From 316cc67d5e03801a5ee4ac660a4dfe9e02aed475 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Fri, 8 Jul 2011 08:19:21 +0200 Subject: [PATCH] block: document blk_plug list access I'm often confused why not disable preempt when changing blk_plug list. It would be better to add comments here in case others have the similar concerns. Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe --- include/linux/blkdev.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 92edb960124..6dcea6885a5 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -857,6 +857,12 @@ struct request_queue *blk_alloc_queue(gfp_t); struct request_queue *blk_alloc_queue_node(gfp_t, int); extern void blk_put_queue(struct request_queue *); +/* + * Note: Code in between changing the blk_plug list/cb_list or element of such + * lists is preemptable, but such code can't do sleep (or be very careful), + * otherwise data is corrupted. For details, please check schedule() where + * blk_schedule_flush_plug() is called. + */ struct blk_plug { unsigned long magic; struct list_head list; -- 2.46.0