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Subject[PATCH v3 11/16] block: Only clone bio vecs that are in use
Date
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@google.com>
Change-Id: I71971827a623ce90626fa4a09b07f95f875ad890
---
drivers/block/rbd.c | 2 +-
drivers/md/dm.c | 5 ++---
fs/bio.c | 13 +++++++------
3 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 11777b4..c1f8a8fe 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -729,7 +729,7 @@ 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 3f3c26e..193fb19 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1057,11 +1057,10 @@ 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 a62b5b6..a85239f 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -441,8 +441,9 @@ EXPORT_SYMBOL(bio_phys_segments);
*/
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,
@@ -451,10 +452,10 @@ 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);

@@ -469,7 +470,7 @@ EXPORT_SYMBOL(__bio_clone);
struct bio *bio_clone_bioset(struct bio *bio, gfp_t gfp_mask,
struct bio_set *bs)
{
- struct bio *b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, bs);
+ struct bio *b = bio_alloc_bioset(gfp_mask, bio_segments(bio), bs);

if (!b)
return NULL;
@@ -499,7 +500,7 @@ EXPORT_SYMBOL(bio_clone);

struct bio *bio_clone_kmalloc(struct bio *bio, gfp_t gfp_mask)
{
- struct bio *b = bio_kmalloc(gfp_mask, bio->bi_max_vecs);
+ struct bio *b = bio_kmalloc(gfp_mask, bio_segments(bio));

if (!b)
return NULL;
--
1.7.9.3.327.g2980b


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