From b7ca9c9273e5eebd63880dd8a6e4e5c18fc7901d Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Fri, 21 Dec 2012 20:23:31 +0000 Subject: [PATCH] dm thin: replace dm_cell_release_singleton with cell_defer_except 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(-) diff --git a/drivers/md/dm-bio-prison.c b/drivers/md/dm-bio-prison.c index e4e841567459..aefb78e3cbf9 100644 --- a/drivers/md/dm-bio-prison.c +++ b/drivers/md/dm-bio-prison.c @@ -207,31 +207,6 @@ void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios) } 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. */ diff --git a/drivers/md/dm-bio-prison.h b/drivers/md/dm-bio-prison.h index 4e0ac376700a..53d1a7a84e2f 100644 --- a/drivers/md/dm-bio-prison.h +++ b/drivers/md/dm-bio-prison.h @@ -44,7 +44,6 @@ int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key, 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); diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 058acf3a5ba7..25dfd2311a61 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -513,8 +513,7 @@ static void cell_defer(struct thin_c *tc, struct dm_bio_prison_cell *cell, } /* - * 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_c *tc, struct bio *bio) */ 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_c *tc, struct bio *bio) * 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_c *tc, struct bio *bio) /* * 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 thin_c *tc, struct bio *bio, 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_c *tc, struct bio *bio, dm_block_t block * 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_c *tc, struct bio *bio, dm_block_t block */ 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 *tc, struct bio *bio) * 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 *tc, struct bio *bio) 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 *tc, struct bio *bio) 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; } -- 2.20.1