lustre/kernel_patches/patches/raid5-merge-ios.patch

   1 Merge IO requests to try and get larger requests on underlying drives.
   2
   3 Index: linux-2.6.9/drivers/md/raid5.c
   4 ===================================================================
   5 --- linux-2.6.9.orig/drivers/md/raid5.c 2006-05-22 00:10:04.000000000 +0400
   6 +++ linux-2.6.9/drivers/md/raid5.c      2006-05-22 00:10:06.000000000 +0400
   7 @@ -934,6 +934,26 @@ static void add_stripe_bio (struct strip
   8         }
   9  }
  10
  11 +/*
  12 + * The whole idea is to collect all bio's and then issue them
  13 + * disk by disk to assist merging a bit -bzzz
  14 + */
  15 +static void raid5_flush_bios(raid5_conf_t *conf, struct bio *bios[], int raid_disks)
  16 +{
  17 +       struct bio *bio, *nbio;
  18 +       int i;
  19 +
  20 +       for (i = 0; i < raid_disks; i++) {
  21 +               bio = bios[i];
  22 +               while (bio) {
  23 +                       nbio = bio->bi_next;
  24 +                       bio->bi_next = NULL;
  25 +                       generic_make_request(bio);
  26 +                       bio = nbio;
  27 +               }
  28 +               bios[i] = NULL;
  29 +       }
  30 +}
  31
  32  /*
  33   * handle_stripe - do things to a stripe.
  34 @@ -953,7 +973,7 @@ static void add_stripe_bio (struct strip
  35   *
  36   */
  37
  38 -static void handle_stripe(struct stripe_head *sh)
  39 +static void handle_stripe(struct stripe_head *sh, struct bio *bios[])
  40  {
  41         raid5_conf_t *conf = sh->raid_conf;
  42         int disks = conf->raid_disks;
  43 @@ -1376,7 +1396,11 @@ static void handle_stripe(struct stripe_
  44                         bi->bi_size = STRIPE_SIZE;
  45                         bi->bi_next = NULL;
  46                         atomic_inc(&conf->out_reqs_in_queue);
  47 -                       generic_make_request(bi);
  48 +                       if (bios) {
  49 +                               bi->bi_next = bios[i];
  50 +                               bios[i] = bi;
  51 +                       } else
  52 +                               generic_make_request(bi);
  53                 } else {
  54                         PRINTK("skip op %ld on disc %d for sector %llu\n",
  55                                 bi->bi_rw, i, (unsigned long long)sh->sector);
  56 @@ -1501,6 +1525,7 @@ static int make_request (request_queue_t
  57         int sectors_per_chunk = conf->chunk_size >> 9;
  58         int stripes_per_chunk, sectors_per_block;
  59         int sectors_per_stripe;
  60 +       struct bio *bios[MD_SB_DISKS];
  61         int i, j;
  62
  63         atomic_inc(&conf->in_reqs_in_queue);
  64 @@ -1530,6 +1555,7 @@ static int make_request (request_queue_t
  65         sector_div(block, sectors_per_block);
  66         sectors = bi->bi_size >> 9;
  67
  68 +       memset(&bios, 0, sizeof(bios));
  69  repeat:
  70         stripe = block * sectors_per_block / data_disks;
  71         b_sector = stripe * data_disks;
  72 @@ -1549,9 +1575,17 @@ repeat:
  73                         new_sector = raid5_compute_sector(r_sector, raid_disks,
  74                                                         data_disks, &dd_idx,
  75                                                         &pd_idx, conf);
  76 -                       if (sh == NULL)
  77 -                               sh = get_active_stripe(conf, new_sector, pd_idx,
  78 -                                                       (bi->bi_rw&RWA_MASK));
  79 +                       if (sh == NULL) {
  80 +                               /* first, try to get stripe w/o blocking
  81 +                                * if we can't, then it's time to submit
  82 +                                * all collected bio's in order to free
  83 +                                * some space in the cache -bzzz */
  84 +                               sh = get_active_stripe(conf, new_sector, pd_idx, 1);
  85 +                               if (!sh && !(bi->bi_rw&RWA_MASK)) {
  86 +                                       raid5_flush_bios(conf, bios, raid_disks);
  87 +                                       sh = get_active_stripe(conf, new_sector, pd_idx, 0);
  88 +                               }
  89 +                       }
  90                         if (sh) {
  91                                 add_stripe_bio(sh, bi, dd_idx, (bi->bi_rw&RW_MASK));
  92                         } else {
  93 @@ -1571,7 +1605,7 @@ repeat:
  94                 }
  95                 if (sh) {
  96                         raid5_plug_device(conf);
  97 -                       handle_stripe(sh);
  98 +                       handle_stripe(sh, bios);
  99                         release_stripe(sh);
 100                         sh = NULL;
 101                 }
 102 @@ -1581,6 +1615,9 @@ repeat:
 103         if (sectors > 0)
 104                 goto repeat;
 105
 106 +       /* now flush all bio's */
 107 +       raid5_flush_bios(conf, bios, raid_disks);
 108 +
 109         spin_lock_irq(&conf->device_lock);
 110         if (--bi->bi_phys_segments == 0) {
 111                 int bytes = bi->bi_size;
 112 @@ -1636,7 +1673,7 @@ static int sync_request (mddev_t *mddev,
 113         clear_bit(STRIPE_INSYNC, &sh->state);
 114         spin_unlock(&sh->lock);
 115
 116 -       handle_stripe(sh);
 117 +       handle_stripe(sh, NULL);
 118         release_stripe(sh);
 119
 120         return STRIPE_SECTORS;
 121 @@ -1685,7 +1722,7 @@ static void raid5d (mddev_t *mddev)
 122
 123                 handled++;
 124                 atomic_inc(&conf->handled_in_raid5d);
 125 -               handle_stripe(sh);
 126 +               handle_stripe(sh, NULL);
 127                 release_stripe(sh);
 128
 129                 spin_lock_irq(&conf->device_lock);