Commit 563a225c authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm: introduce dm_{get,put}_live_table_bio called from dm_submit_bio 



If a bio is marked REQ_NOWAIT optimize dm_submit_bio()'s dm_table RCU
usage to dm_{get,put}_live_table_fast.

DM core offers protection against blocking (via suspend) if REQ_NOWAIT.

Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent 982b48ae

drivers/md/dm.c

+24 −4
Original line number Diff line number Diff line
@@ -661,14 +661,16 @@ static void queue_io(struct mapped_device *md, struct bio *bio) 
 * function to access the md->map field, and make sure they call

 * dm_put_live_table() when finished.

 */

struct dm_table *dm_get_live_table(struct mapped_device *md, int *srcu_idx) __acquires(md->io_barrier)

struct dm_table *dm_get_live_table(struct mapped_device *md,

				   int *srcu_idx) __acquires(md->io_barrier)

{

	*srcu_idx = srcu_read_lock(&md->io_barrier);



	return srcu_dereference(md->map, &md->io_barrier);

}



void dm_put_live_table(struct mapped_device *md, int srcu_idx) __releases(md->io_barrier)

void dm_put_live_table(struct mapped_device *md,

		       int srcu_idx) __releases(md->io_barrier)

{

	srcu_read_unlock(&md->io_barrier, srcu_idx);

}
@@ -694,6 +696,24 @@ static void dm_put_live_table_fast(struct mapped_device *md) __releases(RCU) 
	rcu_read_unlock();

}



static inline struct dm_table *dm_get_live_table_bio(struct mapped_device *md,

						     int *srcu_idx, struct bio *bio)

{

	if (bio->bi_opf & REQ_NOWAIT)

		return dm_get_live_table_fast(md);

	else

		return dm_get_live_table(md, srcu_idx);

}



static inline void dm_put_live_table_bio(struct mapped_device *md, int srcu_idx,

					 struct bio *bio)

{

	if (bio->bi_opf & REQ_NOWAIT)

		dm_put_live_table_fast(md);

	else

		dm_put_live_table(md, srcu_idx);

}



static char *_dm_claim_ptr = "I belong to device-mapper";



/*
@@ -1612,7 +1632,7 @@ static void dm_submit_bio(struct bio *bio) 
	int srcu_idx;

	struct dm_table *map;



	map = dm_get_live_table(md, &srcu_idx);

	map = dm_get_live_table_bio(md, &srcu_idx, bio);



	/* If suspended, or map not yet available, queue this IO for later */

	if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) ||
@@ -1635,7 +1655,7 @@ static void dm_submit_bio(struct bio *bio) 


	dm_split_and_process_bio(md, map, bio);

out:

	dm_put_live_table(md, srcu_idx);

	dm_put_live_table_bio(md, srcu_idx, bio);

}



static bool dm_poll_dm_io(struct dm_io *io, struct io_comp_batch *iob,