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dm bio prison: pass cell memory in

Browse source 
Change the dm_bio_prison interface so that instead of allocating memory
internally, dm_bio_detain is supplied with a pre-allocated cell each
time it is called.

This enables a subsequent patch to move the allocation of the struct
dm_bio_prison_cell outside the thin target's mapping function so it can
no longer block there.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Joe Thornber 2013-03-01 22:45:50 +00:00 committed by Alasdair G Kergon
parent 4e7f1f9089
commit 6beca5eb6e
3 changed files with 178 additions and 103 deletions
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145
drivers/md/dm-bio-prison.c
View file

@ -16,7 +16,6 @@
struct dm_bio_prison_cell {
struct hlist_node list;
struct dm_bio_prison *prison;
struct dm_cell_key key;
struct bio *holder;
struct bio_list bios;
@ -87,6 +86,19 @@ void dm_bio_prison_destroy(struct dm_bio_prison *prison)
}
EXPORT_SYMBOL_GPL(dm_bio_prison_destroy);
struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison, gfp_t gfp)
{
return mempool_alloc(prison->cell_pool, gfp);
}
EXPORT_SYMBOL_GPL(dm_bio_prison_alloc_cell);
void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell)
{
mempool_free(cell, prison->cell_pool);
}
EXPORT_SYMBOL_GPL(dm_bio_prison_free_cell);
static uint32_t hash_key(struct dm_bio_prison *prison, struct dm_cell_key *key)
{
const unsigned long BIG_PRIME = 4294967291UL;
@ -114,91 +126,86 @@ static struct dm_bio_prison_cell *__search_bucket(struct hlist_head *bucket,
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 dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
struct bio *inmate, struct dm_bio_prison_cell **ref)
static void __setup_new_cell(struct dm_bio_prison *prison,
struct dm_cell_key *key,
struct bio *holder,
uint32_t hash,
struct dm_bio_prison_cell *cell)
{
int r = 1;
unsigned long flags;
uint32_t hash = hash_key(prison, key);
struct dm_bio_prison_cell *cell, *cell2;
BUG_ON(hash > prison->nr_buckets);
spin_lock_irqsave(&prison->lock, flags);
cell = __search_bucket(prison->cells + hash, key);
if (cell) {
bio_list_add(&cell->bios, inmate);
goto out;
}
/*
* 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) {
mempool_free(cell2, prison->cell_pool);
bio_list_add(&cell->bios, inmate);
goto out;
}
/*
* Use new cell.
*/
cell = cell2;
cell->prison = prison;
memcpy(&cell->key, key, sizeof(cell->key));
cell->holder = inmate;
cell->holder = holder;
bio_list_init(&cell->bios);
hlist_add_head(&cell->list, prison->cells + hash);
}
r = 0;
static int __bio_detain(struct dm_bio_prison *prison,
struct dm_cell_key *key,
struct bio *inmate,
struct dm_bio_prison_cell *cell_prealloc,
struct dm_bio_prison_cell **cell_result)
{
uint32_t hash = hash_key(prison, key);
struct dm_bio_prison_cell *cell;
out:
cell = __search_bucket(prison->cells + hash, key);
if (cell) {
if (inmate)
bio_list_add(&cell->bios, inmate);
*cell_result = cell;
return 1;
}
__setup_new_cell(prison, key, inmate, hash, cell_prealloc);
*cell_result = cell_prealloc;
return 0;
}
static int bio_detain(struct dm_bio_prison *prison,
struct dm_cell_key *key,
struct bio *inmate,
struct dm_bio_prison_cell *cell_prealloc,
struct dm_bio_prison_cell **cell_result)
{
int r;
unsigned long flags;
spin_lock_irqsave(&prison->lock, flags);
r = __bio_detain(prison, key, inmate, cell_prealloc, cell_result);
spin_unlock_irqrestore(&prison->lock, flags);
*ref = cell;
return r;
}
int dm_bio_detain(struct dm_bio_prison *prison,
struct dm_cell_key *key,
struct bio *inmate,
struct dm_bio_prison_cell *cell_prealloc,
struct dm_bio_prison_cell **cell_result)
{
return bio_detain(prison, key, inmate, cell_prealloc, cell_result);
}
EXPORT_SYMBOL_GPL(dm_bio_detain);
/*
* @inmates must have been initialised prior to this call
*/
static void __cell_release(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
static void __cell_release(struct dm_bio_prison_cell *cell,
struct bio_list *inmates)
{
struct dm_bio_prison *prison = cell->prison;
hlist_del(&cell->list);
if (inmates) {
bio_list_add(inmates, cell->holder);
if (cell->holder)
bio_list_add(inmates, cell->holder);
bio_list_merge(inmates, &cell->bios);
}
mempool_free(cell, prison->cell_pool);
}
void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios)
void dm_cell_release(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell,
struct bio_list *bios)
{
unsigned long flags;
struct dm_bio_prison *prison = cell->prison;
spin_lock_irqsave(&prison->lock, flags);
__cell_release(cell, bios);
@ -209,20 +216,18 @@ EXPORT_SYMBOL_GPL(dm_cell_release);
/*
* Sometimes we don't want the holder, just the additional bios.
*/
static void __cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
static void __cell_release_no_holder(struct dm_bio_prison_cell *cell,
struct bio_list *inmates)
{
struct dm_bio_prison *prison = cell->prison;
hlist_del(&cell->list);
bio_list_merge(inmates, &cell->bios);
mempool_free(cell, prison->cell_pool);
}
void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
void dm_cell_release_no_holder(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell,
struct bio_list *inmates)
{
unsigned long flags;
struct dm_bio_prison *prison = cell->prison;
spin_lock_irqsave(&prison->lock, flags);
__cell_release_no_holder(cell, inmates);
@ -230,9 +235,9 @@ void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list
}
EXPORT_SYMBOL_GPL(dm_cell_release_no_holder);
void dm_cell_error(struct dm_bio_prison_cell *cell)
void dm_cell_error(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell)
{
struct dm_bio_prison *prison = cell->prison;
struct bio_list bios;
struct bio *bio;
unsigned long flags;

