block: support different tag allocation policy
The libata tag allocation is using a round-robin policy. Next patch will
make libata use block generic tag allocation, so let's add a policy to
tag allocation.
Currently two policies: FIFO (default) and round-robin.
Cc: Jens Axboe <axboe@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 019e668..e113c75 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -402,6 +402,9 @@
*/
unsigned char present;
+ /* If use block layer to manage tags, this is tag allocation policy */
+ int tag_alloc_policy;
+
/*
* Let the block layer assigns tags to all commands.
*/