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Commit a2f83e8b authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm snapshot: introduce account_start_copy() and account_end_copy() 



This simple refactoring moves code for modifying the semaphore cow_count
into separate functions to prepare for changes that will extend these
methods to provide for a more sophisticated mechanism for COW
throttling.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Reviewed-by: default avatarNikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 0a005856

drivers/md/dm-snap.c

+15 −5
Original line number Diff line number Diff line
@@ -1512,6 +1512,16 @@ static void snapshot_dtr(struct dm_target *ti) 
	kfree(s);

}



static void account_start_copy(struct dm_snapshot *s)

{

	down(&s->cow_count);

}



static void account_end_copy(struct dm_snapshot *s)

{

	up(&s->cow_count);

}



/*

 * Flush a list of buffers.

 */
@@ -1732,7 +1742,7 @@ static void copy_callback(int read_err, unsigned long write_err, void *context) 
		rb_link_node(&pe->out_of_order_node, parent, p);

		rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);

	}

	up(&s->cow_count);

	account_end_copy(s);

}



/*
@@ -1756,7 +1766,7 @@ static void start_copy(struct dm_snap_pending_exception *pe) 
	dest.count = src.count;



	/* Hand over to kcopyd */

	down(&s->cow_count);

	account_start_copy(s);

	dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);

}
@@ -1776,7 +1786,7 @@ static void start_full_bio(struct dm_snap_pending_exception *pe, 
	pe->full_bio = bio;

	pe->full_bio_end_io = bio->bi_end_io;



	down(&s->cow_count);

	account_start_copy(s);

	callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,

						   copy_callback, pe);
@@ -1866,7 +1876,7 @@ static void zero_callback(int read_err, unsigned long write_err, void *context) 
	struct bio *bio = context;

	struct dm_snapshot *s = bio->bi_private;



	up(&s->cow_count);

	account_end_copy(s);

	bio->bi_status = write_err ? BLK_STS_IOERR : 0;

	bio_endio(bio);

}
@@ -1880,7 +1890,7 @@ static void zero_exception(struct dm_snapshot *s, struct dm_exception *e, 
	dest.sector = bio->bi_iter.bi_sector;

	dest.count = s->store->chunk_size;



	down(&s->cow_count);

	account_start_copy(s);

	WARN_ON_ONCE(bio->bi_private);

	bio->bi_private = s;

	dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);