[PATCH] Btrfs: don't reserve metadata when we're using the delalloc reserve

[Josef Bacik <josef@redhat.com>]

There are a bunch of places where we do btrfs_join_transaction(root, 1), but
really we set the block_rsv to the delalloc reserve because our metadata was
reserved at delalloc time.  This means we don't need to reserve space at all,
and can just join the transaction and go.  This patch also fixes a few places
where we weren't actually setting the block_rsv to the delalloc reserve.
Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
---
 fs/btrfs/inode.c |   27 +++++++++++++++++----------
 1 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c4b914e..e9bda50 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -420,7 +420,7 @@ again:
 		}
 	}
 	if (start == 0) {
-		trans = btrfs_join_transaction(root, 1);
+		trans = btrfs_join_transaction(root, 0);
 		BUG_ON(IS_ERR(trans));
 		btrfs_set_trans_block_group(trans, inode);
 		trans->block_rsv = &root->fs_info->delalloc_block_rsv;
@@ -617,8 +617,9 @@ retry:
 			    async_extent->start + async_extent->ram_size - 1,
 			    GFP_NOFS);
 
-		trans = btrfs_join_transaction(root, 1);
+		trans = btrfs_join_transaction(root, 0);
 		BUG_ON(IS_ERR(trans));
+		trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 		ret = btrfs_reserve_extent(trans, root,
 					   async_extent->compressed_size,
 					   async_extent->compressed_size,
@@ -778,7 +779,12 @@ static noinline int cow_file_range(struct inode *inode,
 	int ret = 0;
 
 	BUG_ON(root == root->fs_info->tree_root);
-	trans = btrfs_join_transaction(root, 1);
+
+	/*
+	 * Our metadata reservations should have been taken care of in the
+	 * delalloc stuff, so we don't need to reserve space here.
+	 */
+	trans = btrfs_join_transaction(root, 0);
 	BUG_ON(IS_ERR(trans));
 	btrfs_set_trans_block_group(trans, inode);
 	trans->block_rsv = &root->fs_info->delalloc_block_rsv;
@@ -1054,11 +1060,12 @@ static noinline int run_delalloc_nocow(struct inode *inode,
 	BUG_ON(!path);
 	if (root == root->fs_info->tree_root) {
 		nolock = true;
-		trans = btrfs_join_transaction_nolock(root, 1);
+		trans = btrfs_join_transaction_nolock(root, 0);
 	} else {
-		trans = btrfs_join_transaction(root, 1);
+		trans = btrfs_join_transaction(root, 0);
 	}
 	BUG_ON(IS_ERR(trans));
+	trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 
 	cow_start = (u64)-1;
 	cur_offset = start;
@@ -1715,9 +1722,9 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
 		ret = btrfs_ordered_update_i_size(inode, 0, ordered_extent);
 		if (!ret) {
 			if (nolock)
-				trans = btrfs_join_transaction_nolock(root, 1);
+				trans = btrfs_join_transaction_nolock(root, 0);
 			else
-				trans = btrfs_join_transaction(root, 1);
+				trans = btrfs_join_transaction(root, 0);
 			BUG_ON(IS_ERR(trans));
 			btrfs_set_trans_block_group(trans, inode);
 			trans->block_rsv = &root->fs_info->delalloc_block_rsv;
@@ -1732,9 +1739,9 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
 			 0, &cached_state, GFP_NOFS);
 
 	if (nolock)
-		trans = btrfs_join_transaction_nolock(root, 1);
+		trans = btrfs_join_transaction_nolock(root, 0);
 	else
-		trans = btrfs_join_transaction(root, 1);
+		trans = btrfs_join_transaction(root, 0);
 	BUG_ON(IS_ERR(trans));
 	btrfs_set_trans_block_group(trans, inode);
 	trans->block_rsv = &root->fs_info->delalloc_block_rsv;
@@ -5839,7 +5846,7 @@ again:
 
 	BUG_ON(!ordered);
 
-	trans = btrfs_join_transaction(root, 1);
+	trans = btrfs_join_transaction(root, 0);
 	if (IS_ERR(trans)) {
 		err = -ENOMEM;
 		goto out;
-- 
1.7.2.3