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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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