blk_start_plug — initialize blk_plug and track it inside the task_struct
void blk_start_plug ( | struct blk_plug * plug); |
Tracking blk_plug inside the task_struct will help with auto-flushing the
pending I/O should the task end up blocking between blk_start_plug and
blk_finish_plug. This is important from a performance perspective, but
also ensures that we don't deadlock. For instance, if the task is blocking
for a memory allocation, memory reclaim could end up wanting to free a
page belonging to that request that is currently residing in our private
plug. By flushing the pending I/O when the process goes to sleep, we avoid
this kind of deadlock.