>>>>> "Seunguk" == Seunguk Shin <seunguk.shin@xxxxxxxxxxx> writes:
Seunguk,
Thanks for tracking this down. Instead of explicitly coding around the
issue in raid0/raid10/linear I would prefer to fix bio_split(). It seems
like a deficiency in the interface that it does not handle this
transparently.
Do you have a reproducible test case? If so it would be great if you
could try the following patch and let us know the results.
Thank you!
--
Martin K. Petersen Oracle Linux Engineering
commit 779e6b55da74108460baa8194d82806c4d7db523
Author: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Date: Mon Jul 20 08:05:30 2015 -0400
block: Do a full clone when splitting discard bios
Commit 20d0189b1012 "block: Introduce new bio_split()" permits sharing
the bio_vec between the two resulting bios. That's fine for read/write
requests where the bio_vec is immutable. For discards, however, we need
to be able to attach a payload and update the bio_vec so the page can
get mapped to a scatterlist entry. Therefore the bio_vec can not be
shared when splitting discards and we must do a full clone.
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Reported-by: Seunguk Shin <seunguk.shin@xxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v3.14+
diff --git a/block/bio.c b/block/bio.c
index 2a00d349cd68..616b0e6f910a 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1842,7 +1842,15 @@ struct bio *bio_split(struct bio *bio, int sectors,
BUG_ON(sectors <= 0);
BUG_ON(sectors >= bio_sectors(bio));
- split = bio_clone_fast(bio, gfp, bs);
+ /*
+ * Discards need a mutable bio_vec to accommodate the payload
+ * required by the DSM TRIM and UNMAP commands.
+ */
+ if (bio->bi_rw & REQ_DISCARD)
+ split = bio_clone_bioset(bio, gfp, bs);
+ else
+ split = bio_clone_fast(bio, gfp, bs);
+
if (!split)
return NULL;
--
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