block: move blk_io_schedule() out of header file

blk_io_schedule() isn't called from performance sensitive code path, and
it is easier to maintain by exporting it as symbol.

Also blk_io_schedule() is only called by CONFIG_BLOCK code, so it is safe
to do this way. Meantime fixes build failure when CONFIG_BLOCK is off.

Cc: Christoph Hellwig <hch@infradead.org>
Fixes: e6249cdd ("block: add blk_io_schedule() for avoiding task hung in sync dio")
Reported-by: Satya Tangirala <satyat@google.com>
Tested-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -38,6 +38,7 @@
 #include <linux/debugfs.h>
 #include <linux/bpf.h>
 #include <linux/psi.h>
+#include <linux/sched/sysctl.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/block.h>
@@ -1812,6 +1813,18 @@ void blk_finish_plug(struct blk_plug *plug)
 }
 EXPORT_SYMBOL(blk_finish_plug);
 
+void blk_io_schedule(void)
+{
+	/* Prevent hang_check timer from firing at us during very long I/O */
+	unsigned long timeout = sysctl_hung_task_timeout_secs * HZ / 2;
+
+	if (timeout)
+		io_schedule_timeout(timeout);
+	else
+		io_schedule();
+}
+EXPORT_SYMBOL_GPL(blk_io_schedule);
+
 int __init blk_dev_init(void)
 {
 	BUILD_BUG_ON(REQ_OP_LAST >= (1 << REQ_OP_BITS));

include/linux/blkdev.h

@@ -27,7 +27,6 @@
 #include <linux/percpu-refcount.h>
 #include <linux/scatterlist.h>
 #include <linux/blkzoned.h>
-#include <linux/sched/sysctl.h>
 
 struct module;
 struct scsi_ioctl_command;
@@ -1221,6 +1220,8 @@ static inline bool blk_needs_flush_plug(struct task_struct *tsk)
 		 !list_empty(&plug->cb_list));
 }
 
+extern void blk_io_schedule(void);
+
 extern int blkdev_issue_flush(struct block_device *, gfp_t, sector_t *);
 extern int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct page *page);
@@ -1851,15 +1852,4 @@ static inline void blk_wake_io_task(struct task_struct *waiter)
 		wake_up_process(waiter);
 }
 
-static inline void blk_io_schedule(void)
-{
-	/* Prevent hang_check timer from firing at us during very long I/O */
-	unsigned long timeout = sysctl_hung_task_timeout_secs * HZ / 2;
-
-	if (timeout)
-		io_schedule_timeout(timeout);
-	else
-		io_schedule();
-}
-
 #endif