block: split out a new blk_plug.h header

blkdev.h gets included in various places outside the block layer just
for struct blk_plug and related plugging functions.

Split blk_plug into a separate helper to reduce the amount of code
that needs to get rebuilt when blkdev.h changes and to slightly
reduce compile times.

In io_uring this requires pulling in a few other headers explicitly that
previously were implicitly included through blkdev.h.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner (Amutable) <brauner@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://patch.msgid.link/20260804125524.740996-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1 insertions, 85 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9213a5716f95..20cb8ed7d987 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -7,6 +7,7 @@
 
 #include <linux/types.h>
 #include <linux/blk_types.h>
+#include <linux/blk_plug.h>
 #include <linux/device.h>
 #include <linux/list.h>
 #include <linux/llist.h>
@@ -21,7 +22,6 @@
 #include <linux/rcupdate.h>
 #include <linux/percpu-refcount.h>
 #include <linux/blkzoned.h>
-#include <linux/sched.h>
 #include <linux/sbitmap.h>
 #include <linux/uuid.h>
 #include <linux/xarray.h>
@@ -1169,94 +1169,10 @@ extern void blk_put_queue(struct request_queue *);
 
 void blk_mark_disk_dead(struct gendisk *disk);
 
-struct rq_list {
-	struct request *head;
-	struct request *tail;
-};
-
 #ifdef CONFIG_BLOCK
-/*
- * blk_plug permits building a queue of related requests by holding the I/O
- * fragments for a short period. This allows merging of sequential requests
- * into single larger request. As the requests are moved from a per-task list to
- * the device's request_queue in a batch, this results in improved scalability
- * as the lock contention for request_queue lock is reduced.
- *
- * It is ok not to disable preemption when adding the request to the plug list
- * or when attempting a merge. For details, please see schedule() where
- * blk_flush_plug() is called.
- */
-struct blk_plug {
-	struct rq_list mq_list; /* blk-mq requests */
-
-	/* if ios_left is > 1, we can batch tag/rq allocations */
-	struct rq_list cached_rqs;
-	u64 cur_ktime;
-	unsigned short nr_ios;
-
-	unsigned short rq_count;
-
-	bool multiple_queues;
-	bool has_elevator;
-
-	struct list_head cb_list; /* md requires an unplug callback */
-};
-
-struct blk_plug_cb;
-typedef void (*blk_plug_cb_fn)(struct blk_plug_cb *, bool);
-struct blk_plug_cb {
-	struct list_head list;
-	blk_plug_cb_fn callback;
-	void *data;
-};
-extern struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug,
-					     void *data, int size);
-extern void blk_start_plug(struct blk_plug *);
-extern void blk_start_plug_nr_ios(struct blk_plug *, unsigned short);
-extern void blk_finish_plug(struct blk_plug *);
-
-void __blk_flush_plug(struct blk_plug *plug, bool from_schedule);
-static inline void blk_flush_plug(struct blk_plug *plug, bool async)
-{
-	if (plug)
-		__blk_flush_plug(plug, async);
-}
-
-static __always_inline void blk_plug_invalidate_ts(void)
-{
-	if (unlikely(current->flags & PF_BLOCK_TS)) {
-		current->plug->cur_ktime = 0;
-		current->flags &= ~PF_BLOCK_TS;
-	}
-}
-
 int blkdev_issue_flush(struct block_device *bdev);
 long nr_blockdev_pages(void);
 #else /* CONFIG_BLOCK */
-struct blk_plug {
-};
-
-static inline void blk_start_plug_nr_ios(struct blk_plug *plug,
-					 unsigned short nr_ios)
-{
-}
-
-static inline void blk_start_plug(struct blk_plug *plug)
-{
-}
-
-static inline void blk_finish_plug(struct blk_plug *plug)
-{
-}
-
-static inline void blk_flush_plug(struct blk_plug *plug, bool async)
-{
-}
-
-static inline void blk_plug_invalidate_ts(void)
-{
-}
-
 static inline int blkdev_issue_flush(struct block_device *bdev)
 {
 	return 0;