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btrfs: remove btrfs_dev_replace::read_locks

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This member seems to be copied from the extent_buffer locking scheme and
is at least used to assert that the read lock/unlock is properly nested.
In some way. While the _inc/_dec are called inside the read lock
section, the asserts are both inside and outside, so the ordering is not
guaranteed and we can see read/inc/dec ordered in any way
(theoretically).

A missing call of btrfs_dev_replace_clear_lock_blocking could cause
unexpected read_locks count, so this at least looks like a valid
assertion, but this will become unnecessary with later updates.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2018-08-24 17:32:29 +02:00
parent f556faa46e
commit 3280f87457
3 changed files with 0 additions and 7 deletions
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1
fs/btrfs/ctree.h
View File

@ -361,7 +361,6 @@ struct btrfs_dev_replace {
struct mutex lock_finishing_cancel_unmount; struct mutex lock_finishing_cancel_unmount;
rwlock_t lock; rwlock_t lock;
atomic_t read_locks;
atomic_t blocking_readers; atomic_t blocking_readers;
wait_queue_head_t read_lock_wq; wait_queue_head_t read_lock_wq;

5
fs/btrfs/dev-replace.c
View File

@ -964,13 +964,10 @@ int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
void btrfs_dev_replace_read_lock(struct btrfs_dev_replace *dev_replace) void btrfs_dev_replace_read_lock(struct btrfs_dev_replace *dev_replace)
{ {
read_lock(&dev_replace->lock); read_lock(&dev_replace->lock);
atomic_inc(&dev_replace->read_locks);
} }
void btrfs_dev_replace_read_unlock(struct btrfs_dev_replace *dev_replace) void btrfs_dev_replace_read_unlock(struct btrfs_dev_replace *dev_replace)
{ {
ASSERT(atomic_read(&dev_replace->read_locks) > 0);
atomic_dec(&dev_replace->read_locks);
read_unlock(&dev_replace->lock); read_unlock(&dev_replace->lock);
} }
@ -997,7 +994,6 @@ void btrfs_dev_replace_set_lock_blocking(
struct btrfs_dev_replace *dev_replace) struct btrfs_dev_replace *dev_replace)
{ {
/* only set blocking for read lock */ /* only set blocking for read lock */
ASSERT(atomic_read(&dev_replace->read_locks) > 0);
atomic_inc(&dev_replace->blocking_readers); atomic_inc(&dev_replace->blocking_readers);
read_unlock(&dev_replace->lock); read_unlock(&dev_replace->lock);
} }
@ -1007,7 +1003,6 @@ void btrfs_dev_replace_clear_lock_blocking(
struct btrfs_dev_replace *dev_replace) struct btrfs_dev_replace *dev_replace)
{ {
/* only set blocking for read lock */ /* only set blocking for read lock */
ASSERT(atomic_read(&dev_replace->read_locks) > 0);
ASSERT(atomic_read(&dev_replace->blocking_readers) > 0); ASSERT(atomic_read(&dev_replace->blocking_readers) > 0);
read_lock(&dev_replace->lock); read_lock(&dev_replace->lock);
/* Barrier implied by atomic_dec_and_test */ /* Barrier implied by atomic_dec_and_test */

1
fs/btrfs/disk-io.c
View File

@ -2155,7 +2155,6 @@ static void btrfs_init_dev_replace_locks(struct btrfs_fs_info *fs_info)
{ {
mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount); mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount);
rwlock_init(&fs_info->dev_replace.lock); rwlock_init(&fs_info->dev_replace.lock);
atomic_set(&fs_info->dev_replace.read_locks, 0);
atomic_set(&fs_info->dev_replace.blocking_readers, 0); atomic_set(&fs_info->dev_replace.blocking_readers, 0);
init_waitqueue_head(&fs_info->replace_wait); init_waitqueue_head(&fs_info->replace_wait);
init_waitqueue_head(&fs_info->dev_replace.read_lock_wq); init_waitqueue_head(&fs_info->dev_replace.read_lock_wq);