block: introduce rq_list_for_each_safe macro

While iterating a list, a particular request may need to be removed for
special handling. Provide an iterator that can safely handle that.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20220105170518.3181469-3-kbusch@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index bf64b94..1467f0f 100644 (file)
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -242,6 +242,10 @@ static inline unsigned short req_get_ioprio(struct request *req)
 #define rq_list_for_each(listptr, pos)                 \
        for (pos = rq_list_peek((listptr)); pos; pos = rq_list_next(pos))
 
+#define rq_list_for_each_safe(listptr, pos, nxt)                       \
+       for (pos = rq_list_peek((listptr)), nxt = rq_list_next(pos);    \
+               pos; pos = nxt, nxt = pos ? rq_list_next(pos) : NULL)
+
 #define rq_list_next(rq)       (rq)->rq_next
 #define rq_list_empty(list)    ((list) == (struct request *) NULL)