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    Subject[PATCH 10/16] md: satisfy raid5 read requests via raid5_run_ops
    Date
    Use raid5_run_ops to carry out the memory copies for a raid5 read request.

    Changelog:
    * cleanup to_read and to_fill accounting
    * do not fail reads that have reached the cache

    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    ---

    drivers/md/raid5.c | 61 ++++++++++++++++++++++++++--------------------------
    1 files changed, 30 insertions(+), 31 deletions(-)

    diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
    index f8a4522..6bde174 100644
    --- a/drivers/md/raid5.c
    +++ b/drivers/md/raid5.c
    @@ -1998,7 +1998,7 @@ static void handle_stripe5(struct stripe_head *sh)
    int i;
    int syncing, expanding, expanded;
    int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
    - int compute=0, req_compute=0, non_overwrite=0;
    + int to_fill=0, compute=0, req_compute=0, non_overwrite=0;
    int failed_num=0;
    struct r5dev *dev;
    unsigned long pending=0;
    @@ -2022,37 +2022,29 @@ static void handle_stripe5(struct stripe_head *sh)
    dev = &sh->dev[i];
    clear_bit(R5_Insync, &dev->flags);

    - PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
    - i, dev->flags, dev->toread, dev->towrite, dev->written);
    - /* maybe we can reply to a read */
    - if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
    - struct bio *rbi, *rbi2;
    - PRINTK("Return read for disc %d\n", i);
    - spin_lock_irq(&conf->device_lock);
    - rbi = dev->toread;
    - dev->toread = NULL;
    - if (test_and_clear_bit(R5_Overlap, &dev->flags))
    - wake_up(&conf->wait_for_overlap);
    - spin_unlock_irq(&conf->device_lock);
    - while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
    - copy_data(0, rbi, dev->page, dev->sector);
    - rbi2 = r5_next_bio(rbi, dev->sector);
    - spin_lock_irq(&conf->device_lock);
    - if (--rbi->bi_phys_segments == 0) {
    - rbi->bi_next = return_bi;
    - return_bi = rbi;
    - }
    - spin_unlock_irq(&conf->device_lock);
    - rbi = rbi2;
    - }
    - }
    + PRINTK("check %d: state 0x%lx toread %p read %p write %p written %p\n",
    + i, dev->flags, dev->toread, dev->read, dev->towrite, dev->written);
    +
    + /* maybe we can request a biofill operation
    + *
    + * new wantfill requests are only permitted while
    + * STRIPE_OP_BIOFILL is clear
    + */
    + if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
    + !test_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
    + set_bit(R5_Wantfill, &dev->flags);

    /* now count some things */
    if (test_bit(R5_LOCKED, &dev->flags)) locked++;
    if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
    +
    + if (test_bit(R5_Wantfill, &dev->flags))
    + to_fill++;
    + else if (dev->toread)
    + to_read++;
    +
    if (test_bit(R5_Wantcompute, &dev->flags)) BUG_ON(++compute > 1);

    - if (dev->toread) to_read++;
    if (dev->towrite) {
    to_write++;
    if (!test_bit(R5_OVERWRITE, &dev->flags))
    @@ -2073,9 +2065,13 @@ static void handle_stripe5(struct stripe_head *sh)
    set_bit(R5_Insync, &dev->flags);
    }
    rcu_read_unlock();
    +
    + if (to_fill && !test_and_set_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
    + sh->ops.count++;
    +
    PRINTK("locked=%d uptodate=%d to_read=%d"
    - " to_write=%d failed=%d failed_num=%d\n",
    - locked, uptodate, to_read, to_write, failed, failed_num);
    + " to_write=%d to_fill=%d failed=%d failed_num=%d\n",
    + locked, uptodate, to_read, to_write, to_fill, failed, failed_num);
    /* check if the array has lost two devices and, if so, some requests might
    * need to be failed
    */
    @@ -2127,9 +2123,12 @@ static void handle_stripe5(struct stripe_head *sh)
    bi = bi2;
    }

    - /* fail any reads if this device is non-operational */
    - if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
    - test_bit(R5_ReadError, &sh->dev[i].flags)) {
    + /* fail any reads if this device is non-operational and
    + * the data has not reached the cache yet.
    + */
    + if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
    + (!test_bit(R5_Insync, &sh->dev[i].flags) ||
    + test_bit(R5_ReadError, &sh->dev[i].flags))) {
    bi = sh->dev[i].toread;
    sh->dev[i].toread = NULL;
    if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
    -
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