33
drivers/md/dm-bio-prison.h
View file

@ -35,17 +35,36 @@ struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
void dm_bio_prison_destroy(struct dm_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.
* These two functions just wrap a mempool. This is a transitory step:
* Eventually all bio prison clients should manage their own cell memory.
*
* Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
* in interrupt context or passed GFP_NOWAIT.
*/
struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
gfp_t gfp);
void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell);
/*
* An atomic op that combines retrieving a cell, and adding a bio to it.
*
* Returns 1 if the cell was already held, 0 if @inmate is the new holder.
*/
int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
struct bio *inmate, struct dm_bio_prison_cell **ref);
int dm_bio_detain(struct dm_bio_prison *prison,
struct dm_cell_key *key,
struct bio *inmate,
struct dm_bio_prison_cell *cell_prealloc,
struct dm_bio_prison_cell **cell_result);
void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios);
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);
void dm_cell_release(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell,
struct bio_list *bios);
void dm_cell_release_no_holder(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell,
struct bio_list *inmates);
void dm_cell_error(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell);
/*----------------------------------------------------------------*/

103
drivers/md/dm-thin.c
View file

@ -229,6 +229,54 @@ struct thin_c {
/*----------------------------------------------------------------*/
static int bio_detain(struct pool *pool, struct dm_cell_key *key, struct bio *bio,
struct dm_bio_prison_cell **cell_result)
{
int r;
struct dm_bio_prison_cell *cell_prealloc;
/*
* Allocate a cell from the prison's mempool.
* This might block but it can't fail.
*/
cell_prealloc = dm_bio_prison_alloc_cell(pool->prison, GFP_NOIO);
r = dm_bio_detain(pool->prison, key, bio, cell_prealloc, cell_result);
if (r)
/*
* We reused an old cell; we can get rid of
* the new one.
*/
dm_bio_prison_free_cell(pool->prison, cell_prealloc);
return r;
}
static void cell_release(struct pool *pool,
struct dm_bio_prison_cell *cell,
struct bio_list *bios)
{
dm_cell_release(pool->prison, cell, bios);
dm_bio_prison_free_cell(pool->prison, cell);
}
static void cell_release_no_holder(struct pool *pool,
struct dm_bio_prison_cell *cell,
struct bio_list *bios)
{
dm_cell_release_no_holder(pool->prison, cell, bios);
dm_bio_prison_free_cell(pool->prison, cell);
}
static void cell_error(struct pool *pool,
struct dm_bio_prison_cell *cell)
{
dm_cell_error(pool->prison, cell);
dm_bio_prison_free_cell(pool->prison, cell);
}
/*----------------------------------------------------------------*/
/*
* A global list of pools that uses a struct mapped_device as a key.
*/
@ -524,14 +572,14 @@ static void cell_defer(struct thin_c *tc, struct dm_bio_prison_cell *cell)
unsigned long flags;
spin_lock_irqsave(&pool->lock, flags);
dm_cell_release(cell, &pool->deferred_bios);
cell_release(pool, cell, &pool->deferred_bios);
