From 025b96853fe0bdc977d88b4242ca5e1f19d9bb66 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Fri, 1 Mar 2013 22:45:50 +0000 Subject: [PATCH] dm thin: remove cells from stack This patch takes advantage of the new bio-prison interface where the memory is now passed in rather than using a mempool in bio-prison. This allows the map function to avoid performing potentially-blocking allocations that could lead to deadlocks: We want to avoid the cell allocation that is done in bio_detain. (The potential for mempool deadlocks still remains in other functions that use bio_detain.) Signed-off-by: Joe Thornber Signed-off-by: Alasdair G Kergon --- drivers/md/dm-bio-prison.c | 7 ------ drivers/md/dm-bio-prison.h | 12 +++++++++- drivers/md/dm-thin.c | 47 ++++++++++++++++++++++++++------------ 3 files changed, 43 insertions(+), 23 deletions(-) diff --git a/drivers/md/dm-bio-prison.c b/drivers/md/dm-bio-prison.c index ca5771d3ffd7..144067c95aba 100644 --- a/drivers/md/dm-bio-prison.c +++ b/drivers/md/dm-bio-prison.c @@ -14,13 +14,6 @@ /*----------------------------------------------------------------*/ -struct dm_bio_prison_cell { - struct hlist_node list; - struct dm_cell_key key; - struct bio *holder; - struct bio_list bios; -}; - struct dm_bio_prison { spinlock_t lock; mempool_t *cell_pool; diff --git a/drivers/md/dm-bio-prison.h b/drivers/md/dm-bio-prison.h index 11af2182101b..981a02d3a055 100644 --- a/drivers/md/dm-bio-prison.h +++ b/drivers/md/dm-bio-prison.h @@ -22,7 +22,6 @@ * subsequently unlocked the bios become available. */ struct dm_bio_prison; -struct dm_bio_prison_cell; /* FIXME: this needs to be more abstract */ struct dm_cell_key { @@ -31,6 +30,17 @@ struct dm_cell_key { dm_block_t block; }; +/* + * Treat this as opaque, only in header so callers can manage allocation + * themselves. + */ +struct dm_bio_prison_cell { + struct hlist_node list; + struct dm_cell_key key; + struct bio *holder; + struct bio_list bios; +}; + struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells); void dm_bio_prison_destroy(struct dm_bio_prison *prison); diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 5304e3a29a14..009339d62828 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -229,6 +229,17 @@ struct thin_c { /*----------------------------------------------------------------*/ +/* + * wake_worker() is used when new work is queued and when pool_resume is + * ready to continue deferred IO processing. + */ +static void wake_worker(struct pool *pool) +{ + queue_work(pool->wq, &pool->worker); +} + +/*----------------------------------------------------------------*/ + static int bio_detain(struct pool *pool, struct dm_cell_key *key, struct bio *bio, struct dm_bio_prison_cell **cell_result) { @@ -268,6 +279,19 @@ static void cell_release_no_holder(struct pool *pool, dm_bio_prison_free_cell(pool->prison, cell); } +static void cell_defer_no_holder_no_free(struct thin_c *tc, + struct dm_bio_prison_cell *cell) +{ + struct pool *pool = tc->pool; + unsigned long flags; + + spin_lock_irqsave(&pool->lock, flags); + dm_cell_release_no_holder(pool->prison, cell, &pool->deferred_bios); + spin_unlock_irqrestore(&pool->lock, flags); + + wake_worker(pool); +} + static void cell_error(struct pool *pool, struct dm_bio_prison_cell *cell) { @@ -477,15 +501,6 @@ static void remap_and_issue(struct thin_c *tc, struct bio *bio, issue(tc, bio); } -/* - * wake_worker() is used when new work is queued and when pool_resume is - * ready to continue deferred IO processing. - */ -static void wake_worker(struct pool *pool) -{ - queue_work(pool->wq, &pool->worker); -} - /*----------------------------------------------------------------*/ /* @@ -601,6 +616,7 @@ static void process_prepared_mapping_fail(struct dm_thin_new_mapping *m) list_del(&m->list); mempool_free(m, m->tc->pool->mapping_pool); } + static void process_prepared_mapping(struct dm_thin_new_mapping *m) { struct thin_c *tc = m->tc; @@ -1438,7 +1454,8 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) dm_block_t block = get_bio_block(tc, bio); struct dm_thin_device *td = tc->td; struct dm_thin_lookup_result result; - struct dm_bio_prison_cell *cell1, *cell2; + struct dm_bio_prison_cell cell1, cell2; + struct dm_bio_prison_cell *cell_result; struct dm_cell_key key; thin_hook_bio(tc, bio); @@ -1480,18 +1497,18 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) } build_virtual_key(tc->td, block, &key); - if (bio_detain(tc->pool, &key, bio, &cell1)) + if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result)) return DM_MAPIO_SUBMITTED; build_data_key(tc->td, result.block, &key); - if (bio_detain(tc->pool, &key, bio, &cell2)) { - cell_defer_no_holder(tc, cell1); + if (dm_bio_detain(tc->pool->prison, &key, bio, &cell2, &cell_result)) { + cell_defer_no_holder_no_free(tc, &cell1); return DM_MAPIO_SUBMITTED; } inc_all_io_entry(tc->pool, bio); - cell_defer_no_holder(tc, cell2); - cell_defer_no_holder(tc, cell1); + cell_defer_no_holder_no_free(tc, &cell2); + cell_defer_no_holder_no_free(tc, &cell1); remap(tc, bio, result.block); return DM_MAPIO_REMAPPED; -- 2.34.1