> Hi, all. I've just noticed that MD (with raid0) is broken in
> 2.3.33. I get the following message:
> Got md request, not good...
>
> This seems to be because DEVICE_REQUEST() is being called (which is
> defined to be do_md_request(). Perhaps the block device request queue
> changes is to blame? I didn't have this problem with 2.3.31.
>
> Anyone got a patch to fix this?
Not a patch, but I did get it working. Yesterday I beat the living
_tar_ out of my box and it works perfectly.
The trouble (afaikt) is two fold..
make_request() pulls the wrong queue for a raid device via
q = get_queue(bh->b_dev)
and then does
if( !q->plugged )
(q->request_fn)(q);
which leads directly to do_md_request().
ll_rw_block() contains..
for (i = 0; i < nr; i++) {
set_bit(BH_Req, &bh[i]->b_state);
#ifdef CONFIG_BLK_DEV_MD
if (MAJOR(bh[i]->b_dev) == MD_MAJOR) {
md_make_request(bh[i], rw);
continue;
}
#endif
__make_request(q, MAJOR(bh[i]->b_rdev), rw, bh[i]);
}
.. ie it wants to substitute it's own handling where there is a
handler (raid1/5), but in md_make_request() at the point where
you fall through, you hit make_request() instead of the intended
__make_request().
What I did (because get_queue() and __make_request() are static)
was to clone make_request() and call it make_request_redirect().
It is identical to make_request except it does..
q = get_queue(bh->b_rdev) << remember this 'difference'
The workaround (bandaid) in md_make_request() looks like this.
err = mddev->pers->make_request(mddev, rw, bh);
} else {
extern void make_request_redirect(int,int,struct buffer_head *);
make_request_redirect (MAJOR(bh->b_rdev), rw, bh);
err = 0;
}
Comment out the printk in do_md_request(), apply the same bandaid to
raid1.c and raid5.c and you're done.
I have one tiiiiny little problem with this 'fix'. If you look at
ll_rw_block() a few lines up from md_make_request(), you'll see..
/* Md remaps blocks now */
bh[i]->b_rdev = bh[i]->b_dev;
I <zzzt> don't get it, but <zzzt> it works. I'll wait for the movie.
-Mike
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