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Old 03-19-2009, 08:37 PM
Jonathan Brassow
 
Default DM Snapshot: split ctr and dtr

Patch name: dm-snap-split-ctr-and-dtr.patch

Break up the snapshot constructor and destructor functions to
isolate the portions that allocate and initialize the dm_snapshot
structure. This structure will become the bulk of what is shared
as we move to a snapshot model that is tolerant of shared exception
stores. This will help us minimize code change as we add the new
sharing structures to the constructor/destructor procedure.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>

Index: linux-2.6/drivers/md/dm-snap.c
================================================== =================
--- linux-2.6.orig/drivers/md/dm-snap.c
+++ linux-2.6/drivers/md/dm-snap.c
@@ -431,6 +431,89 @@ static int create_exception_store(struct
argv + 2, store);
}

+static struct dm_snapshot *alloc_snapshot(sector_t hash_size)
+{
+ int r, i;
+ struct dm_snapshot *s;
+
+ s = kzalloc(sizeof(*s), GFP_KERNEL);
+ if (!s) {
+ DMERR("Cannot allocate snapshot structure");
+ return NULL;
+ }
+
+ s->valid = 1;
+ s->active = 0;
+ atomic_set(&s->pending_exceptions_count, 0);
+ init_rwsem(&s->lock);
+ spin_lock_init(&s->pe_lock);
+
+ /* Allocate hash table for pending COW data */
+ s->pending = dm_exception_table_create(hash_size, 0,
+ alloc_pending_exception, s,
+ free_pending_exception, NULL);
+ if (!s->pending) {
+ DMERR("Unable to allocate hash table space");
+ goto bad_hash_table;
+ }
+
+ r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
+ if (r) {
+ DMERR("Could not create kcopyd client");
+ goto bad_kcopyd;
+ }
+
+ s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
+ if (!s->pending_pool) {
+ DMERR("Could not allocate mempool for pending exceptions");
+ goto bad_pending_pool;
+ }
+
+ s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
+ tracked_chunk_cache);
+ if (!s->tracked_chunk_pool) {
+ DMERR("Could not allocate tracked_chunk mempool "
+ "for tracking reads");
+ goto bad_tracked_chunk_pool;
+ }
+
+ for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
+ INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
+
+ spin_lock_init(&s->tracked_chunk_lock);
+ bio_list_init(&s->queued_bios);
+ INIT_WORK(&s->queued_bios_work, flush_queued_bios);
+
+ return s;
+
+bad_tracked_chunk_pool:
+ mempool_destroy(s->pending_pool);
+
+bad_pending_pool:
+ dm_kcopyd_client_destroy(s->kcopyd_client);
+
+bad_kcopyd:
+ dm_exception_table_destroy(s->pending);
+
+bad_hash_table:
+ kfree(s);
+
+ return NULL;
+}
+
+static void dealloc_snapshot(struct dm_snapshot *s)
+{
+ mempool_destroy(s->tracked_chunk_pool);
+
+ mempool_destroy(s->pending_pool);
+
+ dm_kcopyd_client_destroy(s->kcopyd_client);
+
+ dm_exception_table_destroy(s->pending);
+
+ kfree(s);
+}
+
/*
* snapshot_ctr
* @ti
@@ -446,6 +529,7 @@ static int create_exception_store(struct
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
+ struct dm_dev *origin;
struct dm_snapshot *s;
int i;
int r = -EINVAL;
@@ -463,38 +547,26 @@ static int snapshot_ctr(struct dm_target
argc--;

r = create_exception_store(ti, argc, argv, &args_used, &store);
- if (r)
+ if (r) {
+ ti->error = "Failed to create snapshot exception store";
return r;
+ }

argv += args_used;
argc -= args_used;

- s = kmalloc(sizeof(*s), GFP_KERNEL);
- if (!s) {
- ti->error = "Cannot allocate snapshot private structure";
- r = -ENOMEM;
- goto bad_snap;
- }
-
- r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
+ r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &origin);
if (r) {
ti->error = "Cannot get origin device";
goto bad_origin;
}

- s->store = store;
- s->valid = 1;
- s->active = 0;
- atomic_set(&s->pending_exceptions_count, 0);
- init_rwsem(&s->lock);
- spin_lock_init(&s->pe_lock);
-
/*
* Calculate based on the size of the original volume or
* the COW volume...
*/
cow_dev_size = get_dev_size(store->cow->bdev);
- origin_dev_size = get_dev_size(s->origin->bdev);
+ origin_dev_size = get_dev_size(origin->bdev);
max_buckets = calc_max_buckets();

hash_size = min(origin_dev_size, cow_dev_size) >> store->chunk_shift;
@@ -505,47 +577,24 @@ static int snapshot_ctr(struct dm_target
if (hash_size < 64)
hash_size = 64;

