On Thursday August 7, akpm@osdl.org wrote:
> Neil Brown <neilb@cse.unsw.edu.au> wrote:
>
> > So I guess the finger points generally in the direction of raid5.
> > Now I've just got to figure if it is a bug in r5, or some assumption
> > that it makes that is no longer valid (I was briefly suspicious of
> > PF_READAHEAD which could have made a real mess of raid5, but that
> > wouldn't have this symptom)
>
> The PF_READAHEAD things was a huge bug. Make sure that it is fixed before
> proceeding. Linus's tree has the fix.
I found it. It was read-ahead related, but nothing to do with
PF_READAHEAD.
With this patch, my test ran to completion instead of dying at about
th 20% mark.
NeilBrown
=================================================================
Disable raid5 handling of read-ahead
raid5 trys to honour RWA_MASK, but messes it up and can return bad data.
Just ignore RWA_MASK for now.
----------- Diffstat output ------------
./drivers/md/raid5.c | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)
diff ./drivers/md/raid5.c~current~ ./drivers/md/raid5.c
--- ./drivers/md/raid5.c~current~ 2003-08-08 14:37:00.000000000 +1000
+++ ./drivers/md/raid5.c 2003-08-08 14:37:19.000000000 +1000
@@ -1326,7 +1326,7 @@ static int make_request (request_queue_t
(unsigned long long)new_sector,
(unsigned long long)logical_sector);
- sh = get_active_stripe(conf, new_sector, pd_idx, (bi->bi_rw&RWA_MASK));
+ sh = get_active_stripe(conf, new_sector, pd_idx, 0/*(bi->bi_rw&RWA_MASK)*/);
if (sh) {
add_stripe_bio(sh, bi, dd_idx, (bi->bi_rw&RW_MASK));
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