dm.c: protect md->map with a rw spin lock rather than the md->lock
semaphore. Also ensure that everyone accesses md->map through
dm_get_table(), rather than directly.
--- diff/drivers/md/dm-table.c 2004-03-09 11:51:50.000000000 +0000
+++ source/drivers/md/dm-table.c 2004-03-09 11:52:55.000000000 +0000
@@ -279,6 +279,9 @@ void dm_table_get(struct dm_table *t)
void dm_table_put(struct dm_table *t)
{
+ if (!t)
+ return;
+
if (atomic_dec_and_test(&t->holders))
table_destroy(t);
}
--- diff/drivers/md/dm.c 2004-03-09 11:51:50.000000000 +0000
+++ source/drivers/md/dm.c 2004-03-09 11:52:58.000000000 +0000
@@ -49,7 +49,7 @@ struct target_io {
struct mapped_device {
struct rw_semaphore lock;
- rwlock_t maplock;
+ rwlock_t map_lock;
atomic_t holders;
unsigned long flags;
@@ -238,6 +238,24 @@ static int queue_io(struct mapped_device
return 0; /* deferred successfully */
}
+/*
+ * Everyone (including functions in this file), should use this
+ * function to access the md->map field, and make sure they call
+ * dm_table_put() when finished.
+ */
+struct dm_table *dm_get_table(struct mapped_device *md)
+{
+ struct dm_table *t;
+
+ read_lock(&md->map_lock);
+ t = md->map;
+ if (t)
+ dm_table_get(t);
+ read_unlock(&md->map_lock);
+
+ return t;
+}
+
/*-----------------------------------------------------------------
* CRUD START:
* A more elegant soln is in the works that uses the queue
@@ -346,6 +364,7 @@ static void __map_bio(struct dm_target *
struct clone_info {
struct mapped_device *md;
+ struct dm_table *map;
struct bio *bio;
struct dm_io *io;
sector_t sector;
@@ -399,7 +418,7 @@ static struct bio *clone_bio(struct bio
static void __clone_and_map(struct clone_info *ci)
{
struct bio *clone, *bio = ci->bio;
- struct dm_target *ti = dm_table_find_target(ci->md->map, ci->sector);
+ struct dm_target *ti = dm_table_find_target(ci->map, ci->sector);
sector_t len = 0, max = max_io_len(ci->md, ci->sector, ti);
struct target_io *tio;
@@ -460,7 +479,7 @@ static void __clone_and_map(struct clone
ci->sector += max;
ci->sector_count -= max;
- ti = dm_table_find_target(ci->md->map, ci->sector);
+ ti = dm_table_find_target(ci->map, ci->sector);
len = to_sector(bv->bv_len) - max;
clone = split_bvec(bio, ci->sector, ci->idx,
@@ -484,6 +503,12 @@ static void __split_bio(struct mapped_de
{
struct clone_info ci;
+ ci.map = dm_get_table(md);
+ if (!ci.map) {
+ bio_io_error(bio, bio->bi_size);
+ return;
+ }
+
ci.md = md;
ci.bio = bio;
ci.io = alloc_io(md);
@@ -501,22 +526,12 @@ static void __split_bio(struct mapped_de
/* drop the extra reference count */
dec_pending(ci.io, 0);
+ dm_table_put(ci.map);
}
/*-----------------------------------------------------------------
* CRUD END
*---------------------------------------------------------------*/
-
-static inline void __dm_request(struct mapped_device *md, struct bio *bio)
-{
- if (!md->map) {
- bio_io_error(bio, bio->bi_size);
- return;
- }
-
- __split_bio(md, bio);
-}
-
/*
* The request function that just remaps the bio built up by
* dm_merge_bvec.
