> On 18 Feb 2019, at 01:32, Ian Lepore <i...@freebsd.org> wrote:
>
> Author: ian
> Date: Sun Feb 17 23:32:09 2019
> New Revision: 344238
> URL: https://svnweb.freebsd.org/changeset/base/344238
>
> Log:
> Restore loader(8)'s ability for lsdev to show partitions within a bsd slice.
>
> I'm pretty sure this used to work at one time, perhaps long ago. It has
> been failing recently because if you call disk_open() with dev->d_partition
> set to -1 when d_slice refers to a bsd slice, it assumes you want it to
> open the first partition within that slice. When you then pass that open
> dev instance to ptable_open(), it tries to read the start of the 'a'
> partition and decides there is no recognizable partition type there.
>
> This restores the old functionality by resetting d_offset to the start
> of the raw slice after disk_open() returns. For good measure, d_partition
> is also set back to -1, although that doesn't currently affect anything.
>
> I would have preferred to make disk_open() avoid such rude assumptions and
> if you ask for partition -1 you get the raw slice. But the commit history
> shows that someone already did that once (r239058), and had to revert it
> (r239232), so I didn't even try to go down that road.
What was the reason for the revert? I still do think the current disk_open()
approach is not good because it does break the promise to get MBR partition
(see common/disk.h).
Of course I can see the appeal for something like “boot disk0:” but case like
that should be solved by iterating partition table, and not by making API to do
wrong thing - if I did ask to for disk0s0: I really would expect to get
disk0s0: and not disk0s0a:
But anyhow, it would be good to understand the actual reasoning behind that
decision.
rgds,
toomas
>
> Modified:
> head/stand/common/disk.c
>
> Modified: head/stand/common/disk.c
> ==============================================================================
> --- head/stand/common/disk.c Sun Feb 17 20:25:07 2019 (r344237)
> +++ head/stand/common/disk.c Sun Feb 17 23:32:09 2019 (r344238)
> @@ -133,6 +133,13 @@ ptable_print(void *arg, const char *pname, const struc
> dev.d_partition = -1;
> if (disk_open(&dev, part->end - part->start + 1,
> od->sectorsize) == 0) {
> + /*
> + * disk_open() for partition -1 on a bsd slice assumes
> + * you want the first bsd partition. Reset things so
> + * that we're looking at the start of the raw slice.
> + */
> + dev.d_partition = -1;
> + dev.d_offset = part->start;
> table = ptable_open(&dev, part->end - part->start + 1,
> od->sectorsize, ptblread);
> if (table != NULL) {
>
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