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-rw-r--r--block/blk-core.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 684d7eb33d4..97e9e5405b8 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2595,6 +2595,20 @@ EXPORT_SYMBOL(kblockd_schedule_delayed_work);
#define PLUG_MAGIC 0x91827364
+/**
+ * blk_start_plug - initialize blk_plug and track it inside the task_struct
+ * @plug: The &struct blk_plug that needs to be initialized
+ *
+ * Description:
+ * 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.
+ */
void blk_start_plug(struct blk_plug *plug)
{
struct task_struct *tsk = current;