Commit 3f8d3f54 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm bio prison v1: add dm_cell_key_has_valid_range 



Don't have bio_detain() BUG_ON if a dm_cell_key is beyond
BIO_PRISON_MAX_RANGE or spans a boundary.

Update dm-thin.c:build_key() to use dm_cell_key_has_valid_range() which
will do this checking without using BUG_ON. Also update
process_discard_bio() to check the discard bio that DM core passes in
(having first imposed max_discard_granularity based splitting).

dm_cell_key_has_valid_range() will merely WARN_ON_ONCE if it returns
false because if it does: it is programmer error that should be caught
with proper testing. So relax the BUG_ONs to be WARN_ON_ONCE.

Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent e2dd8aca

drivers/md/dm-bio-prison-v1.c

+9 −5
Original line number Diff line number Diff line
@@ -120,12 +120,17 @@ static unsigned lock_nr(struct dm_cell_key *key) 
	return (key->block_begin >> BIO_PRISON_MAX_RANGE_SHIFT) & LOCK_MASK;

}



static void check_range(struct dm_cell_key *key)

bool dm_cell_key_has_valid_range(struct dm_cell_key *key)

{

	BUG_ON(key->block_end - key->block_begin > BIO_PRISON_MAX_RANGE);

	BUG_ON((key->block_begin >> BIO_PRISON_MAX_RANGE_SHIFT) !=

	       ((key->block_end - 1) >> BIO_PRISON_MAX_RANGE_SHIFT));

	if (WARN_ON_ONCE(key->block_end - key->block_begin > BIO_PRISON_MAX_RANGE))

		return false;

	if (WARN_ON_ONCE((key->block_begin >> BIO_PRISON_MAX_RANGE_SHIFT) !=

			 (key->block_end - 1) >> BIO_PRISON_MAX_RANGE_SHIFT))

		return false;



	return true;

}

EXPORT_SYMBOL(dm_cell_key_has_valid_range);



static int __bio_detain(struct rb_root *root,

			struct dm_cell_key *key,
@@ -172,7 +177,6 @@ static int bio_detain(struct dm_bio_prison *prison, 
{

	int r;

	unsigned l = lock_nr(key);

	check_range(key);



	spin_lock_irq(&prison->regions[l].lock);

	r = __bio_detain(&prison->regions[l].cell, key, inmate, cell_prealloc, cell_result);

drivers/md/dm-bio-prison-v1.h

+5 −0
Original line number Diff line number Diff line
@@ -83,6 +83,11 @@ int dm_get_cell(struct dm_bio_prison *prison, 
		struct dm_bio_prison_cell *cell_prealloc,

		struct dm_bio_prison_cell **cell_result);



/*

 * Returns false if key is beyond BIO_PRISON_MAX_RANGE or spans a boundary.

 */

bool dm_cell_key_has_valid_range(struct dm_cell_key *key);



/*

 * An atomic op that combines retrieving or creating a cell, and adding a

 * bio to it.

drivers/md/dm-thin.c

+15 −6
Original line number Diff line number Diff line
@@ -118,25 +118,27 @@ enum lock_space { 
	PHYSICAL

};



static void build_key(struct dm_thin_device *td, enum lock_space ls,

static bool build_key(struct dm_thin_device *td, enum lock_space ls,

		      dm_block_t b, dm_block_t e, struct dm_cell_key *key)

{

	key->virtual = (ls == VIRTUAL);

	key->dev = dm_thin_dev_id(td);

	key->block_begin = b;

	key->block_end = e;



	return dm_cell_key_has_valid_range(key);

}



static void build_data_key(struct dm_thin_device *td, dm_block_t b,

			   struct dm_cell_key *key)

{

	build_key(td, PHYSICAL, b, b + 1llu, key);

	(void) build_key(td, PHYSICAL, b, b + 1llu, key);

}



static void build_virtual_key(struct dm_thin_device *td, dm_block_t b,

			      struct dm_cell_key *key)

{

	build_key(td, VIRTUAL, b, b + 1llu, key);

	(void) build_key(td, VIRTUAL, b, b + 1llu, key);

}



/*----------------------------------------------------------------*/
@@ -1702,7 +1704,8 @@ static void break_up_discard_bio(struct thin_c *tc, dm_block_t begin, dm_block_t 
				<< BIO_PRISON_MAX_RANGE_SHIFT;

			len = min_t(sector_t, data_end - data_begin, next_boundary - data_begin);



			build_key(tc->td, PHYSICAL, data_begin, data_begin + len, &data_key);

			/* This key is certainly within range given the above splitting */

			(void) build_key(tc->td, PHYSICAL, data_begin, data_begin + len, &data_key);

			if (bio_detain(tc->pool, &data_key, NULL, &data_cell)) {

				/* contention, we'll give up with this range */

				data_begin += len;
@@ -1778,8 +1781,13 @@ static void process_discard_bio(struct thin_c *tc, struct bio *bio) 
		return;

	}



	build_key(tc->td, VIRTUAL, begin, end, &virt_key);

	if (bio_detain(tc->pool, &virt_key, bio, &virt_cell))

	if (unlikely(!build_key(tc->td, VIRTUAL, begin, end, &virt_key))) {

		DMERR_LIMIT("Discard doesn't respect bio prison limits");

		bio_endio(bio);

		return;

	}



	if (bio_detain(tc->pool, &virt_key, bio, &virt_cell)) {

		/*

		 * Potential starvation issue: We're relying on the

		 * fs/application being well behaved, and not trying to
@@ -1788,6 +1796,7 @@ static void process_discard_bio(struct thin_c *tc, struct bio *bio) 
		 * cell will never be granted.

		 */

		return;

	}



	tc->pool->process_discard_cell(tc, virt_cell);

}