dm thin: relax external origin size constraints

Track the size of any external origin.  Previously the external origin's
size had to be a multiple of the thin-pool's block size, that is no
longer a requirement.  In addition, snapshots that are larger than the
external origin are now supported.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 115 insertions, 43 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 4c9a3b5f4ff1..0e844a5eca8f 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -227,6 +227,7 @@ struct thin_c {
         struct list_head list;
         struct dm_dev *pool_dev;
         struct dm_dev *origin_dev;
+        sector_t origin_size;
         dm_thin_id dev_id;
 
         struct pool *pool;
@@ -590,31 +591,31 @@ static void __complete_mapping_preparation(struct dm_thin_new_mapping *m)
         }
 }
 
-static void copy_complete(int read_err, unsigned long write_err, void *context)
+static void complete_mapping_preparation(struct dm_thin_new_mapping *m)
 {
         unsigned long flags;
-        struct dm_thin_new_mapping *m = context;
         struct pool *pool = m->tc->pool;
 
-        m->err = read_err || write_err ? -EIO : 0;
-
         spin_lock_irqsave(&pool->lock, flags);
         __complete_mapping_preparation(m);
         spin_unlock_irqrestore(&pool->lock, flags);
 }
 
+static void copy_complete(int read_err, unsigned long write_err, void *context)
+{
+        struct dm_thin_new_mapping *m = context;
+
+        m->err = read_err || write_err ? -EIO : 0;
+        complete_mapping_preparation(m);
+}
+
 static void overwrite_endio(struct bio *bio, int err)
 {
-        unsigned long flags;
         struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
         struct dm_thin_new_mapping *m = h->overwrite_mapping;
-        struct pool *pool = m->tc->pool;
 
         m->err = err;
-
-        spin_lock_irqsave(&pool->lock, flags);
-        __complete_mapping_preparation(m);
-        spin_unlock_irqrestore(&pool->lock, flags);
+        complete_mapping_preparation(m);
 }
 
 /*----------------------------------------------------------------*/
@@ -824,10 +825,31 @@ static struct dm_thin_new_mapping *get_next_mapping(struct pool *pool)
         return m;
 }
 
+static void ll_zero(struct thin_c *tc, struct dm_thin_new_mapping *m,
+                    sector_t begin, sector_t end)
+{
+        int r;
+        struct dm_io_region to;
+
+        to.bdev = tc->pool_dev->bdev;
+        to.sector = begin;
+        to.count = end - begin;
+
+        r = dm_kcopyd_zero(tc->pool->copier, 1, &to, 0, copy_complete, m);
+        if (r < 0) {
+                DMERR_LIMIT("dm_kcopyd_zero() failed");
+                copy_complete(1, 1, m);
+        }
+}
+
+/*
+ * A partial copy also needs to zero the uncopied region.
+ */
 static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
                           struct dm_dev *origin, dm_block_t data_origin,
                           dm_block_t data_dest,
-                          struct dm_bio_prison_cell *cell, struct bio *bio)
+                          struct dm_bio_prison_cell *cell, struct bio *bio,
+                          sector_t len)
 {
         int r;
         struct pool *pool = tc->pool;
@@ -838,10 +860,15 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
         m->data_block = data_dest;
         m->cell = cell;
 
+        /*
+         * quiesce action + copy action + an extra reference held for the
+         * duration of this function (we may need to inc later for a
+         * partial zero).
+         */
+        atomic_set(&m->prepare_actions, 3);
+
         if (!dm_deferred_set_add_work(pool->shared_read_ds, &m->list))
-                atomic_set(&m->prepare_actions, 1); /* copy only */
-        else
-                atomic_set(&m->prepare_actions, 2); /* quiesce + copy */
+                complete_mapping_preparation(m); /* already quiesced */
 
         /*
          * IO to pool_dev remaps to the pool target's data_dev.
@@ -862,20 +889,38 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
 
                 from.bdev = origin->bdev;
                 from.sector = data_origin * pool->sectors_per_block;
-                from.count = pool->sectors_per_block;
+                from.count = len;
 
                 to.bdev = tc->pool_dev->bdev;
                 to.sector = data_dest * pool->sectors_per_block;
-                to.count = pool->sectors_per_block;
+                to.count = len;
 
                 r = dm_kcopyd_copy(pool->copier, &from, 1, &to,
                                    0, copy_complete, m);
                 if (r < 0) {
-                        mempool_free(m, pool->mapping_pool);
                         DMERR_LIMIT("dm_kcopyd_copy() failed");
-                        cell_error(pool, cell);
+                        copy_complete(1, 1, m);
+
+                        /*
+                         * We allow the zero to be issued, to simplify the
+                         * error path.  Otherwise we'd need to start
+                         * worrying about decrementing the prepare_actions
+                         * counter.
+                         */
+                }
+
+                /*
+                 * Do we need to zero a tail region?
+                 */
+                if (len < pool->sectors_per_block && pool->pf.zero_new_blocks) {
+                        atomic_inc(&m->prepare_actions);
+                        ll_zero(tc, m,
+                                data_dest * pool->sectors_per_block + len,
+                                (data_dest + 1) * pool->sectors_per_block);
                 }
         }
+
+        complete_mapping_preparation(m); /* drop our ref */
 }
 