@@ -555,7 +570,7 @@ static int dm_request(request_queue_t *q
down_read(&md->lock);
}
- __dm_request(md, bio);
+ __split_bio(md, bio);
up_read(&md->lock);
return 0;
}
@@ -563,15 +578,15 @@ static int dm_request(request_queue_t *q
static int dm_any_congested(void *congested_data, int bdi_bits)
{
int r;
- struct mapped_device *md = congested_data;
+ struct mapped_device *md = (struct mapped_device *) congested_data;
+ struct dm_table *map = dm_get_table(md);
- read_lock(&md->maplock);
- if (md->map == NULL || test_bit(DMF_BLOCK_IO, &md->flags))
+ if (!map || test_bit(DMF_BLOCK_IO, &md->flags))
r = bdi_bits;
else
- r = dm_table_any_congested(md->map, bdi_bits);
- read_unlock(&md->maplock);
+ r = dm_table_any_congested(map, bdi_bits);
+ dm_table_put(map);
return r;
}
@@ -646,7 +661,7 @@ static struct mapped_device *alloc_dev(u
memset(md, 0, sizeof(*md));
init_rwsem(&md->lock);
- rwlock_init(&md->maplock);
+ rwlock_init(&md->map_lock);
atomic_set(&md->holders, 1);
md->queue = blk_alloc_queue(GFP_KERNEL);
@@ -746,12 +761,12 @@ static int __bind(struct mapped_device *
if (size == 0)
return 0;
- write_lock(&md->maplock);
+ write_lock(&md->map_lock);
md->map = t;
- write_unlock(&md->maplock);
- dm_table_event_callback(md->map, event_callback, md);
+ write_unlock(&md->map_lock);
dm_table_get(t);
+ dm_table_event_callback(md->map, event_callback, md);
dm_table_set_restrictions(t, q);
return 0;
}
@@ -764,9 +779,9 @@ static void __unbind(struct mapped_devic
return;
dm_table_event_callback(map, NULL, NULL);
- write_lock(&md->maplock);
+ write_lock(&md->map_lock);
md->map = NULL;
- write_unlock(&md->maplock);
+ write_unlock(&md->map_lock);
dm_table_put(map);
}
@@ -803,12 +818,16 @@ void dm_get(struct mapped_device *md)
void dm_put(struct mapped_device *md)
{
+ struct dm_table *map = dm_get_table(md);
+
if (atomic_dec_and_test(&md->holders)) {
- if (!test_bit(DMF_SUSPENDED, &md->flags) && md->map)
- dm_table_suspend_targets(md->map);
+ if (!test_bit(DMF_SUSPENDED, &md->flags) && map)
+ dm_table_suspend_targets(map);
__unbind(md);
free_dev(md);
}
+
+ dm_table_put(map);
}
/*
@@ -821,7 +840,7 @@ static void __flush_deferred_io(struct m
while (c) {
n = c->bi_next;
c->bi_next = NULL;
- __dm_request(md, c);
+ __split_bio(md, c);
c = n;
}
}
@@ -859,6 +878,7 @@ int dm_swap_table(struct mapped_device *
*/
int dm_suspend(struct mapped_device *md)
{
+ struct dm_table *map;
DECLARE_WAITQUEUE(wait, current);
down_write(&md->lock);
@@ -894,8 +914,11 @@ int dm_suspend(struct mapped_device *md)
down_write(&md->lock);
remove_wait_queue(&md->wait, &wait);
set_bit(DMF_SUSPENDED, &md->flags);
- if (md->map)
- dm_table_suspend_targets(md->map);
+
+ map = dm_get_table(md);
+ if (map)
+ dm_table_suspend_targets(map);
+ dm_table_put(map);
up_write(&md->lock);
return 0;
@@ -904,22 +927,25 @@ int dm_suspend(struct mapped_device *md)
int dm_resume(struct mapped_device *md)
{
struct bio *def;
+ struct dm_table *map = dm_get_table(md);
down_write(&md->lock);
- if (!md->map ||
+ if (!map ||
!test_bit(DMF_SUSPENDED, &md->flags) ||
- !dm_table_get_size(md->map)) {
+ !dm_table_get_size(map)) {
up_write(&md->lock);
+ dm_table_put(map);
return -EINVAL;
}
- dm_table_resume_targets(md->map);
+ dm_table_resume_targets(map);
clear_bit(DMF_SUSPENDED, &md->flags);
clear_bit(DMF_BLOCK_IO, &md->flags);
def = bio_list_get(&md->deferred);
__flush_deferred_io(md, def);
up_write(&md->lock);
+ dm_table_put(map);
blk_run_queues();
@@ -971,19 +997,6 @@ struct gendisk *dm_disk(struct mapped_de
return md->disk;
}
-struct dm_table *dm_get_table(struct mapped_device *md)
-{
- struct dm_table *t;
-
- down_read(&md->lock);
- t = md->map;
- if (t)
- dm_table_get(t);
- up_read(&md->lock);
-
- return t;
-}
-
int dm_suspended(struct mapped_device *md)
{
return test_bit(DMF_SUSPENDED, &md->flags);