lightnvm: refactor end_io functions for sync

To implement sync I/O support within the LightNVM core, the end_io
functions are refactored to take an end_io function pointer instead of
testing for initialized media manager, followed by calling its end_io
function.

Sync I/O can then be implemented using a callback that signal I/O
completion. This is similar to the logic found in blk_to_execute_io().
By implementing it this way, the underlying device I/Os submission logic
is abstracted away from core, targets, and media managers.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
index 2fd6871..9c9fe9c 100644
--- a/include/linux/lightnvm.h
+++ b/include/linux/lightnvm.h
@@ -148,6 +148,9 @@
 	};
 };
 
+struct nvm_rq;
+typedef void (nvm_end_io_fn)(struct nvm_rq *, int);
+
 struct nvm_rq {
 	struct nvm_tgt_instance *ins;
 	struct nvm_dev *dev;
@@ -164,6 +167,9 @@
 	void *metadata;
 	dma_addr_t dma_metadata;
 
+	struct completion *wait;
+	nvm_end_io_fn *end_io;
+
 	uint8_t opcode;
 	uint16_t nr_pages;
 	uint16_t flags;
@@ -347,7 +353,6 @@
 
 typedef blk_qc_t (nvm_tgt_make_rq_fn)(struct request_queue *, struct bio *);
 typedef sector_t (nvm_tgt_capacity_fn)(void *);
-typedef int (nvm_tgt_end_io_fn)(struct nvm_rq *, int);
 typedef void *(nvm_tgt_init_fn)(struct nvm_dev *, struct gendisk *, int, int);
 typedef void (nvm_tgt_exit_fn)(void *);
 
@@ -358,7 +363,7 @@
 	/* target entry points */
 	nvm_tgt_make_rq_fn *make_rq;
 	nvm_tgt_capacity_fn *capacity;
-	nvm_tgt_end_io_fn *end_io;
+	nvm_end_io_fn *end_io;
 
 	/* module-specific init/teardown */
 	nvm_tgt_init_fn *init;
@@ -383,7 +388,6 @@
 typedef int (nvmm_close_blk_fn)(struct nvm_dev *, struct nvm_block *);
 typedef void (nvmm_flush_blk_fn)(struct nvm_dev *, struct nvm_block *);
 typedef int (nvmm_submit_io_fn)(struct nvm_dev *, struct nvm_rq *);
-typedef int (nvmm_end_io_fn)(struct nvm_rq *, int);
 typedef int (nvmm_erase_blk_fn)(struct nvm_dev *, struct nvm_block *,
 								unsigned long);
 typedef struct nvm_lun *(nvmm_get_lun_fn)(struct nvm_dev *, int);
@@ -404,7 +408,6 @@
 	nvmm_flush_blk_fn *flush_blk;
 
 	nvmm_submit_io_fn *submit_io;
-	nvmm_end_io_fn *end_io;
 	nvmm_erase_blk_fn *erase_blk;
 
 	/* Configuration management */
@@ -434,6 +437,7 @@
 extern void nvm_free_rqd_ppalist(struct nvm_dev *, struct nvm_rq *);
 extern int nvm_erase_ppa(struct nvm_dev *, struct ppa_addr);
 extern int nvm_erase_blk(struct nvm_dev *, struct nvm_block *);
+extern void nvm_end_io(struct nvm_rq *, int);
 #else /* CONFIG_NVM */
 struct nvm_dev_ops;