From 129827e3001fd1e6892a0629b48f9c7c91cbb8b6 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Thu, 5 Apr 2018 01:29:24 +0200 Subject: [PATCH] btrfs: dev-replace: swich locking to rw semaphore This is the first part of removing the custom locking and waiting scheme used for device replace. It was probably copied from extent buffer locking, but there's nothing that would require more than is provided by the common locking primitives. The rw spinlock protects waiting tasks counter in case of incompatible locks and the waitqueue. Same as rw semaphore. This patch only switches the locking primitive, for better bisectability. There should be no functional change other than the overhead of the locking and potential sleeping instead of spinning when the lock is contended. Signed-off-by: David Sterba --- fs/btrfs/ctree.h | 2 +- fs/btrfs/dev-replace.c | 12 ++++++------ fs/btrfs/disk-io.c | 2 +- 3 files changed, 8 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 81cbbb2..b4f9712 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -378,7 +378,7 @@ struct btrfs_dev_replace { struct btrfs_device *tgtdev; struct mutex lock_finishing_cancel_unmount; - rwlock_t lock; + struct rw_semaphore rwsem; atomic_t blocking_readers; wait_queue_head_t read_lock_wq; diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 3b272ff..316a292 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -1002,12 +1002,12 @@ int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace) void btrfs_dev_replace_read_lock(struct btrfs_dev_replace *dev_replace) { - read_lock(&dev_replace->lock); + down_read(&dev_replace->rwsem); } void btrfs_dev_replace_read_unlock(struct btrfs_dev_replace *dev_replace) { - read_unlock(&dev_replace->lock); + up_read(&dev_replace->rwsem); } void btrfs_dev_replace_write_lock(struct btrfs_dev_replace *dev_replace) @@ -1015,16 +1015,16 @@ void btrfs_dev_replace_write_lock(struct btrfs_dev_replace *dev_replace) again: wait_event(dev_replace->read_lock_wq, atomic_read(&dev_replace->blocking_readers) == 0); - write_lock(&dev_replace->lock); + down_write(&dev_replace->rwsem); if (atomic_read(&dev_replace->blocking_readers)) { - write_unlock(&dev_replace->lock); + up_write(&dev_replace->rwsem); goto again; } } void btrfs_dev_replace_write_unlock(struct btrfs_dev_replace *dev_replace) { - write_unlock(&dev_replace->lock); + up_write(&dev_replace->rwsem); } /* inc blocking cnt and release read lock */ @@ -1033,7 +1033,7 @@ void btrfs_dev_replace_set_lock_blocking( { /* only set blocking for read lock */ atomic_inc(&dev_replace->blocking_readers); - read_unlock(&dev_replace->lock); + up_read(&dev_replace->rwsem); } void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 14d355d..eca66ac 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2141,7 +2141,7 @@ static void btrfs_init_btree_inode(struct btrfs_fs_info *fs_info) static void btrfs_init_dev_replace_locks(struct btrfs_fs_info *fs_info) { mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount); - rwlock_init(&fs_info->dev_replace.lock); + init_rwsem(&fs_info->dev_replace.rwsem); atomic_set(&fs_info->dev_replace.blocking_readers, 0); init_waitqueue_head(&fs_info->dev_replace.replace_wait); init_waitqueue_head(&fs_info->dev_replace.read_lock_wq); -- 2.7.4