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authorBart Van Assche <bvanassche@acm.org>2014-10-30 14:45:11 +0100
committerChristoph Hellwig <hch@lst.de>2014-11-12 11:16:09 +0100
commit205fb5f5ba1d8edcf18009998ed05b80b7d186af (patch)
tree4f703687be0330fae7e7789f0a4534973535fd0a /block/blk-mq-tag.c
parentf1569ff1d5ae0ca8598956be632947a88f540e2a (diff)
downloadkernel-205fb5f5ba1d8edcf18009998ed05b80b7d186af.tar.gz
blk-mq: add blk_mq_unique_tag()
The queuecommand() callback functions in SCSI low-level drivers need to know which hardware context has been selected by the block layer. Since this information is not available in the request structure, and since passing the hctx pointer directly to the queuecommand callback function would require modification of all SCSI LLDs, add a function to the block layer that allows to query the hardware context index. Signed-off-by: Bart Van Assche <bvanassche@acm.org> Acked-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Sagi Grimberg <sagig@mellanox.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'block/blk-mq-tag.c')
-rw-r--r--block/blk-mq-tag.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 8317175a3009..728b9a4d5f56 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -584,6 +584,34 @@ int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
return 0;
}
+/**
+ * blk_mq_unique_tag() - return a tag that is unique queue-wide
+ * @rq: request for which to compute a unique tag
+ *
+ * The tag field in struct request is unique per hardware queue but not over
+ * all hardware queues. Hence this function that returns a tag with the
+ * hardware context index in the upper bits and the per hardware queue tag in
+ * the lower bits.
+ *
+ * Note: When called for a request that is queued on a non-multiqueue request
+ * queue, the hardware context index is set to zero.
+ */
+u32 blk_mq_unique_tag(struct request *rq)
+{
+ struct request_queue *q = rq->q;
+ struct blk_mq_hw_ctx *hctx;
+ int hwq = 0;
+
+ if (q->mq_ops) {
+ hctx = q->mq_ops->map_queue(q, rq->mq_ctx->cpu);
+ hwq = hctx->queue_num;
+ }
+
+ return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
+ (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
+}
+EXPORT_SYMBOL(blk_mq_unique_tag);
+
ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
{
char *orig_page = page;