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    Subject[PATCH 024 of 35] Allow request bio list not to end with NULL

    If we are going to share a bio between requests, then the
    last bio in a list may not point to NULL, but may point to
    the next bio in a different list.
    So instead of testing if ->bi_next is NULL, test if the bio
    matches rq->biotail.

    Signed-off-by: Neil Brown <neilb@suse.de>

    ### Diffstat output
    ./block/ll_rw_blk.c | 8 ++++----
    ./drivers/block/cciss.c | 16 +++++++++-------
    ./drivers/block/cpqarray.c | 18 ++++++++----------
    ./include/linux/blkdev.h | 5 +++--
    4 files changed, 24 insertions(+), 23 deletions(-)

    diff .prev/block/ll_rw_blk.c ./block/ll_rw_blk.c
    --- .prev/block/ll_rw_blk.c 2007-07-31 11:21:07.000000000 +1000
    +++ ./block/ll_rw_blk.c 2007-07-31 11:21:14.000000000 +1000
    @@ -1196,13 +1196,10 @@ EXPORT_SYMBOL(blk_dump_rq_flags);
    void blk_recount_segments(struct request_queue *q, struct bio *bio)
    {
    struct request rq;
    - struct bio *nxt = bio->bi_next;
    rq.q = q;
    rq.bio = rq.biotail = bio;
    rq.first_offset = 0;
    - bio->bi_next = NULL;
    blk_recalc_rq_segments(&rq);
    - bio->bi_next = nxt;
    bio->bi_phys_segments = rq.nr_phys_segments;
    bio->bi_hw_segments = rq.nr_hw_segments;
    bio->bi_flags |= (1 << BIO_SEG_VALID);
    @@ -3416,7 +3413,10 @@ static int __end_that_request_first(stru
    int nbytes;

    if (nr_bytes >= bio->bi_size) {
    - req->bio = bio->bi_next;
    + if (req->bio == req->biotail)
    + req->bio = NULL;
    + else
    + req->bio = bio->bi_next;
    nbytes = bio->bi_size;
    if (!ordered_bio_endio(req, bio, error))
    bio_endio(bio, error);
    diff .prev/drivers/block/cciss.c ./drivers/block/cciss.c
    --- .prev/drivers/block/cciss.c 2007-07-31 11:20:51.000000000 +1000
    +++ ./drivers/block/cciss.c 2007-07-31 11:21:14.000000000 +1000
    @@ -1187,15 +1187,17 @@ static int cciss_ioctl(struct inode *ino
    }
    }

    -static inline void complete_buffers(struct bio *bio, int status)
    +static inline void complete_buffers(struct request *req, int status)
    {
    - while (bio) {
    - struct bio *xbh = bio->bi_next;
    - int nr_sectors = bio_sectors(bio);
    + while (req->bio) {
    + struct bio *bio = req->bio;
    +
    + if (bio == req->biotail)
    + req->bio = NULL;
    + else
    + req->bio = bio->bi_next;

    - bio->bi_next = NULL;
    bio_endio(bio, status ? 0 : -EIO);
    - bio = xbh;
    }
    }

    @@ -1264,7 +1266,7 @@ static void cciss_softirq_done(struct re
    pci_unmap_page(h->pdev, temp64.val, cmd->SG[i].Len, ddir);
    }

    - complete_buffers(rq->bio, (rq->errors == 0));
    + complete_buffers(rq, (rq->errors == 0));

    if (blk_fs_request(rq)) {
    const int rw = rq_data_dir(rq);
    diff .prev/drivers/block/cpqarray.c ./drivers/block/cpqarray.c
    --- .prev/drivers/block/cpqarray.c 2007-07-31 11:20:51.000000000 +1000
    +++ ./drivers/block/cpqarray.c 2007-07-31 11:21:14.000000000 +1000
    @@ -166,7 +166,6 @@ static void start_io(ctlr_info_t *h);

    static inline void addQ(cmdlist_t **Qptr, cmdlist_t *c);
    static inline cmdlist_t *removeQ(cmdlist_t **Qptr, cmdlist_t *c);
    -static inline void complete_buffers(struct bio *bio, int ok);
    static inline void complete_command(cmdlist_t *cmd, int timeout);

    static irqreturn_t do_ida_intr(int irq, void *dev_id);
    @@ -979,18 +978,17 @@ static void start_io(ctlr_info_t *h)
    }
    }

    -static inline void complete_buffers(struct bio *bio, int ok)
    +static inline void complete_buffers(struct request *req, int ok)
    {
    - struct bio *xbh;
    - while(bio) {
    - int nr_sectors = bio_sectors(bio);
    + while (req->bio) {
    + struct bio *bio = req->bio;

    - xbh = bio->bi_next;
    - bio->bi_next = NULL;
    + if (bio == req->biotail)
    + req->bio = NULL;
    + else
    + req->bio = bio->bi_next;

    bio_endio(bio, ok ? 0 : -EIO);
    -
    - bio = xbh;
    }
    }
    /*
    @@ -1030,7 +1028,7 @@ static inline void complete_command(cmdl
    pci_unmap_page(hba[cmd->ctlr]->pci_dev, cmd->req.sg[i].addr,
    cmd->req.sg[i].size, ddir);

    - complete_buffers(rq->bio, ok);
    + complete_buffers(rq, ok);

    if (blk_fs_request(rq)) {
    const int rw = rq_data_dir(rq);
    diff .prev/include/linux/blkdev.h ./include/linux/blkdev.h
    --- .prev/include/linux/blkdev.h 2007-07-31 11:21:07.000000000 +1000
    +++ ./include/linux/blkdev.h 2007-07-31 11:21:14.000000000 +1000
    @@ -660,12 +660,13 @@ struct req_iterator {
    };
    #define rq_for_each_segment(rq, _iter, bvec) \
    for (_iter.bio = (rq)->bio, _iter.offset = (rq)->first_offset; \
    - _iter.bio; \
    + _iter.bio && _iter.bio != rq->biotail->bi_next; \
    _iter.bio = _iter.bio->bi_next, _iter.offset = 0) \
    bio_for_each_segment_offset(bvec, _iter.bio, _iter.i, \
    _iter.offset)

    -#define rq_iter_last(rq, _iter) (_iter.bio->bi_next == NULL && \
    +#define rq_iter_last(rq, _iter) ((_iter.bio->bi_next == NULL || \
    + _iter.bio == rq->biotail) && \
    _iter.i.i == _iter.bio->bi_vcnt - 1)

    extern int blk_register_queue(struct gendisk *disk);
    -
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