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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 03-02-2012, 10:59 PM
Mike Snitzer
 
Default dm thin: elevate the bio_prison and deferred_set code to allow for re-use

Allow other DM targets to make use of the bio_prison and deferred_set
infrastructure. Code elevated to drivers/md/dm-bio-prison.[hc]

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/Makefile | 2 +-
drivers/md/dm-bio-prison.c | 336 +++++++++++++++++++++++++++++++++++++
drivers/md/dm-bio-prison.h | 110 ++++++++++++
drivers/md/dm-thin-metadata.h | 6 +-
drivers/md/dm-thin.c | 368 +----------------------------------------
5 files changed, 449 insertions(+), 373 deletions(-)
create mode 100644 drivers/md/dm-bio-prison.c
create mode 100644 drivers/md/dm-bio-prison.h

diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 046860c..c1706ed 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -3,7 +3,7 @@
#

dm-mod-y += dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o
- dm-ioctl.o dm-io.o dm-kcopyd.o dm-sysfs.o
+ dm-ioctl.o dm-io.o dm-kcopyd.o dm-sysfs.o dm-bio-prison.o
dm-multipath-y += dm-path-selector.o dm-mpath.o
dm-snapshot-y += dm-snap.o dm-exception-store.o dm-snap-transient.o
dm-snap-persistent.o
diff --git a/drivers/md/dm-bio-prison.c b/drivers/md/dm-bio-prison.c
new file mode 100644
index 0000000..ddc4afc
--- /dev/null
+++ b/drivers/md/dm-bio-prison.c
@@ -0,0 +1,336 @@
+/*
+ * Copyright (C) 2012 Red Hat.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-bio-prison.h"
+
+#include <linux/module.h>
+
+/*----------------------------------------------------------------*/
+
+static uint32_t calc_nr_buckets(unsigned nr_cells)
+{
+ uint32_t n = 128;
+
+ nr_cells /= 4;
+ nr_cells = min(nr_cells, 8192u);
+
+ while (n < nr_cells)
+ n <<= 1;
+
+ return n;
+}
+
+/*
+ * @nr_cells should be the number of cells you want in use _concurrently_.
+ * Don't confuse it with the number of distinct keys.
+ */
+struct bio_prison *prison_create(unsigned nr_cells)
+{
+ unsigned i;
+ uint32_t nr_buckets = calc_nr_buckets(nr_cells);
+ size_t len = sizeof(struct bio_prison) +
+ (sizeof(struct hlist_head) * nr_buckets);
+ struct bio_prison *prison = kmalloc(len, GFP_KERNEL);
+
+ if (!prison)
+ return NULL;
+
+ spin_lock_init(&prison->lock);
+ prison->cell_pool = mempool_create_kmalloc_pool(nr_cells,
+ sizeof(struct cell));
+ if (!prison->cell_pool) {
+ kfree(prison);
+ return NULL;
+ }
+
+ prison->nr_buckets = nr_buckets;
+ prison->hash_mask = nr_buckets - 1;
+ prison->cells = (struct hlist_head *) (prison + 1);
+ for (i = 0; i < nr_buckets; i++)
+ INIT_HLIST_HEAD(prison->cells + i);
+
+ return prison;
+}
+EXPORT_SYMBOL(prison_create);
+
+void prison_destroy(struct bio_prison *prison)
+{
+ mempool_destroy(prison->cell_pool);
+ kfree(prison);
+}
+EXPORT_SYMBOL(prison_destroy);
+
+static uint32_t hash_key(struct bio_prison *prison, struct cell_key *key)
+{
+ const unsigned long BIG_PRIME = 4294967291UL;
+ uint64_t hash = key->block * BIG_PRIME;
+
+ return (uint32_t) (hash & prison->hash_mask);
+}
+
+static int keys_equal(struct cell_key *lhs, struct cell_key *rhs)
+{
+ return (lhs->virtual == rhs->virtual) &&
+ (lhs->dev == rhs->dev) &&
+ (lhs->block == rhs->block);
+}
+
+static struct cell *__search_bucket(struct hlist_head *bucket,
+ struct cell_key *key)
+{
+ struct cell *cell;
+ struct hlist_node *tmp;
+
+ hlist_for_each_entry(cell, tmp, bucket, list)
+ if (keys_equal(&cell->key, key))
+ return cell;
+
+ return NULL;
+}
+
+/*
+ * This may block if a new cell needs allocating. You must ensure that
+ * cells will be unlocked even if the calling thread is blocked.
+ *
+ * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
+ */
+int bio_detain(struct bio_prison *prison, struct cell_key *key,
+ struct bio *inmate, struct cell **ref)
+{
+ int r;
+ unsigned long flags;
+ uint32_t hash = hash_key(prison, key);
+ struct cell *uninitialized_var(cell), *cell2 = NULL;
+
+ BUG_ON(hash > prison->nr_buckets);
+
+ spin_lock_irqsave(&prison->lock, flags);
+ cell = __search_bucket(prison->cells + hash, key);
+
+ if (!cell) {
+ /*
+ * Allocate a new cell
+ */
+ spin_unlock_irqrestore(&prison->lock, flags);
+ cell2 = mempool_alloc(prison->cell_pool, GFP_NOIO);
