bcache creates large bios internally, and then splits them according to
the device requirements before it sends them down. If a lower level
device tries to clone the bio, and the original bio had more than
BIO_MAX_PAGES, the clone will fail unecessarily.
We can fix this by only cloning the bio vecs that are actually in use.
Signed-off-by: Kent Overstreet <koverstreet@xxxxxxxxxx>
CC: Jens Axboe <axboe@xxxxxxxxx>
CC: Alasdair Kergon <agk@xxxxxxxxxx>
CC: Sage Weil <sage@xxxxxxxxxxx>
---
drivers/block/rbd.c | 2 +-
drivers/md/dm.c | 5 ++---
fs/bio.c | 15 ++++++++++-----
3 files changed, 13 insertions(+), 9 deletions(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 63e5852..5c3457f 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -734,7 +734,7 @@ static struct bio *bio_chain_clone(struct bio **old, struct bio **next,
}
while (old_chain && (total < len)) {
- tmp = bio_kmalloc(gfpmask, old_chain->bi_max_vecs);
+ tmp = bio_kmalloc(gfpmask, bio_segments(old_chain));
if (!tmp)
goto err_out;
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index a3c38b9..3aeb108 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1080,11 +1080,10 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector,
{
struct bio *clone;
- clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs);
+ clone = bio_alloc_bioset(GFP_NOIO, bv_count, bs);
__bio_clone(clone, bio);
clone->bi_sector = sector;
- clone->bi_idx = idx;
- clone->bi_vcnt = idx + bv_count;
+ clone->bi_vcnt = bv_count;
clone->bi_size = to_bytes(len);
clone->bi_flags &= ~(1 << BIO_SEG_VALID);
diff --git a/fs/bio.c b/fs/bio.c
index a58c3c6..3f43e50 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -450,11 +450,16 @@ EXPORT_SYMBOL(bio_phys_segments);
* Clone a &bio. Caller will own the returned bio, but not
* the actual data it points to. Reference count of returned
* bio will be one.
+ *
+ * We don't clone the entire bvec, just the part from bi_idx to b_vcnt
+ * (i.e. what the bio currently points to, so the new bio is still
+ * equivalent to the old bio).
*/
void __bio_clone(struct bio *bio, struct bio *bio_src)
{
- memcpy(bio->bi_io_vec, bio_src->bi_io_vec,
- bio_src->bi_max_vecs * sizeof(struct bio_vec));
+ memcpy(bio->bi_io_vec,
+ bio_iovec(bio_src),
+ bio_segments(bio_src) * sizeof(struct bio_vec));
/*
* most users will be overriding ->bi_bdev with a new target,
@@ -463,10 +468,10 @@ void __bio_clone(struct bio *bio, struct bio *bio_src)
bio->bi_sector = bio_src->bi_sector;
bio->bi_bdev = bio_src->bi_bdev;
bio->bi_flags |= 1 << BIO_CLONED;
+ bio->bi_flags &= ~(1 << BIO_SEG_VALID);
bio->bi_rw = bio_src->bi_rw;
- bio->bi_vcnt = bio_src->bi_vcnt;
+ bio->bi_vcnt = bio_segments(bio_src);
bio->bi_size = bio_src->bi_size;
- bio->bi_idx = bio_src->bi_idx;
}
EXPORT_SYMBOL(__bio_clone);
@@ -483,7 +488,7 @@ struct bio *bio_clone_bioset(struct bio *bio, gfp_t gfp_mask,
{
struct bio *b;
- b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, bs);
+ b = bio_alloc_bioset(gfp_mask, bio_segments(bio), bs);
if (!b)
return NULL;
--
1.7.12
--
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