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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>
This commit is contained in:
Christoph Hellwig 2011-10-18 06:57:03 -04:00 committed by Nicholas Bellinger
parent 9ac549873d
commit af3f00c759
1 changed files with 31 additions and 11 deletions
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40
drivers/target/target_core_transport.c
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@ -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);
@ -3831,6 +3833,32 @@ transport_allocate_data_tasks(struct se_cmd *cmd,
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;