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authorJoe Thornber <ejt@redhat.com>2013-03-02 02:45:50 +0400
committerAlasdair G Kergon <agk@redhat.com>2013-03-02 02:45:50 +0400
commit025b96853fe0bdc977d88b4242ca5e1f19d9bb66 (patch)
tree5bf111eac74bb2798495fd4975b0d8df72c8d351
parent6beca5eb6e801aea810da6cbc4990d96e6c1c0bc (diff)
downloadlinux-025b96853fe0bdc977d88b4242ca5e1f19d9bb66.tar.xz
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 <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
-rw-r--r--drivers/md/dm-bio-prison.c7
-rw-r--r--drivers/md/dm-bio-prison.h12
-rw-r--r--drivers/md/dm-thin.c47
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;