spin_unlock_irqrestore(&tc->pool->lock, flags);
wake_worker(pool);
}
/*
* Same as cell_defer except it omits the original holder of the cell.
* Same as cell_defer above, except it omits the original holder of the cell.
*/
static void cell_defer_no_holder(struct thin_c *tc, struct dm_bio_prison_cell *cell)
{
@ -539,7 +587,7 @@ static void cell_defer_no_holder(struct thin_c *tc, struct dm_bio_prison_cell *c
unsigned long flags;
spin_lock_irqsave(&pool->lock, flags);
dm_cell_release_no_holder(cell, &pool->deferred_bios);
cell_release_no_holder(pool, cell, &pool->deferred_bios);
spin_unlock_irqrestore(&pool->lock, flags);
wake_worker(pool);
@ -549,13 +597,14 @@ static void process_prepared_mapping_fail(struct dm_thin_new_mapping *m)
{
if (m->bio)
m->bio->bi_end_io = m->saved_bi_end_io;
dm_cell_error(m->cell);
cell_error(m->tc->pool, m->cell);
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;
struct pool *pool = tc->pool;
struct bio *bio;
int r;
@ -564,7 +613,7 @@ static void process_prepared_mapping(struct dm_thin_new_mapping *m)
bio->bi_end_io = m->saved_bi_end_io;
if (m->err) {
dm_cell_error(m->cell);
cell_error(pool, m->cell);
goto out;
}
@ -576,7 +625,7 @@ static void process_prepared_mapping(struct dm_thin_new_mapping *m)
r = dm_thin_insert_block(tc->td, m->virt_block, m->data_block);
if (r) {
DMERR_LIMIT("dm_thin_insert_block() failed");
dm_cell_error(m->cell);
cell_error(pool, m->cell);
goto out;
}
@ -594,7 +643,7 @@ static void process_prepared_mapping(struct dm_thin_new_mapping *m)
out:
list_del(&m->list);
mempool_free(m, tc->pool->mapping_pool);
mempool_free(m, pool->mapping_pool);
}
static void process_prepared_discard_fail(struct dm_thin_new_mapping *m)
@ -745,7 +794,7 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
if (r < 0) {
mempool_free(m, pool->mapping_pool);
DMERR_LIMIT("dm_kcopyd_copy() failed");
dm_cell_error(cell);
cell_error(pool, cell);
}
}
}
@ -811,7 +860,7 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
if (r < 0) {
mempool_free(m, pool->mapping_pool);
DMERR_LIMIT("dm_kcopyd_zero() failed");
dm_cell_error(cell);
cell_error(pool, cell);
}
}
}
@ -917,13 +966,13 @@ static void retry_on_resume(struct bio *bio)
spin_unlock_irqrestore(&pool->lock, flags);
}
static void no_space(struct dm_bio_prison_cell *cell)
static void no_space(struct pool *pool, struct dm_bio_prison_cell *cell)
{
struct bio *bio;
struct bio_list bios;
bio_list_init(&bios);
dm_cell_release(cell, &bios);
cell_release(pool, cell, &bios);
while ((bio = bio_list_pop(&bios)))
retry_on_resume(bio);
@ -941,7 +990,7 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
struct dm_thin_new_mapping *m;
build_virtual_key(tc->td, block, &key);
if (dm_bio_detain(tc->pool->prison, &key, bio, &cell))
if (bio_detain(tc->pool, &key, bio, &cell))
return;
r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
@ -953,7 +1002,7 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
* on this block.
*/
build_data_key(tc->td, lookup_result.block, &key2);
if (dm_bio_detain(tc->pool->prison, &key2, bio, &cell2)) {
if (bio_detain(tc->pool, &key2, bio, &cell2)) {
cell_defer_no_holder(tc, cell);
break;
}
