dm: calculate queue limits during resume not load

Currently, device-mapper maintains a separate instance of 'struct
queue_limits' for each table of each device.  When the configuration of
a device is to be changed, first its table is loaded and this structure
is populated, then the device is 'resumed' and the calculated
queue_limits are applied.

This places restrictions on how userspace may process related devices,
where it is often advantageous to 'load' tables for several devices
at once before 'resuming' them together.  As the new queue_limits
only take effect after the 'resume', if they are changing and one
device uses another, the latter must be 'resumed' before the former
may be 'loaded'.

This patch moves the calculation of these queue_limits out of
the 'load' operation into 'resume'.  Since we are no longer
pre-calculating this struct, we no longer need to maintain copies
within our dm structs.

dm_set_device_limits() now passes the 'start' of the device's
data area (aka pe_start) as the 'offset' to blk_stack_limits().

init_valid_queue_limits() is replaced by blk_set_default_limits().

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: martin.petersen@oracle.com
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index a9210bb594e7..f609793a92d0 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1313,7 +1313,8 @@ static void __set_size(struct mapped_device *md, sector_t size)
         mutex_unlock(&md->bdev->bd_inode->i_mutex);
 }
 
-static int __bind(struct mapped_device *md, struct dm_table *t)
+static int __bind(struct mapped_device *md, struct dm_table *t,
+                  struct queue_limits *limits)
 {
         struct request_queue *q = md->queue;
         sector_t size;
@@ -1337,7 +1338,7 @@ static int __bind(struct mapped_device *md, struct dm_table *t)
 
         write_lock(&md->map_lock);
         md->map = t;
-        dm_table_set_restrictions(t, q);
+        dm_table_set_restrictions(t, q, limits);
         write_unlock(&md->map_lock);
 
         return 0;
@@ -1562,6 +1563,7 @@ static void dm_queue_flush(struct mapped_device *md)
  */
 int dm_swap_table(struct mapped_device *md, struct dm_table *table)
 {
+        struct queue_limits limits;
         int r = -EINVAL;
 
         mutex_lock(&md->suspend_lock);
@@ -1570,8 +1572,12 @@ int dm_swap_table(struct mapped_device *md, struct dm_table *table)
         if (!dm_suspended(md))
                 goto out;
 
+        r = dm_calculate_queue_limits(table, &limits);
+        if (r)
+                goto out;
+
         __unbind(md);
-        r = __bind(md, table);
+        r = __bind(md, table, &limits);
 
 out:
         mutex_unlock(&md->suspend_lock);