linux-kernel - RE: [PATCH v4 0/3] Fix find_first_zero

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Message-ID: <5a6a30994101482c94f16203e3c8ba7d@AcuMS.aculab.com>
Date:   Tue, 12 Dec 2017 14:33:52 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Niklas Cassel' <niklas.cassel@...s.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
CC:     "kishon@...com" <kishon@...com>, Niklas Cassel <niklass@...s.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v4 0/3] Fix find_first_zero_bit() usage

From: Niklas Cassel
> find_first_zero_bit()'s parameter 'size' is defined in bits,
> not in bytes.
> 
> Calling find_first_zero_bit() with the wrong size unit
> will lead to insidious bugs.
> 
> Fix all uses of find_first_zero_bit() called with
> sizeof() as size argument in drivers/pci.
...

Isn't all this code just using the wrong function.
Shouldn't they be using ffz() (or whatever it is called)
to find the first zero in a numeric argument rather that
find_first_zero_bit() which is intended for large bitmaps.

Perhaps the type for 'large bitmaps' should be:
struct {
	unsigned long bitmap_bits[0];
} bitmap;
rather than unsigned long[].

	David