+ spin_lock_irqsave(&prison->lock, flags);
+
+ /*
+ * We've been unlocked, so we have to double check that
+ * nobody else has inserted this cell in the meantime.
+ */
+ cell = __search_bucket(prison->cells + hash, key);
+
+ if (!cell) {
+ cell = cell2;
+ cell2 = NULL;
+
+ cell->prison = prison;
+ memcpy(&cell->key, key, sizeof(cell->key));
+ cell->holder = inmate;
+ bio_list_init(&cell->bios);
+ hlist_add_head(&cell->list, prison->cells + hash);
+ r = 0;
+
+ } else {
+ mempool_free(cell2, prison->cell_pool);
+ cell2 = NULL;
+ r = 1;
+ bio_list_add(&cell->bios, inmate);
+ }
+
+ } else {
+ r = 1;
+ bio_list_add(&cell->bios, inmate);
+ }
+ spin_unlock_irqrestore(&prison->lock, flags);
+
+ *ref = cell;
+ return r;
+}
+EXPORT_SYMBOL(bio_detain);
+
+/*
+ * @inmates must have been initialised prior to this call
+ */
+static void __cell_release(struct cell *cell, struct bio_list *inmates)
+{
+ struct bio_prison *prison = cell->prison;
+
+ hlist_del(&cell->list);
+
+ if (inmates) {
+ bio_list_add(inmates, cell->holder);
+ bio_list_merge(inmates, &cell->bios);
+ }
+
+ mempool_free(cell, prison->cell_pool);
+}
+
+void cell_release(struct cell *cell, struct bio_list *bios)
+{
+ unsigned long flags;
+ struct bio_prison *prison = cell->prison;
+
+ spin_lock_irqsave(&prison->lock, flags);
+ __cell_release(cell, bios);
+ spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL(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 cell *cell, struct bio *bio)
+{
+ hlist_del(&cell->list);
+ BUG_ON(cell->holder != bio);
+ BUG_ON(!bio_list_empty(&cell->bios));
+}
+
+void cell_release_singleton(struct cell *cell, struct bio *bio)
+{
+ unsigned long flags;
+ struct bio_prison *prison = cell->prison;
+
+ spin_lock_irqsave(&prison->lock, flags);
+ __cell_release_singleton(cell, bio);
+ spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL(cell_release_singleton);
+
+/*
+ * Sometimes we don't want the holder, just the additional bios.
+ */
+static void __cell_release_no_holder(struct cell *cell, struct bio_list *inmates)
+{
+ struct bio_prison *prison = cell->prison;
+
+ hlist_del(&cell->list);
+ if (inmates)
+ bio_list_merge(inmates, &cell->bios);
+
+ mempool_free(cell, prison->cell_pool);
+}
+
+void cell_release_no_holder(struct cell *cell, struct bio_list *inmates)
+{
+ unsigned long flags;
+ struct bio_prison *prison = cell->prison;
+
+ spin_lock_irqsave(&prison->lock, flags);
+ __cell_release_no_holder(cell, inmates);
+ spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL(cell_release_no_holder);
+
+void cell_error(struct cell *cell)
+{
+ struct bio_prison *prison = cell->prison;
+ struct bio_list bios;
+ struct bio *bio;
+ unsigned long flags;
+
+ bio_list_init(&bios);
+
+ spin_lock_irqsave(&prison->lock, flags);
+ __cell_release(cell, &bios);
+ spin_unlock_irqrestore(&prison->lock, flags);
+
+ while ((bio = bio_list_pop(&bios)))
+ bio_io_error(bio);
+}
+EXPORT_SYMBOL(cell_error);
+
+/*----------------------------------------------------------------*/
+
+void ds_init(struct deferred_set *ds)
+{
+ int i;
+
+ spin_lock_init(&ds->lock);
+ ds->current_entry = 0;
+ ds->sweeper = 0;
+ for (i = 0; i < DEFERRED_SET_SIZE; i++) {
+ ds->entries[i].ds = ds;
+ ds->entries[i].count = 0;
+ INIT_LIST_HEAD(&ds->entries[i].work_items);
+ }
+}
+EXPORT_SYMBOL(ds_init);
+
+struct deferred_entry *ds_inc(struct deferred_set *ds)
+{
+ unsigned long flags;
+ struct deferred_entry *entry;
+
+ spin_lock_irqsave(&ds->lock, flags);
+ entry = ds->entries + ds->current_entry;
+ entry->count++;
+ spin_unlock_irqrestore(&ds->lock, flags);
+
+ return entry;
+}
+EXPORT_SYMBOL(ds_inc);
+
+unsigned ds_next(unsigned index)
+{
+ return (index + 1) % DEFERRED_SET_SIZE;
+}
+
+static void __sweep(struct deferred_set *ds, struct list_head *head)
+{
+ while ((ds->sweeper != ds->current_entry) &&
+ !ds->entries[ds->sweeper].count) {
+ list_splice_init(&ds->entries[ds->sweeper].work_items, head);
+ ds->sweeper = ds_next(ds->sweeper);
+ }
+
+ if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
+ list_splice_init(&ds->entries[ds->sweeper].work_items, head);
+}
+
+void ds_dec(struct deferred_entry *entry, struct list_head *head)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&entry->ds->lock, flags);
