[dm-devel] [dm-6.4 PATCH v3 15/20] dm bio prison v1: add dm_cell_key_has_valid_range

Mike Snitzer
2023-03-27T20:14:18Z

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: Mike Snitzer <snitzer@kernel.org>
---
drivers/md/dm-bio-prison-v1.c | 14 +++++++++-----
drivers/md/dm-bio-prison-v1.h | 5 +++++
drivers/md/dm-thin.c | 21 +++++++++++++++------
3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/drivers/md/dm-bio-prison-v1.c b/drivers/md/dm-bio-prison-v1.c
index 2b8af861e5f6..78bb559b521c 100644
--- a/drivers/md/dm-bio-prison-v1.c
+++ b/drivers/md/dm-bio-prison-v1.c
@@ -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);
diff --git a/drivers/md/dm-bio-prison-v1.h b/drivers/md/dm-bio-prison-v1.h
index 0b8acd6708fb..2a097ed0d85e 100644
--- a/drivers/md/dm-bio-prison-v1.h
+++ b/drivers/md/dm-bio-prison-v1.h
@@ -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.
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 33ad5695f959..2b13c949bd72 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -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);