dm bio prison: pass cell memory in

Change the dm_bio_prison interface so that instead of allocating memory
internally, dm_bio_detain is supplied with a pre-allocated cell each
time it is called.

This enables a subsequent patch to move the allocation of the struct
dm_bio_prison_cell outside the thin target's mapping function so it can
no longer block there.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 77 insertions, 26 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 35d9d0396cc2..5304e3a29a14 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -229,6 +229,54 @@ struct thin_c {
 
 /*----------------------------------------------------------------*/
 
+static int bio_detain(struct pool *pool, struct dm_cell_key *key, struct bio *bio,
+                      struct dm_bio_prison_cell **cell_result)
+{
+        int r;
+        struct dm_bio_prison_cell *cell_prealloc;
+
+        /*
+         * Allocate a cell from the prison's mempool.
+         * This might block but it can't fail.
+         */
+        cell_prealloc = dm_bio_prison_alloc_cell(pool->prison, GFP_NOIO);
+
+        r = dm_bio_detain(pool->prison, key, bio, cell_prealloc, cell_result);
+        if (r)
+                /*
+                 * We reused an old cell; we can get rid of
+                 * the new one.
+                 */
+                dm_bio_prison_free_cell(pool->prison, cell_prealloc);
+
+        return r;
+}
+
+static void cell_release(struct pool *pool,
+                         struct dm_bio_prison_cell *cell,
+                         struct bio_list *bios)
+{
+        dm_cell_release(pool->prison, cell, bios);
+        dm_bio_prison_free_cell(pool->prison, cell);
+}
+
+static void cell_release_no_holder(struct pool *pool,
+                                   struct dm_bio_prison_cell *cell,
+                                   struct bio_list *bios)
+{
+        dm_cell_release_no_holder(pool->prison, cell, bios);
+        dm_bio_prison_free_cell(pool->prison, cell);
+}
+
+static void cell_error(struct pool *pool,
+                       struct dm_bio_prison_cell *cell)
+{
+        dm_cell_error(pool->prison, cell);
+        dm_bio_prison_free_cell(pool->prison, cell);
+}
+
+/*----------------------------------------------------------------*/
+
 /*
  * A global list of pools that uses a struct mapped_device as a key.
  */
@@ -524,14 +572,14 @@ static void cell_defer(struct thin_c *tc, struct dm_bio_prison_cell *cell)
         unsigned long flags;
 
         spin_lock_irqsave(&pool->lock, flags);
-        dm_cell_release(cell, &pool->deferred_bios);
+        cell_release(pool, cell, &pool->deferred_bios);
         spin_unlock_irqrestore(&tc->pool->lock, flags);
 
         wake_worker(pool);
 }
 
 /*
- * Same as cell_defer except it omits the original holder of the cell.
+ * Same as cell_defer above, except it omits the original holder of the cell.
  */
 static void cell_defer_no_holder(struct thin_c *tc, struct dm_bio_prison_cell *cell)
 {
@@ -539,7 +587,7 @@ static void cell_defer_no_holder(struct thin_c *tc, struct dm_bio_prison_cell *c
         unsigned long flags;
 
         spin_lock_irqsave(&pool->lock, flags);
-        dm_cell_release_no_holder(cell, &pool->deferred_bios);
+        cell_release_no_holder(pool, cell, &pool->deferred_bios);
         spin_unlock_irqrestore(&pool->lock, flags);
 
         wake_worker(pool);
@@ -549,13 +597,14 @@ static void process_prepared_mapping_fail(struct dm_thin_new_mapping *m)
 {
         if (m->bio)
                 m->bio->bi_end_io = m->saved_bi_end_io;
-        dm_cell_error(m->cell);
+        cell_error(m->tc->pool, m->cell);
         list_del(&m->list);
         mempool_free(m, m->tc->pool->mapping_pool);
 }
 static void process_prepared_mapping(struct dm_thin_new_mapping *m)
 {
         struct thin_c *tc = m->tc;
+        struct pool *pool = tc->pool;
         struct bio *bio;
         int r;
 
@@ -564,7 +613,7 @@ static void process_prepared_mapping(struct dm_thin_new_mapping *m)
                 bio->bi_end_io = m->saved_bi_end_io;
 
         if (m->err) {
-                dm_cell_error(m->cell);
+                cell_error(pool, m->cell);
                 goto out;
         }
 
@@ -576,7 +625,7 @@ static void process_prepared_mapping(struct dm_thin_new_mapping *m)
         r = dm_thin_insert_block(tc->td, m->virt_block, m->data_block);
         if (r) {
                 DMERR_LIMIT("dm_thin_insert_block() failed");
-                dm_cell_error(m->cell);
+                cell_error(pool, m->cell);
                 goto out;
         }
 
@@ -594,7 +643,7 @@ static void process_prepared_mapping(struct dm_thin_new_mapping *m)
 
 out:
         list_del(&m->list);
-        mempool_free(m, tc->pool->mapping_pool);
+        mempool_free(m, pool->mapping_pool);
 }
 
 static void process_prepared_discard_fail(struct dm_thin_new_mapping *m)
@@ -745,7 +794,7 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
                 if (r < 0) {
                         mempool_free(m, pool->mapping_pool);
                         DMERR_LIMIT("dm_kcopyd_copy() failed");
-                        dm_cell_error(cell);
+                        cell_error(pool, cell);
                 }
         }
 }
@@ -811,7 +860,7 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
                 if (r < 0) {
                         mempool_free(m, pool->mapping_pool);
                         DMERR_LIMIT("dm_kcopyd_zero() failed");
-                        dm_cell_error(cell);
+                        cell_error(pool, cell);
                 }
         }
 }
@@ -917,13 +966,13 @@ static void retry_on_resume(struct bio *bio)
         spin_unlock_irqrestore(&pool->lock, flags);
 }
 
