Commit e6fc9f62 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm: flag clones created by __send_duplicate_bios 



Formally disallow dm_accept_partial_bio() on clones created by
__send_duplicate_bios() because their len_ptr points to a shared
unsigned int.  __send_duplicate_bios() is only used for flush bios
and other "abnormal" bios (discards, writezeroes, etc). And
dm_accept_partial_bio() already didn't support flush bios.

Also refactor __send_changing_extent_only() to reflect it cannot fail.
As such __send_changing_extent_only() can update the clone_info before
__send_duplicate_bios() is called to fan-out __map_bio() calls.

Reviewed-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 300432f5

drivers/md/dm-core.h

+2 −1
Original line number Diff line number Diff line
@@ -215,7 +215,8 @@ struct dm_target_io { 
	struct dm_io *io;

	struct dm_target *ti;

	unsigned int *len_ptr;

	bool inside_dm_io;

	bool inside_dm_io:1;

	bool is_duplicate_bio:1;

	sector_t old_sector;

	struct bio clone;

};

drivers/md/dm.c

+28 −20
Original line number Diff line number Diff line
@@ -586,6 +586,7 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti, 
	tio->io = ci->io;

	tio->ti = ti;

	tio->target_bio_nr = target_bio_nr;

	tio->is_duplicate_bio = false;

	tio->len_ptr = len;

	tio->old_sector = 0;
@@ -1087,7 +1088,8 @@ static int dm_dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff, 
/*

 * A target may call dm_accept_partial_bio only from the map routine.  It is

 * allowed for all bio types except REQ_PREFLUSH, REQ_OP_ZONE_* zone management

 * operations and REQ_OP_ZONE_APPEND (zone append writes).

 * operations, REQ_OP_ZONE_APPEND (zone append writes) and any bio serviced by

 * __send_duplicate_bios().

 *

 * dm_accept_partial_bio informs the dm that the target only wants to process

 * additional n_sectors sectors of the bio and the rest of the data should be
@@ -1118,7 +1120,7 @@ void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors) 
	struct dm_target_io *tio = clone_to_tio(bio);

	unsigned bi_size = bio->bi_iter.bi_size >> SECTOR_SHIFT;



	BUG_ON(bio->bi_opf & REQ_PREFLUSH);

	BUG_ON(tio->is_duplicate_bio);

	BUG_ON(op_is_zone_mgmt(bio_op(bio)));

	BUG_ON(bio_op(bio) == REQ_OP_ZONE_APPEND);

	BUG_ON(bi_size > *tio->len_ptr);
@@ -1246,12 +1248,15 @@ static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti, 
		break;

	case 1:

		clone = alloc_tio(ci, ti, 0, len, GFP_NOIO);

		clone_to_tio(clone)->is_duplicate_bio = true;

		__map_bio(clone);

		break;

	default:

		alloc_multiple_bios(&blist, ci, ti, num_bios, len);

		while ((clone = bio_list_pop(&blist)))

		while ((clone = bio_list_pop(&blist))) {

			clone_to_tio(clone)->is_duplicate_bio = true;

			__map_bio(clone);

		}

		break;

	}

}
@@ -1280,29 +1285,22 @@ static int __send_empty_flush(struct clone_info *ci) 
	return 0;

}



static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,

static void __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,

					unsigned num_bios)

{

	unsigned len;



	/*

	 * Even though the device advertised support for this type of

	 * request, that does not mean every target supports it, and

	 * reconfiguration might also have changed that since the

	 * check was performed.

	 */

	if (!num_bios)

		return -EOPNOTSUPP;



	len = min_t(sector_t, ci->sector_count,

		    max_io_len_target_boundary(ti, dm_target_offset(ti, ci->sector)));



	__send_duplicate_bios(ci, ti, num_bios, &len);



	/*

	 * dm_accept_partial_bio cannot be used with duplicate bios,

	 * so update clone_info cursor before __send_duplicate_bios().

	 */

	ci->sector += len;

	ci->sector_count -= len;



	return 0;

	__send_duplicate_bios(ci, ti, num_bios, &len);

}



static bool is_abnormal_io(struct bio *bio)
@@ -1324,10 +1322,9 @@ static bool is_abnormal_io(struct bio *bio) 
static bool __process_abnormal_io(struct clone_info *ci, struct dm_target *ti,

				  int *result)

{

	struct bio *bio = ci->bio;

	unsigned num_bios = 0;



	switch (bio_op(bio)) {

	switch (bio_op(ci->bio)) {

	case REQ_OP_DISCARD:

		num_bios = ti->num_discard_bios;

		break;
@@ -1344,7 +1341,18 @@ static bool __process_abnormal_io(struct clone_info *ci, struct dm_target *ti, 
		return false;

	}



	*result = __send_changing_extent_only(ci, ti, num_bios);

	/*

	 * Even though the device advertised support for this type of

	 * request, that does not mean every target supports it, and

	 * reconfiguration might also have changed that since the

	 * check was performed.

	 */

	if (!num_bios)

		*result = -EOPNOTSUPP;

	else {

		__send_changing_extent_only(ci, ti, num_bios);

		*result = 0;

	}

	return true;

}