linux-kernel - Re: [PATCH 2/7] fat: Fix VFAT_IOCTL_READDIR

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Message-ID: <20080701112248.GA17558@cs181140183.pp.htv.fi>
Date:	Tue, 1 Jul 2008 14:22:48 +0300
From:	Adrian Bunk <bunk@...nel.org>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] fat: Fix VFAT_IOCTL_READDIR_xxx and cleanup for
	userland

On Tue, Jul 01, 2008 at 03:40:33AM -0400, Christoph Hellwig wrote:
> On Tue, Jul 01, 2008 at 11:57:03AM +0900, OGAWA Hirofumi wrote:
> > 
> > "struct dirent" is a kernel type here, but is a **different type** in 
> > userspace!  This means both the structure and the IOCTL number is wrong!
> > 
> > So, this adds new "struct __fat_dirent" to generate correct IOCTL
> > number.  And kernel stuff moves to under __KERNEL__.
> 
> Given that the current version can't actually work without defininig
> it's own dirent and thus ioctl number symbolic name I wonder if these
> ioctls are used at all?  They must have been completely untested for
> a while, and I suspect we'd be better off just removing them.

I had the same thought, but when checking this I noticed that at least 
wine works around this problem:

<--  snip  -->

/* just in case... */
#undef VFAT_IOCTL_READDIR_BOTH
#undef USE_GETDENTS

#ifdef linux

/* We want the real kernel dirent structure, not the libc one */
typedef struct
{
    long d_ino;
    long d_off;
    unsigned short d_reclen;
    char d_name[256];
} KERNEL_DIRENT;

/* Define the VFAT ioctl to get both short and long file names */
#define VFAT_IOCTL_READDIR_BOTH  _IOR('r', 1, KERNEL_DIRENT [2] )

<--  snip  -->


cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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