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SubjectOne more bio for for floppy users in 2.5.33..

I found another major bio-related bug that definitely explains why the
floppy driver generated corruption - any partial request completion would
be totally messed up by the BIO layer (not the floppy driver).

Any other block device driver that did partial request completion might
also be impacted.

I'm still looking at the floppy driver itself - some of the request
completion code is so messed up as to be unreadable, and some of that may
actually be due to trying to work around the bio problem (unsuccessfully,
I may add). So this may not actually fix things for you yet, simply
because the floppy driver itself still does some strange things.

Jens, oops. We should not update the counts by how much was left
uncompleted, but by how much we successfully completed!


# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/09/03 1.582
# Major partial request completion boo-boo in the bio layer.
# This was _bad_. Major floppy corruption, and possibly the reason
# for other block device corruption for any driver that generated
# partial results for a block device request.
# --------------------------------------------
diff -Nru a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
--- a/drivers/block/ll_rw_blk.c Tue Sep 3 10:53:59 2002
+++ b/drivers/block/ll_rw_blk.c Tue Sep 3 10:53:59 2002
@@ -1992,11 +1992,11 @@
* not a complete bvec done
if (unlikely(nsect > nr_sectors)) {
- int residual = (nsect - nr_sectors) << 9;
+ int partial = nr_sectors << 9;

- bio->bi_size -= residual;
- bio_iovec(bio)->bv_offset += residual;
- bio_iovec(bio)->bv_len -= residual;
+ bio->bi_size -= partial;
+ bio_iovec(bio)->bv_offset += partial;
+ bio_iovec(bio)->bv_len -= partial;
blk_recalc_rq_sectors(req, nr_sectors);
return 1;
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