Re: block ioctl to read/write last sector

From: Michael E Brown (michael_e_brown@dell.com)
Date: Wed Feb 14 2001 - 10:56:43 EST

On Wed, 14 Feb 2001 Andries.Brouwer@cwi.nl wrote:

>
> So if you add a 1-block partition that contains the last
> sector of the disk, all should be fine.
>

Oh! I didn't get your meaning before. I think I understand now. The
problem with this is that the tests for block writeability are not done on
a per-partition basis. They are done on a whole block device basis. see
fs/block_dev.c in block_read() and block_write(). The following test kills
us:

        if (blk_size[MAJOR(dev)])
                size = ((loff_t) blk_size[MAJOR(dev)][MINOR(dev)] <<
BLOCK_SIZE_BITS) >> blocksize_bits;
        else
                size = INT_MAX;
        while (count>0) {
                if (block >= size)
                        return written ? written : -ENOSPC; 

--
Michael Brown
Linux Systems Group
Dell Computer Corp

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This archive was generated by hypermail 2b29 : Thu Feb 15 2001 - 21:00:24 EST