dm thin: consistently return -ENOSPC if pool has run out of data space

Commit 0a927c2f ("dm thin: return -ENOSPC when erroring retry list due
to out of data space") was a step in the right direction but didn't go
far enough.

Add a new 'out_of_data_space' flag to 'struct pool' and set it if/when
the pool runs of of data space.  This fixes cell_error() and
error_retry_list() to not blindly return -EIO.

We cannot rely on the 'error_if_no_space' feature flag since it is
transient (in that it can be reset once space is added, plus it only
controls whether errors are issued, it doesn't reflect whether the
pool is actually out of space).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-thin.c

@@ -235,6 +235,7 @@ struct pool {
 	struct pool_features pf;
 	bool low_water_triggered:1;	/* A dm event has been sent */
 	bool suspended:1;
+	bool out_of_data_space:1;
 
 	struct dm_bio_prison *prison;
 	struct dm_kcopyd_client *copier;
@@ -461,9 +462,16 @@ static void cell_error_with_code(struct pool *pool,
 	dm_bio_prison_free_cell(pool->prison, cell);
 }
 
+static int get_pool_io_error_code(struct pool *pool)
+{
+	return pool->out_of_data_space ? -ENOSPC : -EIO;
+}
+
 static void cell_error(struct pool *pool, struct dm_bio_prison_cell *cell)
 {
-	cell_error_with_code(pool, cell, -EIO);
+	int error = get_pool_io_error_code(pool);
+
+	cell_error_with_code(pool, cell, error);
 }
 
 static void cell_success(struct pool *pool, struct dm_bio_prison_cell *cell)
@@ -622,7 +630,9 @@ static void error_retry_list_with_code(struct pool *pool, int error)
 
 static void error_retry_list(struct pool *pool)
 {
-	return error_retry_list_with_code(pool, -EIO);
+	int error = get_pool_io_error_code(pool);
+
+	return error_retry_list_with_code(pool, error);
 }
 
 /*
@@ -2419,6 +2429,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
 		 */
 		if (old_mode != new_mode)
 			notify_of_pool_mode_change_to_oods(pool);
+		pool->out_of_data_space = true;
 		pool->process_bio = process_bio_read_only;
 		pool->process_discard = process_discard_bio;
 		pool->process_cell = process_cell_read_only;
@@ -2432,6 +2443,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
 	case PM_WRITE:
 		if (old_mode != new_mode)
 			notify_of_pool_mode_change(pool, "write");
+		pool->out_of_data_space = false;
 		pool->pf.error_if_no_space = pt->requested_pf.error_if_no_space;
 		dm_pool_metadata_read_write(pool->pmd);
 		pool->process_bio = process_bio;
@@ -2832,6 +2844,7 @@ static struct pool *pool_create(struct mapped_device *pool_md,
 	INIT_LIST_HEAD(&pool->active_thins);
 	pool->low_water_triggered = false;
 	pool->suspended = true;
+	pool->out_of_data_space = false;
 
 	pool->shared_read_ds = dm_deferred_set_create();
 	if (!pool->shared_read_ds) {
@@ -3886,7 +3899,7 @@ static struct target_type pool_target = {
 	.name = "thin-pool",
 	.features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
 		    DM_TARGET_IMMUTABLE,
-	.version = {1, 17, 0},
+	.version = {1, 18, 0},
 	.module = THIS_MODULE,
 	.ctr = pool_ctr,
 	.dtr = pool_dtr,
@@ -4260,7 +4273,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
 
 static struct target_type thin_target = {
 	.name = "thin",
-	.version = {1, 17, 0},
+	.version = {1, 18, 0},
 	.module	= THIS_MODULE,
 	.ctr = thin_ctr,
 	.dtr = thin_dtr,