+ BUG_ON(!entry->count);
+ --entry->count;
+ __sweep(entry->ds, head);
+ spin_unlock_irqrestore(&entry->ds->lock, flags);
+}
+EXPORT_SYMBOL(ds_dec);
+
+/*
+ * Returns 1 if deferred or 0 if no pending items to delay job.
+ */
+int ds_add_work(struct deferred_set *ds, struct list_head *work)
+{
+ int r = 1;
+ unsigned long flags;
+ unsigned next_entry;
+
+ spin_lock_irqsave(&ds->lock, flags);
+ if ((ds->sweeper == ds->current_entry) &&
+ !ds->entries[ds->current_entry].count)
+ r = 0;
+ else {
+ list_add(work, &ds->entries[ds->current_entry].work_items);
+ next_entry = ds_next(ds->current_entry);
+ if (!ds->entries[next_entry].count)
+ ds->current_entry = next_entry;
+ }
+ spin_unlock_irqrestore(&ds->lock, flags);
+
+ return r;
+}
+EXPORT_SYMBOL(ds_add_work);
+
+/*----------------------------------------------------------------*/
diff --git a/drivers/md/dm-bio-prison.h b/drivers/md/dm-bio-prison.h
new file mode 100644
index 0000000..ba428d0
--- /dev/null
+++ b/drivers/md/dm-bio-prison.h
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2012 Red Hat.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BIO_PRISON_H
+#define DM_BIO_PRISON_H
+
+#include "persistent-data/dm-block-manager.h"
+
+#include <linux/list.h>
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Device identifier
+ */
+typedef uint64_t dm_dev_id;
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Sometimes we can't deal with a bio straight away. We put them in prison
+ * where they can't cause any mischief. Bios are put in a cell identified
+ * by a key, multiple bios can be in the same cell. When the cell is
+ * subsequently unlocked the bios become available.
+ */
+struct bio_prison;
+
+struct cell_key {
+ int virtual;
+ dm_dev_id dev;
+ dm_block_t block;
+};
+
+struct cell {
+ struct hlist_node list;
+ struct bio_prison *prison;
+ struct cell_key key;
+ struct bio *holder;
+ struct bio_list bios;
+};
+
+struct bio_prison {
+ spinlock_t lock;
+ mempool_t *cell_pool;
+
+ unsigned nr_buckets;
+ unsigned hash_mask;
+ struct hlist_head *cells;
+};
+
+/*
+ * @nr_cells should be the number of cells you want in use _concurrently_.
+ * Don't confuse it with the number of distinct keys.
+ */
+struct bio_prison *prison_create(unsigned nr_cells);
+void prison_destroy(struct bio_prison *prison);
+
+/*
+ * This may block if a new cell needs allocating. You must ensure that
+ * cells will be unlocked even if the calling thread is blocked.
+ *
+ * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
+ */
+int bio_detain(struct bio_prison *prison, struct cell_key *key,
+ struct bio *inmate, struct cell **ref);
+void cell_release(struct cell *cell, struct bio_list *bios);
+void cell_release_singleton(struct cell *cell, struct bio *bio);
+void cell_release_no_holder(struct cell *cell, struct bio_list *inmates);
+void cell_error(struct cell *cell);
+
+/*----------------------------------------------------------------*/
+
+/*
+ * We use the deferred set to keep track of pending reads to shared blocks.
+ * We do this to ensure the new mapping caused by a write isn't performed
+ * until these prior reads have completed. Otherwise the insertion of the
+ * new mapping could free the old block that the read bios are mapped to.
+ */
+#define DEFERRED_SET_SIZE 64
+
+struct deferred_set;
+struct deferred_entry {
+ struct deferred_set *ds;
+ unsigned count;
+ struct list_head work_items;
+};
+
+struct deferred_set {
+ spinlock_t lock;
+ unsigned current_entry;
+ unsigned sweeper;
+ struct deferred_entry entries[DEFERRED_SET_SIZE];
+};
+
+void ds_init(struct deferred_set *ds);
+struct deferred_entry *ds_inc(struct deferred_set *ds);
+unsigned ds_next(unsigned index);
+void ds_dec(struct deferred_entry *entry, struct list_head *head);
+
+/*
+ * Returns 1 if deferred or 0 if no pending items to delay job.
+ */
+int ds_add_work(struct deferred_set *ds, struct list_head *work);
+
+/*----------------------------------------------------------------*/
+
+#endif
diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
index 511a223..d718189 100644
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -7,6 +7,7 @@
#ifndef DM_THIN_METADATA_H
#define DM_THIN_METADATA_H

