Re: [PATCH] pipefs unique inode numbers

[Jeff Layton <jlayton@redhat.com>]

Bodo Eggert wrote:
> change pipefs to use a unique inode number equal to the memory
> address unless it would be truncated.
>
> Signed-Off-By: Bodo Eggert <7eggert@gmx.de>
> ---
> Tested on i386.
>
> --- 2.6.19/fs/pipe.c.ori	2007-01-30 22:02:46.000000000 +0100
> +++ 2.6.19/fs/pipe.c	2007-01-30 23:22:27.000000000 +0100
> @@ -864,6 +864,10 @@ static struct inode * get_pipe_inode(voi
>  	inode->i_uid = current->fsuid;
>  	inode->i_gid = current->fsgid;
>  	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
> +	/* The address of *inode is unique, so we'll get an unique inode number.
> +	 * Off cause this will not work for 32 bit inodes on 64 bit systems. */
> +	if (sizeof(inode->i_ino) >= sizeof(struct inode*))
> +		inode->i_ino = (unsigned int) inode;
>
>  	return inode;
>

Also, that patch would break many 32-bit programs not compiled with large
offsets when run in compatibility mode on a 64-bit kernel. If they were to
do a stat on this inode, it would likely generate an EOVERFLOW error since
the pointer address would probably not fit in a 32 bit field.

That problem was the whole impetus for this set of patches.

-- Jeff
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