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    Subject[PATCH v4 03/12] block: Add bio_reset()
    Date
    Reusing bios is something that's been highly frowned upon in the past,
    but driver code keeps doing it anyways. If it's going to happen anyways,
    we should provide a generic method.

    This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
    was open coding it, by doing a bio_init() and resetting bi_destructor.

    Signed-off-by: Kent Overstreet <koverstreet@google.com>
    ---
    fs/bio.c | 10 ++++++++++
    include/linux/bio.h | 1 +
    include/linux/blk_types.h | 6 ++++++
    3 files changed, 17 insertions(+), 0 deletions(-)

    diff --git a/fs/bio.c b/fs/bio.c
    index 1c6c8b7..252e253 100644
    --- a/fs/bio.c
    +++ b/fs/bio.c
    @@ -261,6 +261,16 @@ void bio_init(struct bio *bio)
    }
    EXPORT_SYMBOL(bio_init);

    +void bio_reset(struct bio *bio)
    +{
    + /* Clear all flags below BIO_OWNS_VEC */
    + unsigned long flags = bio->bi_flags & (~0UL << BIO_OWNS_VEC);
    +
    + memset(bio, 0, BIO_RESET_BYTES);
    + bio->bi_flags = flags|(1 << BIO_UPTODATE);
    +}
    +EXPORT_SYMBOL(bio_reset);
    +
    /**
    * bio_alloc_bioset - allocate a bio for I/O
    * @gfp_mask: the GFP_ mask given to the slab allocator
    diff --git a/include/linux/bio.h b/include/linux/bio.h
    index 2643589..ba60319 100644
    --- a/include/linux/bio.h
    +++ b/include/linux/bio.h
    @@ -226,6 +226,7 @@ extern void __bio_clone(struct bio *, struct bio *);
    extern struct bio *bio_clone(struct bio *, gfp_t);

    extern void bio_init(struct bio *);
    +extern void bio_reset(struct bio *);

    extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
    extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
    diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
    index 293547e..40411e2 100644
    --- a/include/linux/blk_types.h
    +++ b/include/linux/blk_types.h
    @@ -59,6 +59,10 @@ struct bio {
    unsigned int bi_seg_front_size;
    unsigned int bi_seg_back_size;

    + /*
    + * Everything starting with bi_max_vecs will be preserved by bio_reset()
    + */
    +
    unsigned int bi_max_vecs; /* max bvl_vecs we can hold */

    atomic_t bi_cnt; /* pin count */
    @@ -93,6 +97,8 @@ struct bio {
    struct bio_vec bi_inline_vecs[0];
    };

    +#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
    +
    /*
    * bio flags
    */
    --
    1.7.7.3


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