 static void schedule_internal_copy(struct thin_c *tc, dm_block_t virt_block,
@@ -883,15 +928,8 @@ static void schedule_internal_copy(struct thin_c *tc, dm_block_t virt_block,
                                    struct dm_bio_prison_cell *cell, struct bio *bio)
 {
         schedule_copy(tc, virt_block, tc->pool_dev,
-                      data_origin, data_dest, cell, bio);
-}
-
-static void schedule_external_copy(struct thin_c *tc, dm_block_t virt_block,
-                                   dm_block_t data_dest,
-                                   struct dm_bio_prison_cell *cell, struct bio *bio)
-{
-        schedule_copy(tc, virt_block, tc->origin_dev,
-                      virt_block, data_dest, cell, bio);
+                      data_origin, data_dest, cell, bio,
+                      tc->pool->sectors_per_block);
 }
 
 static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
@@ -923,21 +961,33 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
                 save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
                 inc_all_io_entry(pool, bio);
                 remap_and_issue(tc, bio, data_block);
-        } else {
-                int r;
-                struct dm_io_region to;
 
-                to.bdev = tc->pool_dev->bdev;
-                to.sector = data_block * pool->sectors_per_block;
-                to.count = pool->sectors_per_block;
+        } else
+                ll_zero(tc, m,
+                        data_block * pool->sectors_per_block,
+                        (data_block + 1) * pool->sectors_per_block);
+}
 
-                r = dm_kcopyd_zero(pool->copier, 1, &to, 0, copy_complete, m);
-                if (r < 0) {
-                        mempool_free(m, pool->mapping_pool);
-                        DMERR_LIMIT("dm_kcopyd_zero() failed");
-                        cell_error(pool, cell);
-                }
-        }
+static void schedule_external_copy(struct thin_c *tc, dm_block_t virt_block,
+                                   dm_block_t data_dest,
+                                   struct dm_bio_prison_cell *cell, struct bio *bio)
+{
+        struct pool *pool = tc->pool;
+        sector_t virt_block_begin = virt_block * pool->sectors_per_block;
+        sector_t virt_block_end = (virt_block + 1) * pool->sectors_per_block;
+
+        if (virt_block_end <= tc->origin_size)
+                schedule_copy(tc, virt_block, tc->origin_dev,
+                              virt_block, data_dest, cell, bio,
+                              pool->sectors_per_block);
+
+        else if (virt_block_begin < tc->origin_size)
+                schedule_copy(tc, virt_block, tc->origin_dev,
+                              virt_block, data_dest, cell, bio,
+                              tc->origin_size - virt_block_begin);
+
+        else
+                schedule_zero(tc, virt_block, data_dest, cell, bio);
 }
 
 /*
@@ -1319,7 +1369,18 @@ static void process_bio(struct thin_c *tc, struct bio *bio)
                         inc_all_io_entry(pool, bio);
                         cell_defer_no_holder(tc, cell);
 
-                        remap_to_origin_and_issue(tc, bio);
+                        if (bio_end_sector(bio) <= tc->origin_size)
+                                remap_to_origin_and_issue(tc, bio);
+
+                        else if (bio->bi_iter.bi_sector < tc->origin_size) {
+                                zero_fill_bio(bio);
+                                bio->bi_iter.bi_size = (tc->origin_size - bio->bi_iter.bi_sector) << SECTOR_SHIFT;
+                                remap_to_origin_and_issue(tc, bio);
+
+                        } else {
+                                zero_fill_bio(bio);
+                                bio_endio(bio, 0);
+                        }
                 } else
                         provision_block(tc, bio, block, cell);
                 break;
@@ -3145,7 +3206,7 @@ static struct target_type pool_target = {
         .name = "thin-pool",
         .features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
                     DM_TARGET_IMMUTABLE,
-        .version = {1, 12, 0},
+        .version = {1, 13, 0},
         .module = THIS_MODULE,
         .ctr = pool_ctr,
         .dtr = pool_dtr,
@@ -3404,6 +3465,16 @@ static void thin_postsuspend(struct dm_target *ti)
         noflush_work(tc, do_noflush_stop);
 }
 
+static int thin_preresume(struct dm_target *ti)
+{
+        struct thin_c *tc = ti->private;
+
+        if (tc->origin_dev)
+                tc->origin_size = get_dev_size(tc->origin_dev->bdev);
+
+        return 0;
+}
+
 /*
  * <nr mapped sectors> <highest mapped sector>
  */
@@ -3486,12 +3557,13 @@ static int thin_iterate_devices(struct dm_target *ti,
 
 static struct target_type thin_target = {
         .name = "thin",
-        .version = {1, 12, 0},
+        .version = {1, 13, 0},
         .module = THIS_MODULE,
         .ctr = thin_ctr,
         .dtr = thin_dtr,
         .map = thin_map,
         .end_io = thin_endio,
+        .preresume = thin_preresume,
         .presuspend = thin_presuspend,
         .postsuspend = thin_postsuspend,
         .status = thin_status,