@...il.com>, ntb@...ts.linux.dev,  Bjorn Helgaas
 <bhelgaas@...gle.com>, linux-pci@...r.kernel.org, Michael Kelley
 <mhklinux@...look.com>, Wei Liu <wei.liu@...nel.org>, Haiyang Zhang
 <haiyangz@...rosoft.com>,  linux-hyperv@...r.kernel.org, Wei Huang
 <wei.huang2@....com>, Manivannan Sadhasivam
 <manivannan.sadhasivam@...aro.org>, "Martin K. Petersen"
 <martin.petersen@...cle.com>,  linux-scsi@...r.kernel.org, Jonathan Cameron
 <Jonathan.Cameron@...ei.com>
Subject: Re: [patch V3 01/10] cleanup: Provide retain_ptr()

On Mon, 2025-03-17 at 14:29 +0100, Thomas Gleixner wrote:
[...]
> +/*
> + * Only for situations where an allocation is handed in to another
> function
> + * and consumed by that function on success.
> + *
> + *	struct foo *f __free(kfree) = kzalloc(sizeof(*f),
> GFP_KERNEL);
> + *
> + *	setup(f);
> + *	if (some_condition)
> + *		return -EINVAL;
> + *	....
> + *	ret = bar(f);
> + *	if (!ret)
> + *		retain_ptr(f);
> + *	return ret;
> + */
> +#define retain_ptr(p)				\
> +	__get_and_null(p, NULL)

This doesn't score very highly on the Rusty API design scale because it
can be used anywhere return_ptr() should be used.  To force the
distinction between the two cases at the compiler level, should there
be a cast to void in the above to prevent using the return value?

Regards,

James