src/patches/suse-2.6.27.31/patches.suse/dm-barrier-single-device

   1 From: Andi Kleen <ak@suse.de>
   2 Subject: Implement barrier support for single device DM devices
   3 Patch-mainline: 2.6.28
   4 References: FATE#304489
   5
   6 This patch implements barrier support in DM for the common case of dm linear
   7 just remapping a single underlying device. In this case we can safely
   8 pass the barrier through because there can be no reordering between
   9 devices.
  10
  11 Signed-off-by: Andi Kleen <ak@suse.de>
  12
  13 This patch is slightly different from the one which made it to the mainline.
  14 But this is not replaced by that as it would break kABI. The mainline
  15 commit is ab4c1424882be9cd70b89abf2b484add355712fa
  16
  17 Acked-by: Nikanth Karthikesan <knikanth@suse.de>
  18
  19 ---
  20  drivers/md/dm-linear.c |    1 +
  21  drivers/md/dm-table.c  |   26 +++++++++++++++++++++++++-
  22  drivers/md/dm.c        |   14 ++++----------
  23  drivers/md/dm.h        |    2 ++
  24  4 files changed, 32 insertions(+), 11 deletions(-)
  25
  26 Index: linux-2.6.27/drivers/md/dm.c
  27 ===================================================================
  28 --- linux-2.6.27.orig/drivers/md/dm.c
  29 +++ linux-2.6.27/drivers/md/dm.c
  30 @@ -1149,7 +1149,11 @@ static int __split_bio(struct mapped_dev
  31         ci.map = dm_get_table(md);
  32         if (unlikely(!ci.map))
  33                 return -EIO;
  34 -
  35 +       if (unlikely(bio_barrier(bio) && !dm_table_barrier_ok(ci.map))) {
  36 +               bio_endio(bio, -EOPNOTSUPP);
  37 +               dm_table_put(ci.map);
  38 +               return 0;
  39 +       }
  40         ci.md = md;
  41         ci.bio = bio;
  42         ci.io = alloc_io(md);
  43 @@ -1232,15 +1236,6 @@ static int _dm_request(struct request_qu
  44         int rw = bio_data_dir(bio);
  45         struct mapped_device *md = q->queuedata;
  46
  47 -       /*
  48 -        * There is no use in forwarding any barrier request since we can't
  49 -        * guarantee it is (or can be) handled by the targets correctly.
  50 -        */
  51 -       if (unlikely(bio_barrier(bio))) {
  52 -               bio_endio(bio, -EOPNOTSUPP);
  53 -               return 0;
  54 -       }
  55 -
  56         down_read(&md->io_lock);
  57
  58         disk_stat_inc(dm_disk(md), ios[rw]);
  59 Index: linux-2.6.27/drivers/md/dm.h
  60 ===================================================================
  61 --- linux-2.6.27.orig/drivers/md/dm.h
  62 +++ linux-2.6.27/drivers/md/dm.h
  63 @@ -66,6 +66,8 @@ void dm_table_unplug_all(struct dm_table
  64   * To check the return value from dm_table_find_target().
  65   */
  66  #define dm_target_is_valid(t) ((t)->table)
  67 +int dm_table_barrier_ok(struct dm_table *t);
  68 +void dm_table_support_barrier(struct dm_table *t);
  69
  70  /*-----------------------------------------------------------------
  71   * A registry of target types.
  72 Index: linux-2.6.27/drivers/md/dm-linear.c
  73 ===================================================================
  74 --- linux-2.6.27.orig/drivers/md/dm-linear.c
  75 +++ linux-2.6.27/drivers/md/dm-linear.c
  76 @@ -52,6 +52,7 @@ static int linear_ctr(struct dm_target *
  77                 ti->error = "dm-linear: Device lookup failed";
  78                 goto bad;
  79         }
  80 +       dm_table_support_barrier(ti->table);
  81
  82         ti->private = lc;
  83         return 0;
  84 Index: linux-2.6.27/drivers/md/dm-table.c
  85 ===================================================================
  86 --- linux-2.6.27.orig/drivers/md/dm-table.c
  87 +++ linux-2.6.27/drivers/md/dm-table.c
  88 @@ -38,6 +38,9 @@ struct dm_table {
  89         sector_t *highs;
  90         struct dm_target *targets;
  91
  92 +       unsigned single_device : 1;
  93 +       unsigned barrier_supported : 1;
  94 +
  95         /*
  96          * Indicates the rw permissions for the new logical
  97          * device.  This should be a combination of FMODE_READ
  98 @@ -532,12 +535,21 @@ EXPORT_SYMBOL_GPL(dm_set_device_limits);
  99  int dm_get_device(struct dm_target *ti, const char *path, sector_t start,
 100                   sector_t len, int mode, struct dm_dev **result)
 101  {
 102 -       int r = __table_get_device(ti->table, ti, path,
 103 +       struct dm_table *t = ti->table;
 104 +       int r = __table_get_device(t, ti, path,
 105                                    start, len, mode, result);
 106
 107         if (!r)
 108                 dm_set_device_limits(ti, (*result)->bdev);
 109
 110 +       if (!r) {
 111 +               /* Only got single device? */
 112 +               if (t->devices.next->next == &t->devices)
 113 +                       t->single_device = 1;
 114 +               else
 115 +                       t->single_device = 0;
 116 +       }
 117 +
 118         return r;
 119  }
 120
 121 @@ -1050,6 +1062,16 @@ struct mapped_device *dm_table_get_md(st
 122         return t->md;
 123  }
 124
 125 +int dm_table_barrier_ok(struct dm_table *t)
 126 +{
 127 +       return t->single_device && t->barrier_supported;
 128 +}
 129 +
 130 +void dm_table_support_barrier(struct dm_table *t)
 131 +{
 132 +       t->barrier_supported = 1;
 133 +}
 134 +
 135  EXPORT_SYMBOL(dm_vcalloc);
 136  EXPORT_SYMBOL(dm_get_device);
 137  EXPORT_SYMBOL(dm_put_device);
 138 @@ -1060,3 +1082,5 @@ EXPORT_SYMBOL(dm_table_get_md);
 139  EXPORT_SYMBOL(dm_table_put);
 140  EXPORT_SYMBOL(dm_table_get);
 141  EXPORT_SYMBOL(dm_table_unplug_all);
 142 +EXPORT_SYMBOL(dm_table_barrier_ok);
 143 +EXPORT_SYMBOL(dm_table_support_barrier);