From: Joe Thornber Change existing users of the function dm_cell_release_singleton to share cell_defer_except instead, and then remove the now-unused function. Everywhere that calls dm_cell_release_singleton, the bio in question is the holder of the cell. If there are no non-holder entries in the cell then cell_defer_except behaves exactly like dm_cell_release_singleton. Conversely, if there *are* non-holder entries then dm_cell_release_singleton must not be used because those entries would need to be deferred. Consequently, it is safe to replace use of dm_cell_release_singleton with cell_defer_except. This patch is a pre-requisite for "dm thin: fix race between simultaneous io and discards to same block". Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org Signed-off-by: Alasdair G Kergon --- drivers/md/dm-bio-prison.c | 25 ------------------------- drivers/md/dm-bio-prison.h | 1 - drivers/md/dm-thin.c | 25 ++++++++++++------------- 3 files changed, 12 insertions(+), 39 deletions(-) Index: linux/drivers/md/dm-bio-prison.c =================================================================== --- linux.orig/drivers/md/dm-bio-prison.c +++ linux/drivers/md/dm-bio-prison.c @@ -208,31 +208,6 @@ void dm_cell_release(struct dm_bio_priso EXPORT_SYMBOL_GPL(dm_cell_release); /* - * There are a couple of places where we put a bio into a cell briefly - * before taking it out again. In these situations we know that no other - * bio may be in the cell. This function releases the cell, and also does - * a sanity check. - */ -static void __cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio) -{ - BUG_ON(cell->holder != bio); - BUG_ON(!bio_list_empty(&cell->bios)); - - __cell_release(cell, NULL); -} - -void dm_cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio) -{ - unsigned long flags; - struct dm_bio_prison *prison = cell->prison; - - spin_lock_irqsave(&prison->lock, flags); - __cell_release_singleton(cell, bio); - spin_unlock_irqrestore(&prison->lock, flags); -} -EXPORT_SYMBOL_GPL(dm_cell_release_singleton); - -/* * Sometimes we don't want the holder, just the additional bios. */ static void __cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates) Index: linux/drivers/md/dm-bio-prison.h =================================================================== --- linux.orig/drivers/md/dm-bio-prison.h +++ linux/drivers/md/dm-bio-prison.h @@ -44,7 +44,6 @@ int dm_bio_detain(struct dm_bio_prison * struct bio *inmate, struct dm_bio_prison_cell **ref); void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios); -void dm_cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio); // FIXME: bio arg not needed void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates); void dm_cell_error(struct dm_bio_prison_cell *cell); Index: linux/drivers/md/dm-thin.c =================================================================== --- linux.orig/drivers/md/dm-thin.c +++ linux/drivers/md/dm-thin.c @@ -513,8 +513,7 @@ static void cell_defer(struct thin_c *tc } /* - * Same as cell_defer above, except it omits one particular detainee, - * a write bio that covers the block and has already been processed. + * Same as cell_defer except it omits the original holder of the cell. */ static void cell_defer_except(struct thin_c *tc, struct dm_bio_prison_cell *cell) { @@ -936,7 +935,7 @@ static void process_discard(struct thin_ */ build_data_key(tc->td, lookup_result.block, &key2); if (dm_bio_detain(tc->pool->prison, &key2, bio, &cell2)) { - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); break; } @@ -967,8 +966,8 @@ static void process_discard(struct thin_ * a block boundary. So we submit the discard of a * partial block appropriately. */ - dm_cell_release_singleton(cell, bio); - dm_cell_release_singleton(cell2, bio); + cell_defer_except(tc, cell); + cell_defer_except(tc, cell2); if ((!lookup_result.shared) && pool->pf.discard_passdown) remap_and_issue(tc, bio, lookup_result.block); else @@ -980,13 +979,13 @@ static void process_discard(struct thin_ /* * It isn't provisioned, just forget it. */ - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); bio_endio(bio, 0); break; default: DMERR("discard: find block unexpectedly returned %d", r); - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); bio_io_error(bio); break; } @@ -1041,7 +1040,7 @@ static void process_shared_bio(struct th h->shared_read_entry = dm_deferred_entry_inc(pool->shared_read_ds); - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); remap_and_issue(tc, bio, lookup_result->block); } } @@ -1056,7 +1055,7 @@ static void provision_block(struct thin_ * Remap empty bios (flushes) immediately, without provisioning. */ if (!bio->bi_size) { - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); remap_and_issue(tc, bio, 0); return; } @@ -1066,7 +1065,7 @@ static void provision_block(struct thin_ */ if (bio_data_dir(bio) == READ) { zero_fill_bio(bio); - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); bio_endio(bio, 0); return; } @@ -1120,7 +1119,7 @@ static void process_bio(struct thin_c *t * TODO: this will probably have to change when discard goes * back in. */ - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); if (lookup_result.shared) process_shared_bio(tc, bio, block, &lookup_result); @@ -1130,7 +1129,7 @@ static void process_bio(struct thin_c *t case -ENODATA: if (bio_data_dir(bio) == READ && tc->origin_dev) { - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); remap_to_origin_and_issue(tc, bio); } else provision_block(tc, bio, block, cell); @@ -1138,7 +1137,7 @@ static void process_bio(struct thin_c *t default: DMERR("dm_thin_find_block() failed, error = %d", r); - dm_cell_release_singleton(cell, bio); + cell_defer_except(tc, cell); bio_io_error(bio); break; }