- s->pending = dm_exception_table_create(hash_size, 0,
- alloc_pending_exception, s,
- free_pending_exception, NULL);
- if (!s->pending) {
- ti->error = "Unable to allocate hash table space";
+ /*
+ * Allocate the snapshot
+ */
+ s = alloc_snapshot(hash_size);
+ if (!s) {
r = -ENOMEM;
- goto bad_hash_table;
- }
-
- r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
- if (r) {
- ti->error = "Could not create kcopyd client";
- goto bad_kcopyd;
- }
-
- s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
- if (!s->pending_pool) {
- ti->error = "Could not allocate mempool for pending exceptions";
- goto bad_pending_pool;
- }
-
- s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
- tracked_chunk_cache);
- if (!s->tracked_chunk_pool) {
- ti->error = "Could not allocate tracked_chunk mempool for "
- "tracking reads";
- goto bad_tracked_chunk_pool;
+ ti->error = "Failed to create snapshot structure";
+ goto bad_alloc_snapshot;
}

- for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
- INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
-
- spin_lock_init(&s->tracked_chunk_lock);
- bio_list_init(&s->queued_bios);
- INIT_WORK(&s->queued_bios_work, flush_queued_bios);
+ s->origin = origin;
+ s->store = store;

/* Add snapshot to the list of snapshots for this origin */
/* Exceptions aren't triggered till snapshot_resume() is called */
if (register_snapshot(s)) {
r = -EINVAL;
- ti->error = "Cannot register snapshot origin";
+ ti->error = "Cannot register snapshot with origin";
goto bad_load_and_register;
}

@@ -555,24 +604,12 @@ static int snapshot_ctr(struct dm_target
return 0;

bad_load_and_register:
- mempool_destroy(s->tracked_chunk_pool);
-
-bad_tracked_chunk_pool:
- mempool_destroy(s->pending_pool);
-
-bad_pending_pool:
- dm_kcopyd_client_destroy(s->kcopyd_client);
+ dealloc_snapshot(s);

-bad_kcopyd:
- dm_exception_table_destroy(s->pending);
-
-bad_hash_table:
- dm_put_device(ti, s->origin);
+bad_alloc_snapshot:
+ dm_put_device(ti, origin);

bad_origin:
- kfree(s);
-
-bad_snap:
dm_exception_store_destroy(store);

return r;
@@ -604,20 +641,11 @@ static void snapshot_dtr(struct dm_targe
BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
#endif

- mempool_destroy(s->tracked_chunk_pool);
-
- dm_kcopyd_client_destroy(s->kcopyd_client);
- s->kcopyd_client = NULL;
-
- dm_exception_table_destroy(s->pending);
-
- mempool_destroy(s->pending_pool);
-
dm_put_device(ti, s->origin);

dm_exception_store_destroy(s->store);

- kfree(s);
+ dealloc_snapshot(s);
}

/*

--
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dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel
 
Old 03-25-2009, 08:38 PM
Jonathan Brassow
 
Default DM Snapshot: split ctr and dtr

Patch name: dm-snap-split-ctr-and-dtr.patch

Break up the snapshot constructor and destructor functions to
isolate the portions that allocate and initialize the dm_snapshot
structure. This structure will become the bulk of what is shared
as we move to a snapshot model that is tolerant of shared exception
stores. This will help us minimize code change as we add the new
sharing structures to the constructor/destructor procedure.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>

Index: linux-2.6/drivers/md/dm-snap.c
================================================== =================
--- linux-2.6.orig/drivers/md/dm-snap.c
+++ linux-2.6/drivers/md/dm-snap.c
@@ -431,6 +431,89 @@ static int create_exception_store(struct
argv + 2, store);
}

+static struct dm_snapshot *alloc_snapshot(sector_t hash_size)
+{
+ int r, i;
+ struct dm_snapshot *s;
+
+ s = kzalloc(sizeof(*s), GFP_KERNEL);
+ if (!s) {
+ DMERR("Cannot allocate snapshot structure");
+ return NULL;
+ }
+
+ s->valid = 1;
+ s->active = 0;
+ atomic_set(&s->pending_exceptions_count, 0);
+ init_rwsem(&s->lock);
+ spin_lock_init(&s->pe_lock);
+
+ /* Allocate hash table for pending COW data */
+ s->pending = dm_exception_table_create(hash_size, 0,
+ alloc_pending_exception, s,
+ free_pending_exception, NULL);
+ if (!s->pending) {
+ DMERR("Unable to allocate hash table space");
+ goto bad_hash_table;
+ }
+
+ r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
+ if (r) {
+ DMERR("Could not create kcopyd client");
+ goto bad_kcopyd;
+ }
+
+ s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
+ if (!s->pending_pool) {
+ DMERR("Could not allocate mempool for pending exceptions");
+ goto bad_pending_pool;
+ }
+
+ s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
+ tracked_chunk_cache);
+ if (!s->tracked_chunk_pool) {
+ DMERR("Could not allocate tracked_chunk mempool "
+ "for tracking reads");
+ goto bad_tracked_chunk_pool;
+ }
+
+ for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
+ INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
+
+ spin_lock_init(&s->tracked_chunk_lock);
+ bio_list_init(&s->queued_bios);
+ INIT_WORK(&s->queued_bios_work, flush_queued_bios);
+
+ return s;
+
+bad_tracked_chunk_pool:
+ mempool_destroy(s->pending_pool);
+
+bad_pending_pool:
+ dm_kcopyd_client_destroy(s->kcopyd_client);
+
+bad_kcopyd:
+ dm_exception_table_destroy(s->pending);
+
+bad_hash_table:
+ kfree(s);
+
+ return NULL;
+}
+
+static void dealloc_snapshot(struct dm_snapshot *s)
+{
+ mempool_destroy(s->tracked_chunk_pool);
+
+ mempool_destroy(s->pending_pool);
+
+ dm_kcopyd_client_destroy(s->kcopyd_client);
+
+ dm_exception_table_destroy(s->pending);
+
+ kfree(s);
+}
+
/*
* snapshot_ctr
* @ti
@@ -446,6 +529,7 @@ static int create_exception_store(struct
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
+ struct dm_dev *origin;
struct dm_snapshot *s;
int i;
int r = -EINVAL;
@@ -463,38 +547,26 @@ static int snapshot_ctr(struct dm_target
argc--;