+#include "dm-bio-prison.h"
#include "persistent-data/dm-block-manager.h"

#define THIN_METADATA_BLOCK_SIZE 4096
@@ -32,11 +33,6 @@ struct dm_pool_metadata;
struct dm_thin_device;

/*
- * Device identifier
- */
-typedef uint64_t dm_dev_id;
-
-/*
* Reopens or creates a new, empty metadata volume.
*/
struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 536835f..d0be4b0 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -4,6 +4,7 @@
* This file is released under the GPL.
*/

+#include "dm-bio-prison.h"
#include "dm-thin-metadata.h"

#include <linux/device-mapper.h>
@@ -20,7 +21,6 @@
* Tunable constants
*/
#define ENDIO_HOOK_POOL_SIZE 10240
-#define DEFERRED_SET_SIZE 64
#define MAPPING_POOL_SIZE 1024
#define PRISON_CELLS 1024
#define COMMIT_PERIOD HZ
@@ -98,372 +98,6 @@
/*----------------------------------------------------------------*/

/*
- * Sometimes we can't deal with a bio straight away. We put them in prison
- * where they can't cause any mischief. Bios are put in a cell identified
- * by a key, multiple bios can be in the same cell. When the cell is
- * subsequently unlocked the bios become available.
- */
-struct bio_prison;
-
-struct cell_key {
- int virtual;
- dm_dev_id dev;
- dm_block_t block;
-};
-
-struct cell {
- struct hlist_node list;
- struct bio_prison *prison;
- struct cell_key key;
- struct bio *holder;
- struct bio_list bios;
-};
-
-struct bio_prison {
- spinlock_t lock;
- mempool_t *cell_pool;
-
- unsigned nr_buckets;
- unsigned hash_mask;
- struct hlist_head *cells;
-};
-
-static uint32_t calc_nr_buckets(unsigned nr_cells)
-{
- uint32_t n = 128;
-
- nr_cells /= 4;
- nr_cells = min(nr_cells, 8192u);
-
- while (n < nr_cells)
- n <<= 1;
-
- return n;
-}
-
-/*
- * @nr_cells should be the number of cells you want in use _concurrently_.
- * Don't confuse it with the number of distinct keys.
- */
-static struct bio_prison *prison_create(unsigned nr_cells)
-{
- unsigned i;
- uint32_t nr_buckets = calc_nr_buckets(nr_cells);
- size_t len = sizeof(struct bio_prison) +
- (sizeof(struct hlist_head) * nr_buckets);
- struct bio_prison *prison = kmalloc(len, GFP_KERNEL);
-
- if (!prison)
- return NULL;
-
- spin_lock_init(&prison->lock);
- prison->cell_pool = mempool_create_kmalloc_pool(nr_cells,
- sizeof(struct cell));
- if (!prison->cell_pool) {
- kfree(prison);
- return NULL;
- }
-
- prison->nr_buckets = nr_buckets;
- prison->hash_mask = nr_buckets - 1;
- prison->cells = (struct hlist_head *) (prison + 1);
- for (i = 0; i < nr_buckets; i++)
- INIT_HLIST_HEAD(prison->cells + i);
-
- return prison;
-}
-
-static void prison_destroy(struct bio_prison *prison)
-{
- mempool_destroy(prison->cell_pool);
- kfree(prison);
-}
-
-static uint32_t hash_key(struct bio_prison *prison, struct cell_key *key)
-{
- const unsigned long BIG_PRIME = 4294967291UL;
- uint64_t hash = key->block * BIG_PRIME;
-
- return (uint32_t) (hash & prison->hash_mask);
-}
-
-static int keys_equal(struct cell_key *lhs, struct cell_key *rhs)
-{
- return (lhs->virtual == rhs->virtual) &&
- (lhs->dev == rhs->dev) &&
- (lhs->block == rhs->block);
-}
-
-static struct cell *__search_bucket(struct hlist_head *bucket,
- struct cell_key *key)
-{
- struct cell *cell;
- struct hlist_node *tmp;
-
- hlist_for_each_entry(cell, tmp, bucket, list)
