linux-kernel - Re: [PATCH] Illustration of warning explosion silliness

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Message-Id: <20060927183507.5ef244f3.akpm@osdl.org>
Date:	Wed, 27 Sep 2006 18:35:07 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	linux-scsi@...r.kernel.org, Greg KH <greg@...ah.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Illustration of warning explosion silliness

On Wed, 27 Sep 2006 20:58:30 -0400
Jeff Garzik <jeff@...zik.org> wrote:

> The following patch (DO NOT APPLY) illustrates why
> device_for_each_child() should not be marked with __must_check.
> 
> The function returns the return value of the actor function, and ceases
> iteration upon error.
> 
> However, _every_ case in drivers/scsi has a hardcoded return value,
> illustrating how it is quite valid to not check the return value of this
> function.
> 

What does "has a hardcoded return value" mean?

AFICT the problem here is that (for example) (going up the call stack in
the callee->caller direction):

scsi_internal_device_block() returns an error code

but device_block() drops that on the floor

so target_block() drops it on the floor too

so scsi_target_block() drops it on the floor too

It's a small matter of (correct kernel) programming to correctly propagate
the scsi_internal_device_block() error code all the way back out of
scsi_target_block().

It all looks rather sloppy?
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