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authorChristoph Hellwig <hch@infradead.org>2011-10-18 06:57:03 -0400
committerNicholas Bellinger <nab@linux-iscsi.org>2011-10-24 03:22:04 +0000
commitaf3f00c75949369d937f499f49118e879939724d (patch)
tree97be6b877cd80489eb055ccf1dd0bdb5e8c3f526
parent9ac549873d35626cd6d7718691aaf4c55f2667a7 (diff)
target: re-use the command S/G list for single-task commands
If we only have a single task per command (which at least in my testing is the by far most common case) we do not have to allocate a new per-task S/G list but can reuse the one from the command. (nab: Fix BIDI handling in transport_free_dev_tasks) Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
-rw-r--r--drivers/target/target_core_transport.c42
1 files changed, 31 insertions, 11 deletions
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index ab4e3083d96..ac048db2124 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -3551,7 +3551,9 @@ static void transport_free_dev_tasks(struct se_cmd *cmd)
*/
del_timer_sync(&task->task_timer);
- kfree(task->task_sg);
+ if (task->task_sg != cmd->t_data_sg &&
+ task->task_sg != cmd->t_bidi_data_sg)
+ kfree(task->task_sg);
list_del(&task->t_list);
@@ -3830,7 +3832,33 @@ transport_allocate_data_tasks(struct se_cmd *cmd,
lba = cmd->t_task_lba;
sectors = DIV_ROUND_UP(cmd->data_length, sector_size);
task_count = DIV_ROUND_UP_SECTOR_T(sectors, dev_max_sectors);
-
+
+ /*
+ * If we need just a single task reuse the SG list in the command
+ * and avoid a lot of work.
+ */
+ if (task_count == 1) {
+ struct se_task *task;
+ unsigned long flags;
+
+ task = transport_generic_get_task(cmd, data_direction);
+ if (!task)
+ return -ENOMEM;
+
+ task->task_sg = cmd_sg;
+ task->task_sg_nents = sgl_nents;
+
+ task->task_lba = lba;
+ task->task_sectors = sectors;
+ task->task_size = task->task_sectors * sector_size;
+
+ spin_lock_irqsave(&cmd->t_state_lock, flags);
+ list_add_tail(&task->t_list, &cmd->t_task_list);
+ spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+
+ return task_count;
+ }
+
for (i = 0; i < task_count; i++) {
struct se_task *task;
unsigned int task_size, task_sg_nents_padded;
@@ -3906,15 +3934,7 @@ transport_allocate_control_task(struct se_cmd *cmd)
if (!task)
return -ENOMEM;
- task->task_sg = kmalloc(sizeof(struct scatterlist) * cmd->t_data_nents,
- GFP_KERNEL);
- if (!task->task_sg) {
- cmd->se_dev->transport->free_task(task);
- return -ENOMEM;
- }
-
- memcpy(task->task_sg, cmd->t_data_sg,
- sizeof(struct scatterlist) * cmd->t_data_nents);
+ task->task_sg = cmd->t_data_sg;
task->task_size = cmd->data_length;
task->task_sg_nents = cmd->t_data_nents;