On Friday 21 January 2005 9:01 am, Kevin Corry wrote:
> On Friday 21 January 2005 8:47 am, Lars Marowsky-Bree wrote:
> > This looks like md on DM breakage, which Jens has just fixed in our
> > kernel. I'm not sure whether he has submitted it upstream yet, but you
> > can give it a try.
> >
> > Does the attached patch apply & fix the problem for you?
> >
> > If md resides on top of a driver using bio_clone() (such as dm), it
> > will oops the kernel due to md submitting a botched bio that has a
> > veclist but doesn't have bio->bi_max_vecs set.
>
> Is there a specific scenario that causes the kernel to oops if an MD device
> is made of DM devices? EVMS has been using this kind of configuration for a
> couple years, and we've never noticed a problem with it. Also, syrius
> mentioned on IRC that this problem only started occurring with -ac10, and
> that -ac8 worked fine. I'm checking out the diffs between those two
> versions to see what else might have changed.
Ok, here's the excerpt from the -ac10 patch that probably exposed the bug in
MD. So it looks like a cloned bio no longer uses the original bio's bvec,
which makes Lars' explination make a bit more sense. :) So, try Lars' patch
with your -ac10 kernel and see if that fixes it. If so, we should forward
that to Alan and make sure he includes it. I'll also check the latest -mm and
-bk to see if these patches need to be merged upstream before 2.6.11 final.
diff -Naurp linux-2.6.10-ac9/fs/bio.c linux-2.6.10-ac10/fs/bio.c
--- linux-2.6.10-ac9/fs/bio.c 2004-12-24 15:35:00.000000000 -0600
+++ linux-2.6.10-ac10/fs/bio.c 2005-01-21 08:50:27.000000000 -0600
@@ -98,12 +98,7 @@ void bio_destructor(struct bio *bio)
BIO_BUG_ON(pool_idx >= BIOVEC_NR_POOLS);
- /*
- * cloned bio doesn't own the veclist
- */
- if (!bio_flagged(bio, BIO_CLONED))
- mempool_free(bio->bi_io_vec, bp->pool);
-
+ mempool_free(bio->bi_io_vec, bp->pool);
mempool_free(bio, bio_pool);
}
@@ -210,7 +205,9 @@ inline int bio_hw_segments(request_queue
*/
inline void __bio_clone(struct bio *bio, struct bio *bio_src)
{
- bio->bi_io_vec = bio_src->bi_io_vec;
+ request_queue_t *q = bdev_get_queue(bio_src->bi_bdev);
+
+ memcpy(bio->bi_io_vec, bio_src->bi_io_vec, bio_src->bi_max_vecs *
sizeof(struct bio_vec));
bio->bi_sector = bio_src->bi_sector;
bio->bi_bdev = bio_src->bi_bdev;
@@ -222,21 +219,9 @@ inline void __bio_clone(struct bio *bio,
* for the clone
*/
bio->bi_vcnt = bio_src->bi_vcnt;
- bio->bi_idx = bio_src->bi_idx;
- if (bio_flagged(bio, BIO_SEG_VALID)) {
- bio->bi_phys_segments = bio_src->bi_phys_segments;
- bio->bi_hw_segments = bio_src->bi_hw_segments;
- bio->bi_flags |= (1 << BIO_SEG_VALID);
- }
bio->bi_size = bio_src->bi_size;
-
- /*
- * cloned bio does not own the bio_vec, so users cannot fiddle with
- * it. clear bi_max_vecs and clear the BIO_POOL_BITS to make this
- * apparent
- */
- bio->bi_max_vecs = 0;
- bio->bi_flags &= (BIO_POOL_MASK - 1);
+ bio_phys_segments(q, bio);
+ bio_hw_segments(q, bio);
}
/**
@@ -248,7 +233,7 @@ inline void __bio_clone(struct bio *bio,
*/
struct bio *bio_clone(struct bio *bio, int gfp_mask)
{
- struct bio *b = bio_alloc(gfp_mask, 0);
+ struct bio *b = bio_alloc(gfp_mask, bio->bi_max_vecs);
if (b)
__bio_clone(b, bio);
--
Kevin Corry
kevcorry@xxxxxxxxxx
http://evms.sourceforge.net/
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