- if (keys_equal(&cell->key, key))
- return cell;
-
- return NULL;
-}
-
-/*
- * This may block if a new cell needs allocating. You must ensure that
- * cells will be unlocked even if the calling thread is blocked.
- *
- * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
- */
-static int bio_detain(struct bio_prison *prison, struct cell_key *key,
- struct bio *inmate, struct cell **ref)
-{
- int r;
- unsigned long flags;
- uint32_t hash = hash_key(prison, key);
- struct cell *uninitialized_var(cell), *cell2 = NULL;
-
- BUG_ON(hash > prison->nr_buckets);
-
- spin_lock_irqsave(&prison->lock, flags);
- cell = __search_bucket(prison->cells + hash, key);
-
- if (!cell) {
- /*
- * Allocate a new cell
- */
- spin_unlock_irqrestore(&prison->lock, flags);
- cell2 = mempool_alloc(prison->cell_pool, GFP_NOIO);
- spin_lock_irqsave(&prison->lock, flags);
-
- /*
- * We've been unlocked, so we have to double check that
- * nobody else has inserted this cell in the meantime.
- */
- cell = __search_bucket(prison->cells + hash, key);
-
- if (!cell) {
- cell = cell2;
- cell2 = NULL;
-
- cell->prison = prison;
- memcpy(&cell->key, key, sizeof(cell->key));
- cell->holder = inmate;
- bio_list_init(&cell->bios);
- hlist_add_head(&cell->list, prison->cells + hash);
- r = 0;
-
- } else {
- mempool_free(cell2, prison->cell_pool);
- cell2 = NULL;
- r = 1;
- bio_list_add(&cell->bios, inmate);
- }
-
- } else {
- r = 1;
- bio_list_add(&cell->bios, inmate);
- }
- spin_unlock_irqrestore(&prison->lock, flags);
-
- *ref = cell;
- return r;
-}
-
-/*
- * @inmates must have been initialised prior to this call
- */
-static void __cell_release(struct cell *cell, struct bio_list *inmates)
-{
- struct bio_prison *prison = cell->prison;
-
- hlist_del(&cell->list);
-
- if (inmates) {
- bio_list_add(inmates, cell->holder);
- bio_list_merge(inmates, &cell->bios);
- }
-
- mempool_free(cell, prison->cell_pool);
-}
-
-static void cell_release(struct cell *cell, struct bio_list *bios)
-{
- unsigned long flags;
- struct bio_prison *prison = cell->prison;
-
- spin_lock_irqsave(&prison->lock, flags);
- __cell_release(cell, bios);
- spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-/*
- * 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 cell *cell, struct bio *bio)
-{
- hlist_del(&cell->list);
- BUG_ON(cell->holder != bio);
- BUG_ON(!bio_list_empty(&cell->bios));
-}
-
-static void cell_release_singleton(struct cell *cell, struct bio *bio)
-{
- unsigned long flags;
- struct bio_prison *prison = cell->prison;
-
- spin_lock_irqsave(&prison->lock, flags);
- __cell_release_singleton(cell, bio);
- spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-/*
- * Sometimes we don't want the holder, just the additional bios.
- */
-static void __cell_release_no_holder(struct cell *cell, struct bio_list *inmates)
-{
- struct bio_prison *prison = cell->prison;
-
- hlist_del(&cell->list);
- if (inmates)
- bio_list_merge(inmates, &cell->bios);
-
- mempool_free(cell, prison->cell_pool);
-}
-
-static void cell_release_no_holder(struct cell *cell, struct bio_list *inmates)
-{
- unsigned long flags;
- struct bio_prison *prison = cell->prison;
-
- spin_lock_irqsave(&prison->lock, flags);
- __cell_release_no_holder(cell, inmates);
- spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-static void cell_error(struct cell *cell)
-{
- struct bio_prison *prison = cell->prison;
- struct bio_list bios;
- struct bio *bio;
- unsigned long flags;
-
- bio_list_init(&bios);
-
- spin_lock_irqsave(&prison->lock, flags);
- __cell_release(cell, &bios);
- spin_unlock_irqrestore(&prison->lock, flags);
-
- while ((bio = bio_list_pop(&bios)))
- bio_io_error(bio);
-}
-
-/*----------------------------------------------------------------*/
-
-/*
- * We use the deferred set to keep track of pending reads to shared blocks.
- * We do this to ensure the new mapping caused by a write isn't performed
- * until these prior reads have completed. Otherwise the insertion of the
- * new mapping could free the old block that the read bios are mapped to.
- */
-
-struct deferred_set;
-struct deferred_entry {
- struct deferred_set *ds;
- unsigned count;
- struct list_head work_items;
-};
-
-struct deferred_set {
- spinlock_t lock;
- unsigned current_entry;
- unsigned sweeper;
- struct deferred_entry entries[DEFERRED_SET_SIZE];
-};
-
-static void ds_init(struct deferred_set *ds)
-{
- int i;
-
- spin_lock_init(&ds->lock);
- ds->current_entry = 0;
- ds->sweeper = 0;
- for (i = 0; i < DEFERRED_SET_SIZE; i++) {
- ds->entries[i].ds = ds;
- ds->entries[i].count = 0;
- INIT_LIST_HEAD(&ds->entries[i].work_items);
- }
-}
-
-static struct deferred_entry *ds_inc(struct deferred_set *ds)
-{
- unsigned long flags;
- struct deferred_entry *entry;
-
- spin_lock_irqsave(&ds->lock, flags);
- entry = ds->entries + ds->current_entry;
- entry->count++;
- spin_unlock_irqrestore(&ds->lock, flags);
-
- return entry;
-}
-
-static unsigned ds_next(unsigned index)
-{
- return (index + 1) % DEFERRED_SET_SIZE;
-}
-
-static void __sweep(struct deferred_set *ds, struct list_head *head)
-{
- while ((ds->sweeper != ds->current_entry) &&
- !ds->entries[ds->sweeper].count) {
- list_splice_init(&ds->entries[ds->sweeper].work_items, head);
- ds->sweeper = ds_next(ds->sweeper);
- }
-
- if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
- list_splice_init(&ds->entries[ds->sweeper].work_items, head);
-}
-
-static void ds_dec(struct deferred_entry *entry, struct list_head *head)
-{
- unsigned long flags;
-
- spin_lock_irqsave(&entry->ds->lock, flags);
- BUG_ON(!entry->count);
- --entry->count;
- __sweep(entry->ds, head);
- spin_unlock_irqrestore(&entry->ds->lock, flags);
-}
-
-/*
- * Returns 1 if deferred or 0 if no pending items to delay job.
- */
-static int ds_add_work(struct deferred_set *ds, struct list_head *work)
-{
- int r = 1;
- unsigned long flags;
- unsigned next_entry;
-
- spin_lock_irqsave(&ds->lock, flags);
- if ((ds->sweeper == ds->current_entry) &&
- !ds->entries[ds->current_entry].count)
- r = 0;
- else {
- list_add(work, &ds->entries[ds->current_entry].work_items);
- next_entry = ds_next(ds->current_entry);
- if (!ds->entries[next_entry].count)
- ds->current_entry = next_entry;
- }
- spin_unlock_irqrestore(&ds->lock, flags);
-
- return r;
-}
-
-/*----------------------------------------------------------------*/
-
-/*
* Key building.
*/
static void build_data_key(struct dm_thin_device *td,
--
1.7.1

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