linux-kernel - Re: [PATCH][next] scsi: scsi_debug: remove a redundant assignment to variable ret

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Message-ID: <191de70f-b019-4329-8e93-ea142aefdc7a@stanley.mountain>
Date: Wed, 2 Oct 2024 18:19:45 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Colin Ian King <colin.i.king@...il.com>
Cc: "James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
	"Martin K . Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] scsi: scsi_debug: remove a redundant assignment to
 variable ret

Generally, functions which report the number of bytes copied are an anti-pattern.

	bytes = copied();
	if (bytes < 0)
		return bytes;  <-- forgot to handle partial copies

	bytes = copied();
	if (bytes < 0 || bytes != total)
		return bytes;  <-- forgot the error code for partial copies

	bytes = copied();
	if (bytes < sizeof())  <-- negative error codes type promoted to positive
		return -EIO;

We've seen subsystems move away from this.  Other subsystems are like "Ugh.
Updating all the callers is a headache.  Let's either report that everything
copied or a negative error code, but not the partial bytes."  Now the first
two examples above magically work.

regards,
dan carpenter