r = create_exception_store(ti, argc, argv, &args_used, &store);
- if (r)
+ if (r) {
+ ti->error = "Failed to create snapshot exception store";
return r;
+ }

argv += args_used;
argc -= args_used;

- s = kmalloc(sizeof(*s), GFP_KERNEL);
- if (!s) {
- ti->error = "Cannot allocate snapshot private structure";
- r = -ENOMEM;
- goto bad_snap;
- }
-
- r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
+ r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &origin);
if (r) {
ti->error = "Cannot get origin device";
goto bad_origin;
}

- s->store = store;
- s->valid = 1;
- s->active = 0;
- atomic_set(&s->pending_exceptions_count, 0);
- init_rwsem(&s->lock);
- spin_lock_init(&s->pe_lock);
-
/*
* Calculate based on the size of the original volume or
* the COW volume...
*/
cow_dev_size = get_dev_size(store->cow->bdev);
- origin_dev_size = get_dev_size(s->origin->bdev);
+ origin_dev_size = get_dev_size(origin->bdev);
max_buckets = calc_max_buckets();

hash_size = min(origin_dev_size, cow_dev_size) >> store->chunk_shift;
@@ -505,47 +577,24 @@ static int snapshot_ctr(struct dm_target
if (hash_size < 64)
hash_size = 64;

- s->pending = dm_exception_table_create(hash_size, 0,
- alloc_pending_exception, s,
- free_pending_exception, NULL);
- if (!s->pending) {
- ti->error = "Unable to allocate hash table space";
+ /*
+ * Allocate the snapshot
+ */
+ s = alloc_snapshot(hash_size);
+ if (!s) {
r = -ENOMEM;
- goto bad_hash_table;
- }
-
- r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
- if (r) {
- ti->error = "Could not create kcopyd client";
- goto bad_kcopyd;
- }
-
- s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
- if (!s->pending_pool) {
- ti->error = "Could not allocate mempool for pending exceptions";
- goto bad_pending_pool;
- }
-
- s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
- tracked_chunk_cache);
- if (!s->tracked_chunk_pool) {
- ti->error = "Could not allocate tracked_chunk mempool for "
- "tracking reads";
- goto bad_tracked_chunk_pool;
+ ti->error = "Failed to create snapshot structure";
+ goto bad_alloc_snapshot;
}

- for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
- INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
-
- spin_lock_init(&s->tracked_chunk_lock);
- bio_list_init(&s->queued_bios);
- INIT_WORK(&s->queued_bios_work, flush_queued_bios);
+ s->origin = origin;
+ s->store = store;

/* Add snapshot to the list of snapshots for this origin */
/* Exceptions aren't triggered till snapshot_resume() is called */
if (register_snapshot(s)) {
r = -EINVAL;
- ti->error = "Cannot register snapshot origin";
+ ti->error = "Cannot register snapshot with origin";
goto bad_load_and_register;
}

@@ -555,24 +604,12 @@ static int snapshot_ctr(struct dm_target
return 0;

bad_load_and_register:
- mempool_destroy(s->tracked_chunk_pool);
-
-bad_tracked_chunk_pool:
- mempool_destroy(s->pending_pool);
-
-bad_pending_pool:
- dm_kcopyd_client_destroy(s->kcopyd_client);
+ dealloc_snapshot(s);

-bad_kcopyd:
- dm_exception_table_destroy(s->pending);
-
-bad_hash_table:
- dm_put_device(ti, s->origin);
+bad_alloc_snapshot:
+ dm_put_device(ti, origin);

bad_origin:
- kfree(s);
-
-bad_snap:
dm_exception_store_destroy(store);

return r;
@@ -604,20 +641,11 @@ static void snapshot_dtr(struct dm_targe
BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
#endif

- mempool_destroy(s->tracked_chunk_pool);
-
- dm_kcopyd_client_destroy(s->kcopyd_client);
- s->kcopyd_client = NULL;
-
- dm_exception_table_destroy(s->pending);
-
- mempool_destroy(s->pending_pool);
-
dm_put_device(ti, s->origin);

dm_exception_store_destroy(s->store);

- kfree(s);
+ dealloc_snapshot(s);
}

/*

--
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https://www.redhat.com/mailman/listinfo/dm-devel
 

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