linux-kernel - Re: [RFC][PATCH] fs/partitions/msdos: directly check if FAT boot sector

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Date:	Sat, 01 Mar 2008 10:38:39 +0100
From:	Frank Seidel <fseidel@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: [RFC][PATCH] fs/partitions/msdos: directly check if FAT boot
 sector

Andrew Morton schrieb:
> fs/partitions/msdos.c: In function 'msdos_partition':
> fs/partitions/msdos.c:446: warning: comparison is always true due to limited range of data type
> 
> didn't you get this?

Yes, sorry, but i saw it too late after posting.

> The reason is that FAT_VALID_MEDIA() is bogus:

yes, i stated this in our bug to the complaint
(https://bugzilla.novell.com/show_bug.cgi?id=364365#c15), but should have
also posted it here, sorry.

> #define FAT_VALID_MEDIA(x)      ((0xF8 <= (x) && (x) <= 0xFF) || (x) == 0xF0)
> 
> It appears that the on-disk field which FAT_VALID_MEDIA() is designed to
> test is only 8-bit, so the comparison with 0xff is pointless.  The only
> existing caller of FAT_VALID_MEDIA() cheats by copying the value into a
> local unsigned int first.
> 
> So I'll leave things as they are for now, but I'd ask that someone can
> confirm that we should simply remove the 0xff test from FAT_VALID_MEDIA()?

At least in my opinion it should be removed.

Thanks,
Frank
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