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    SubjectRe: [Drbd-dev] [PATCH v3 06/26] block: Add bio_end_sector()
    On Mon, Sep 24, 2012 at 03:34:46PM -0700, Kent Overstreet wrote:
    > Just a little convenience macro - main reason to add it now is preparing
    > for immutable bio vecs, it'll reduce the size of the patch that puts
    > bi_sector/bi_size/bi_idx into a struct bvec_iter.


    For the DRBD part:

    > diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
    > index 01b2ac6..d90a1fd 100644
    > --- a/drivers/block/drbd/drbd_req.c
    > +++ b/drivers/block/drbd/drbd_req.c
    > @@ -1144,7 +1144,7 @@ void drbd_make_request(struct request_queue *q, struct bio *bio)
    > /* to make some things easier, force alignment of requests within the
    > * granularity of our hash tables */
    > s_enr = bio->bi_sector >> HT_SHIFT;
    > - e_enr = bio->bi_size ? (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT : s_enr;
    > + e_enr = (bio_end_sector(bio) - 1) >> HT_SHIFT;

    You ignored the bio->bi_size ? : ;

    #define bio_end_sector(bio) ((bio)->bi_sector + bio_sectors(bio))
    which turns out (bio->bi_sector + (bio->bi_size >> 9))

    Note that bi_size may be 0, bio_end_sector(bio)-1 then is bi_sector -1,
    for an empty flush with bi_sector == 0, this ends up as (sector_t)-1ULL,
    and this code path breaks horribly.


    + e_enr = bio->bi_size ? (bio_end_sector(bio) - 1) >> HT_SHIFT : s_enr;


    Thanks,
    Lars


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