Btrfs: Fixes for 2.6.18 enterprise kernels

2.6.18 seems to get caught in an infinite loop when
cancel_rearming_delayed_workqueue is called more than once, so this switches
to cancel_delayed_work, which is arguably more correct.

Also, balance_dirty_pages can run into problems with 2.6.18 based kernels
because it doesn't have the per-bdi dirty limits.  This avoids calling
balance_dirty_pages on the btree inode unless there is actually something
to balance, which is a good optimization in general.

Finally there's a compile fix for ordered-data.h
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/disk-io.c

@@ -1548,6 +1548,7 @@ int close_ctree(struct btrfs_root *root)
 	btrfs_commit_transaction(trans, root);
 	ret = btrfs_write_and_wait_transaction(NULL, root);
 	BUG_ON(ret);
+
 	write_ctree_super(NULL, root);
 	mutex_unlock(&fs_info->fs_mutex);
 
@@ -1583,17 +1584,17 @@ int close_ctree(struct btrfs_root *root)
 	extent_io_tree_empty_lru(&fs_info->extent_ins);
 	extent_io_tree_empty_lru(&BTRFS_I(fs_info->btree_inode)->io_tree);
 
-	flush_workqueue(end_io_workqueue);
 	flush_workqueue(async_submit_workqueue);
+	flush_workqueue(end_io_workqueue);
 
 	truncate_inode_pages(fs_info->btree_inode->i_mapping, 0);
 
-	flush_workqueue(end_io_workqueue);
-	destroy_workqueue(end_io_workqueue);
-
 	flush_workqueue(async_submit_workqueue);
 	destroy_workqueue(async_submit_workqueue);
 
+	flush_workqueue(end_io_workqueue);
+	destroy_workqueue(end_io_workqueue);
+
 	iput(fs_info->btree_inode);
 #if 0
 	while(!list_empty(&fs_info->hashers)) {
@@ -1663,8 +1664,21 @@ void btrfs_throttle(struct btrfs_root *root)
 
 void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
 {
+	struct extent_io_tree *tree;
+	u64 num_dirty;
+	u64 start = 0;
+	unsigned long thresh = 16 * 1024 * 1024;
+	tree = &BTRFS_I(root->fs_info->btree_inode)->io_tree;
+
+	if (current_is_pdflush())
+		return;
+
+	num_dirty = count_range_bits(tree, &start, (u64)-1,
+				     thresh, EXTENT_DIRTY);
+	if (num_dirty > thresh) {
 		balance_dirty_pages_ratelimited_nr(
 				   root->fs_info->btree_inode->i_mapping, 1);
+	}
 }
 
 void btrfs_set_buffer_defrag(struct extent_buffer *buf)

fs/btrfs/ordered-data.c

@@ -18,6 +18,7 @@
 
 #include <linux/gfp.h>
 #include <linux/slab.h>
+#include <linux/blkdev.h>
 #include "ctree.h"
 #include "transaction.h"
 #include "btrfs_inode.h"

fs/btrfs/transaction.c

@@ -814,6 +814,9 @@ void btrfs_transaction_cleaner(struct work_struct *work)
 	int ret;
 
 	mutex_lock(&root->fs_info->fs_mutex);
+	if (root->fs_info->closing)
+		goto out;
+
 	mutex_lock(&root->fs_info->trans_mutex);
 	cur = root->fs_info->running_transaction;
 	if (!cur) {
@@ -838,12 +841,13 @@ void btrfs_transaction_cleaner(struct work_struct *work)
 
 void btrfs_transaction_queue_work(struct btrfs_root *root, int delay)
 {
+	if (!root->fs_info->closing)
 		queue_delayed_work(trans_wq, &root->fs_info->trans_work, delay);
 }
 
 void btrfs_transaction_flush_work(struct btrfs_root *root)
 {
-	cancel_rearming_delayed_workqueue(trans_wq, &root->fs_info->trans_work);
+	cancel_delayed_work(&root->fs_info->trans_work);
 	flush_workqueue(trans_wq);
 }