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SubjectRe: /dev/loop0 over lvm... leading to d-state :-(

Jens,

thanks for the b_dev hint you provided.

On Thu, Apr 05, 2001 at 04:49:42PM +0200, Jens Axboe wrote:
> On Thu, Apr 05 2001, Jens Axboe wrote:
> > To the LVM folks: you can't use b_dev or b_blocknr inside your
> > make_request_fn, it destroys stacking drivers such as loop. And
> > is just plain wrong in the general case too.
>
> Irks, another one. lvm_make_request_fn also needs to call b_end_io
> if a map fails.

This is wrong.

In case of an io error we do already call buffer_IO_error() on 2.4 in lvm_map().

In 2.2 ll_rw_block() does change the state of the buffer and calls
b_end_io() for us at the end of the function:

sorry:
for (i = 0; i < nr; i++) {
if (bh[i]) {
clear_bit(BH_Dirty, &bh[i]->b_state);
clear_bit(BH_Uptodate, &bh[i]->b_state);
bh[i]->b_end_io(bh[i], 0);
}
}

> Updated patch attached, I'll collate further
> patches if I find more :-)

Please do that. Thanks again.

Regards,
Heinz -- The LVM Guy --

>
>
> --
> Jens Axboe
>

> --- /opt/kernel/linux-2.4.3/drivers/md/lvm.c Mon Jan 29 01:11:20 2001
> +++ drivers/md/lvm.c Thu Apr 5 16:48:52 2001
> @@ -148,6 +148,9 @@
> * procfs is always supported now. (JT)
> * 12/01/2001 - avoided flushing logical volume in case of shrinking
> * because of unecessary overhead in case of heavy updates
> + * 05/04/2001 - lvm_map bugs: don't use b_blocknr/b_dev in lvm_map, it
> + * destroys stacking devices. call b_end_io on failed maps.
> + * (Jens Axboe)
> *
> */
>
> @@ -1480,14 +1483,14 @@
> */
> static int lvm_map(struct buffer_head *bh, int rw)
> {
> - int minor = MINOR(bh->b_dev);
> + int minor = MINOR(bh->b_rdev);
> int ret = 0;
> ulong index;
> ulong pe_start;
> ulong size = bh->b_size >> 9;
> - ulong rsector_tmp = bh->b_blocknr * size;
> + ulong rsector_tmp = bh->b_rsector;
> ulong rsector_sav;
> - kdev_t rdev_tmp = bh->b_dev;
> + kdev_t rdev_tmp = bh->b_rdev;
> kdev_t rdev_sav;
> vg_t *vg_this = vg[VG_BLK(minor)];
> lv_t *lv = vg_this->lv[LV_BLK(minor)];
> @@ -1676,8 +1679,12 @@
> */
> static int lvm_make_request_fn(request_queue_t *q,
> int rw,
> - struct buffer_head *bh) {
> - return (lvm_map(bh, rw) < 0) ? 0 : 1;
> + struct buffer_head *bh)
> +{
> + int ret = lvm_map(bh, rw);
> + if (ret)
> + bh->b_end_io(bh, test_bit(BH_Uptodate, &bh->b_state));
> + return ret;
> }
>
>

*** Software bugs are stupid.
Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen Sistina Software Inc.
Senior Consultant/Developer Am Sonnenhang 11
56242 Marienrachdorf
Germany
Mauelshagen@Sistina.com +49 2626 141200
FAX 924446
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