-static void no_space(struct dm_bio_prison_cell *cell)
+static void no_space(struct pool *pool, struct dm_bio_prison_cell *cell)
 {
         struct bio *bio;
         struct bio_list bios;
 
         bio_list_init(&bios);
-        dm_cell_release(cell, &bios);
+        cell_release(pool, cell, &bios);
 
         while ((bio = bio_list_pop(&bios)))
                 retry_on_resume(bio);
@@ -941,7 +990,7 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
         struct dm_thin_new_mapping *m;
 
         build_virtual_key(tc->td, block, &key);
-        if (dm_bio_detain(tc->pool->prison, &key, bio, &cell))
+        if (bio_detain(tc->pool, &key, bio, &cell))
                 return;
 
         r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
@@ -953,7 +1002,7 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
                  * on this block.
                  */
                 build_data_key(tc->td, lookup_result.block, &key2);
-                if (dm_bio_detain(tc->pool->prison, &key2, bio, &cell2)) {
+                if (bio_detain(tc->pool, &key2, bio, &cell2)) {
                         cell_defer_no_holder(tc, cell);
                         break;
                 }
@@ -1029,13 +1078,13 @@ static void break_sharing(struct thin_c *tc, struct bio *bio, dm_block_t block,
                 break;
 
         case -ENOSPC:
-                no_space(cell);
+                no_space(tc->pool, cell);
                 break;
 
         default:
                 DMERR_LIMIT("%s: alloc_data_block() failed: error = %d",
                             __func__, r);
-                dm_cell_error(cell);
+                cell_error(tc->pool, cell);
                 break;
         }
 }
@@ -1053,7 +1102,7 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
          * of being broken so we have nothing further to do here.
          */
         build_data_key(tc->td, lookup_result->block, &key);
-        if (dm_bio_detain(pool->prison, &key, bio, &cell))
+        if (bio_detain(pool, &key, bio, &cell))
                 return;
 
         if (bio_data_dir(bio) == WRITE && bio->bi_size)
@@ -1074,12 +1123,13 @@ static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block
 {
         int r;
         dm_block_t data_block;
+        struct pool *pool = tc->pool;
 
         /*
          * Remap empty bios (flushes) immediately, without provisioning.
          */
         if (!bio->bi_size) {
-                inc_all_io_entry(tc->pool, bio);
+                inc_all_io_entry(pool, bio);
                 cell_defer_no_holder(tc, cell);
 
                 remap_and_issue(tc, bio, 0);
@@ -1106,14 +1156,14 @@ static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block
                 break;
 
         case -ENOSPC:
-                no_space(cell);
+                no_space(pool, cell);
                 break;
 
         default:
                 DMERR_LIMIT("%s: alloc_data_block() failed: error = %d",
                             __func__, r);
-                set_pool_mode(tc->pool, PM_READ_ONLY);
-                dm_cell_error(cell);
+                set_pool_mode(pool, PM_READ_ONLY);
+                cell_error(pool, cell);
                 break;
         }
 }
@@ -1121,6 +1171,7 @@ static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block
 static void process_bio(struct thin_c *tc, struct bio *bio)
 {
         int r;
+        struct pool *pool = tc->pool;
         dm_block_t block = get_bio_block(tc, bio);
         struct dm_bio_prison_cell *cell;
         struct dm_cell_key key;
@@ -1131,7 +1182,7 @@ static void process_bio(struct thin_c *tc, struct bio *bio)
          * being provisioned so we have nothing further to do here.
          */
         build_virtual_key(tc->td, block, &key);
-        if (dm_bio_detain(tc->pool->prison, &key, bio, &cell))
+        if (bio_detain(pool, &key, bio, &cell))
                 return;
 
         r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
@@ -1139,9 +1190,9 @@ static void process_bio(struct thin_c *tc, struct bio *bio)
         case 0:
                 if (lookup_result.shared) {
                         process_shared_bio(tc, bio, block, &lookup_result);
-                        cell_defer_no_holder(tc, cell);
+                        cell_defer_no_holder(tc, cell); /* FIXME: pass this cell into process_shared? */
                 } else {
-                        inc_all_io_entry(tc->pool, bio);
+                        inc_all_io_entry(pool, bio);
                         cell_defer_no_holder(tc, cell);
 
                         remap_and_issue(tc, bio, lookup_result.block);
@@ -1150,7 +1201,7 @@ static void process_bio(struct thin_c *tc, struct bio *bio)
 
         case -ENODATA:
                 if (bio_data_dir(bio) == READ && tc->origin_dev) {
-                        inc_all_io_entry(tc->pool, bio);
+                        inc_all_io_entry(pool, bio);
                         cell_defer_no_holder(tc, cell);
 
                         remap_to_origin_and_issue(tc, bio);
@@ -1429,11 +1480,11 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
                 }
 
                 build_virtual_key(tc->td, block, &key);
-                if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1))
+                if (bio_detain(tc->pool, &key, bio, &cell1))
                         return DM_MAPIO_SUBMITTED;
 
                 build_data_key(tc->td, result.block, &key);
-                if (dm_bio_detain(tc->pool->prison, &key, bio, &cell2)) {
+                if (bio_detain(tc->pool, &key, bio, &cell2)) {
                         cell_defer_no_holder(tc, cell1);
                         return DM_MAPIO_SUBMITTED;
                 }