Subject: Re: p = kmalloc(sizeof(*p), )
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: Linux Kernel List <linux-kernel@vger.kernel.org>,
       Linus Torvalds <torvalds@osdl.org>, Al Viro <viro@ftp.linux.org.uk>
In-Reply-To: <20050918100627.GA16007@flint.arm.linux.org.uk>
References: <20050918100627.GA16007@flint.arm.linux.org.uk>
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Date: Sun, 18 Sep 2005 12:04:34 +0100
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On Sul, 2005-09-18 at 11:06 +0100, Russell King wrote:
> I completely disagree with the above assertion for the following
> reasons:

Ditto, but you forgot #4. People are always getting sizeof(*p) wrong, in
particular forgetting that p happens to be a void *, or a struct that is
some generic type not the full space for the more complex object
allocated, so using (*p) everywhere just causes more memory scribbles.

If it bugs people add a kmalloc_object macro that is

#define new_object(foo, gfp) (foo *)kmalloc(sizeof(foo), (gfp))

then you can

	x = new_object(struct frob, GFP_KERNEL)

Other good practice in many cases is a single routine which allocates
and initialises the structure and is used by all allocators of that
object. That removes duplicate initialisers, stops people forgetting to
update all cases, allows better debug and far more.
 
Alan

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