@ -1029,13 +1078,13 @@ static void break_sharing(struct thin_c *tc, struct bio *bio, dm_block_t block,
break;
case -ENOSPC:
no_space(cell);
no_space(tc->pool, cell);
break;
default:
DMERR_LIMIT("%s: alloc_data_block() failed: error = %d",
__func__, r);
dm_cell_error(cell);
cell_error(tc->pool, cell);
break;
}
}
@ -1053,7 +1102,7 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
* of being broken so we have nothing further to do here.
*/
build_data_key(tc->td, lookup_result->block, &key);
if (dm_bio_detain(pool->prison, &key, bio, &cell))
if (bio_detain(pool, &key, bio, &cell))
return;
if (bio_data_dir(bio) == WRITE && bio->bi_size)
@ -1074,12 +1123,13 @@ static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block
{
int r;
dm_block_t data_block;
struct pool *pool = tc->pool;
/*
* Remap empty bios (flushes) immediately, without provisioning.
*/
if (!bio->bi_size) {
inc_all_io_entry(tc->pool, bio);
inc_all_io_entry(pool, bio);
cell_defer_no_holder(tc, cell);
remap_and_issue(tc, bio, 0);
@ -1106,14 +1156,14 @@ static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block
break;
case -ENOSPC:
no_space(cell);
no_space(pool, cell);
break;
default:
DMERR_LIMIT("%s: alloc_data_block() failed: error = %d",
__func__, r);
set_pool_mode(tc->pool, PM_READ_ONLY);
dm_cell_error(cell);
set_pool_mode(pool, PM_READ_ONLY);
cell_error(pool, cell);
break;
}
}
@ -1121,6 +1171,7 @@ static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block
static void process_bio(struct thin_c *tc, struct bio *bio)
{
int r;
struct pool *pool = tc->pool;
dm_block_t block = get_bio_block(tc, bio);
struct dm_bio_prison_cell *cell;
struct dm_cell_key key;
@ -1131,7 +1182,7 @@ static void process_bio(struct thin_c *tc, struct bio *bio)
* being provisioned so we have nothing further to do here.
*/
build_virtual_key(tc->td, block, &key);
if (dm_bio_detain(tc->pool->prison, &key, bio, &cell))
if (bio_detain(pool, &key, bio, &cell))
return;
r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
@ -1139,9 +1190,9 @@ static void process_bio(struct thin_c *tc, struct bio *bio)
case 0:
if (lookup_result.shared) {
process_shared_bio(tc, bio, block, &lookup_result);
cell_defer_no_holder(tc, cell);
cell_defer_no_holder(tc, cell); /* FIXME: pass this cell into process_shared? */
} else {
inc_all_io_entry(tc->pool, bio);
inc_all_io_entry(pool, bio);
cell_defer_no_holder(tc, cell);
remap_and_issue(tc, bio, lookup_result.block);
@ -1150,7 +1201,7 @@ static void process_bio(struct thin_c *tc, struct bio *bio)
case -ENODATA:
if (bio_data_dir(bio) == READ && tc->origin_dev) {
inc_all_io_entry(tc->pool, bio);
inc_all_io_entry(pool, bio);
cell_defer_no_holder(tc, cell);
remap_to_origin_and_issue(tc, bio);
@ -1429,11 +1480,11 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
}
build_virtual_key(tc->td, block, &key);
if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1))
if (bio_detain(tc->pool, &key, bio, &cell1))
return DM_MAPIO_SUBMITTED;
build_data_key(tc->td, result.block, &key);
if (dm_bio_detain(tc->pool->prison, &key, bio, &cell2)) {
if (bio_detain(tc->pool, &key, bio, &cell2)) {
cell_defer_no_holder(tc, cell1);
return DM_MAPIO_SUBMITTED;
}