From 276e680d192a67d222fcea51af37b056feffb665 Mon Sep 17 00:00:00 2001 From: Yan Zheng Date: Thu, 30 Jul 2009 09:40:40 -0400 Subject: Btrfs: preserve commit_root for async caching The async block group caching code uses the commit_root pointer to get a stable version of the extent allocation tree for scanning. This copy of the tree root isn't going to change and it significantly reduces the complexity of the scanning code. During a commit, we have a loop where we update the extent allocation tree root. We need to loop because updating the root pointer in the tree of tree roots may allocate blocks which may change the extent allocation tree. Right now the commit_root pointer is changed inside this loop. It is more correct to change the commit_root pointer only after all the looping is done. Signed-off-by: Yan Zheng Signed-off-by: Chris Mason --- fs/btrfs/ctree.h | 4 +--- fs/btrfs/disk-io.c | 2 +- fs/btrfs/extent-tree.c | 6 +++--- fs/btrfs/transaction.c | 12 +++++++++--- 4 files changed, 14 insertions(+), 10 deletions(-) (limited to 'fs/btrfs') diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 17ad92c29cf..38eeb6c49c8 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -827,6 +827,7 @@ struct btrfs_fs_info { struct mutex drop_mutex; struct mutex volume_mutex; struct mutex tree_reloc_mutex; + struct rw_semaphore extent_commit_sem; /* * this protects the ordered operations list only while we are @@ -961,9 +962,6 @@ struct btrfs_root { /* the node lock is held while changing the node pointer */ spinlock_t node_lock; - /* taken when updating the commit root */ - struct rw_semaphore commit_root_sem; - struct extent_buffer *commit_root; struct btrfs_root *log_root; struct btrfs_root *reloc_root; diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 3a9b8875988..3cf4cfa575c 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -907,7 +907,6 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize, spin_lock_init(&root->inode_lock); mutex_init(&root->objectid_mutex); mutex_init(&root->log_mutex); - init_rwsem(&root->commit_root_sem); init_waitqueue_head(&root->log_writer_wait); init_waitqueue_head(&root->log_commit_wait[0]); init_waitqueue_head(&root->log_commit_wait[1]); @@ -1624,6 +1623,7 @@ struct btrfs_root *open_ctree(struct super_block *sb, mutex_init(&fs_info->cleaner_mutex); mutex_init(&fs_info->volume_mutex); mutex_init(&fs_info->tree_reloc_mutex); + init_rwsem(&fs_info->extent_commit_sem); btrfs_init_free_cluster(&fs_info->meta_alloc_cluster); btrfs_init_free_cluster(&fs_info->data_alloc_cluster); diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index fadf69a2764..2fe21fa7491 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -267,7 +267,7 @@ static int caching_kthread(void *data) last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET); again: /* need to make sure the commit_root doesn't disappear */ - down_read(&fs_info->extent_root->commit_root_sem); + down_read(&fs_info->extent_commit_sem); /* * We don't want to deadlock with somebody trying to allocate a new @@ -304,7 +304,7 @@ again: if (need_resched()) { btrfs_release_path(fs_info->extent_root, path); - up_read(&fs_info->extent_root->commit_root_sem); + up_read(&fs_info->extent_commit_sem); cond_resched(); goto again; } @@ -345,7 +345,7 @@ next: err: btrfs_free_path(path); - up_read(&fs_info->extent_root->commit_root_sem); + up_read(&fs_info->extent_commit_sem); atomic_dec(&block_group->space_info->caching_threads); wake_up(&block_group->caching_q); diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index e51d2bc532f..de48e4ec808 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -42,10 +42,8 @@ static noinline void put_transaction(struct btrfs_transaction *transaction) static noinline void switch_commit_root(struct btrfs_root *root) { - down_write(&root->commit_root_sem); free_extent_buffer(root->commit_root); root->commit_root = btrfs_root_node(root); - up_write(&root->commit_root_sem); } /* @@ -466,7 +464,10 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans, ret = btrfs_write_dirty_block_groups(trans, root); BUG_ON(ret); } - switch_commit_root(root); + + if (root != root->fs_info->extent_root) + switch_commit_root(root); + return 0; } @@ -499,6 +500,11 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans, update_cowonly_root(trans, root); } + + down_write(&fs_info->extent_commit_sem); + switch_commit_root(fs_info->extent_root); + up_write(&fs_info->extent_commit_sem); + return 0; } -- cgit v1.2.3-70-g09d2 From f36f3042eae238bdaefe7c79310afe573bfc3622 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Thu, 30 Jul 2009 10:04:48 -0400 Subject: Btrfs: be more polite in the async caching threads The semaphore used by the async caching threads can prevent a transaction commit, which can make the FS appear to stall. This releases the semaphore more often when a transaction commit is in progress. Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 5 +++-- fs/btrfs/transaction.c | 10 ++++++++++ fs/btrfs/transaction.h | 1 + 3 files changed, 14 insertions(+), 2 deletions(-) (limited to 'fs/btrfs') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 2fe21fa7491..dc84daee6bc 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -302,10 +302,11 @@ again: else if (ret) break; - if (need_resched()) { + if (need_resched() || + btrfs_transaction_in_commit(fs_info)) { btrfs_release_path(fs_info->extent_root, path); up_read(&fs_info->extent_commit_sem); - cond_resched(); + schedule_timeout(1); goto again; } diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index de48e4ec808..cdbb5022da5 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -857,6 +857,16 @@ static void update_super_roots(struct btrfs_root *root) super->root_level = root_item->level; } +int btrfs_transaction_in_commit(struct btrfs_fs_info *info) +{ + int ret = 0; + spin_lock(&info->new_trans_lock); + if (info->running_transaction) + ret = info->running_transaction->in_commit; + spin_unlock(&info->new_trans_lock); + return ret; +} + int btrfs_commit_transaction(struct btrfs_trans_handle *trans, struct btrfs_root *root) { diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h index 961c3ee5a2e..663c6740491 100644 --- a/fs/btrfs/transaction.h +++ b/fs/btrfs/transaction.h @@ -107,4 +107,5 @@ int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans, struct btrfs_root *root); int btrfs_write_and_wait_marked_extents(struct btrfs_root *root, struct extent_io_tree *dirty_pages); +int btrfs_transaction_in_commit(struct btrfs_fs_info *info); #endif -- cgit v1.2.3-70-g09d2