dm thin: remove cells from stack
This patch takes advantage of the new bio-prison interface where the
memory is now passed in rather than using a mempool in bio-prison.
This allows the map function to avoid performing potentially-blocking
allocations that could lead to deadlocks: We want to avoid the cell
allocation that is done in bio_detain.
(The potential for mempool deadlocks still remains in other functions
that use bio_detain.)
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 5304e3a..009339d 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -229,6 +229,17 @@
/*----------------------------------------------------------------*/
+/*
+ * wake_worker() is used when new work is queued and when pool_resume is
+ * ready to continue deferred IO processing.
+ */
+static void wake_worker(struct pool *pool)
+{
+ queue_work(pool->wq, &pool->worker);
+}
+
+/*----------------------------------------------------------------*/
+
static int bio_detain(struct pool *pool, struct dm_cell_key *key, struct bio *bio,
struct dm_bio_prison_cell **cell_result)
{
@@ -268,6 +279,19 @@
dm_bio_prison_free_cell(pool->prison, cell);
}
+static void cell_defer_no_holder_no_free(struct thin_c *tc,
+ struct dm_bio_prison_cell *cell)
+{
+ struct pool *pool = tc->pool;
+ unsigned long flags;
+
+ spin_lock_irqsave(&pool->lock, flags);
+ dm_cell_release_no_holder(pool->prison, cell, &pool->deferred_bios);
+ spin_unlock_irqrestore(&pool->lock, flags);
+
+ wake_worker(pool);
+}
+
static void cell_error(struct pool *pool,
struct dm_bio_prison_cell *cell)
{
@@ -477,15 +501,6 @@
issue(tc, bio);
}
-/*
- * wake_worker() is used when new work is queued and when pool_resume is
- * ready to continue deferred IO processing.
- */
-static void wake_worker(struct pool *pool)
-{
- queue_work(pool->wq, &pool->worker);
-}
-
/*----------------------------------------------------------------*/
/*
@@ -601,6 +616,7 @@
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;
@@ -1438,7 +1454,8 @@
dm_block_t block = get_bio_block(tc, bio);
struct dm_thin_device *td = tc->td;
struct dm_thin_lookup_result result;
- struct dm_bio_prison_cell *cell1, *cell2;
+ struct dm_bio_prison_cell cell1, cell2;
+ struct dm_bio_prison_cell *cell_result;
struct dm_cell_key key;
thin_hook_bio(tc, bio);
@@ -1480,18 +1497,18 @@
}
build_virtual_key(tc->td, block, &key);
- if (bio_detain(tc->pool, &key, bio, &cell1))
+ if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result))
return DM_MAPIO_SUBMITTED;
build_data_key(tc->td, result.block, &key);
- if (bio_detain(tc->pool, &key, bio, &cell2)) {
- cell_defer_no_holder(tc, cell1);
+ if (dm_bio_detain(tc->pool->prison, &key, bio, &cell2, &cell_result)) {
+ cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
}
inc_all_io_entry(tc->pool, bio);
- cell_defer_no_holder(tc, cell2);
- cell_defer_no_holder(tc, cell1);
+ cell_defer_no_holder_no_free(tc, &cell2);
+ cell_defer_no_holder_no_free(tc, &cell1);
remap(tc, bio, result.block);
return DM_MAPIO_REMAPPED;