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-rw-r--r--block/blk-mq.h32
1 files changed, 32 insertions, 0 deletions
diff --git a/block/blk-mq.h b/block/blk-mq.h
index f4bf5161333e..32c62c64e6c2 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -233,4 +233,36 @@ static inline void blk_mq_clear_mq_map(struct blk_mq_queue_map *qmap)
qmap->mq_map[cpu] = 0;
}
+/*
+ * blk_mq_plug() - Get caller context plug
+ * @q: request queue
+ * @bio : the bio being submitted by the caller context
+ *
+ * Plugging, by design, may delay the insertion of BIOs into the elevator in
+ * order to increase BIO merging opportunities. This however can cause BIO
+ * insertion order to change from the order in which submit_bio() is being
+ * executed in the case of multiple contexts concurrently issuing BIOs to a
+ * device, even if these context are synchronized to tightly control BIO issuing
+ * order. While this is not a problem with regular block devices, this ordering
+ * change can cause write BIO failures with zoned block devices as these
+ * require sequential write patterns to zones. Prevent this from happening by
+ * ignoring the plug state of a BIO issuing context if the target request queue
+ * is for a zoned block device and the BIO to plug is a write operation.
+ *
+ * Return current->plug if the bio can be plugged and NULL otherwise
+ */
+static inline struct blk_plug *blk_mq_plug(struct request_queue *q,
+ struct bio *bio)
+{
+ /*
+ * For regular block devices or read operations, use the context plug
+ * which may be NULL if blk_start_plug() was not executed.
+ */
+ if (!blk_queue_is_zoned(q) || !op_is_write(bio_op(bio)))
+ return current->plug;
+
+ /* Zoned block device write operation case: do not plug the BIO */
+ return NULL;
+}
+
#endif