Btrfs: don't use global block reservation for inode cache truncation

It is very likely that there are lots of subvolumes/snapshots in the filesystem,
so if we use global block reservation to do inode cache truncation, we may hog
all the free space that is reserved in global rsv. So it is better that we do
the free space reservation for inode cache truncation by ourselves.

Cc: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

5 files changed, 34 insertions, 22 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index c4c94b30c729..162a66bfbffd 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3106,6 +3106,11 @@ again:
 	WARN_ON(ret);
 
 	if (i_size_read(inode) > 0) {
+		ret = btrfs_check_trunc_cache_free_space(root,
+					&root->fs_info->global_block_rsv);
+		if (ret)
+			goto out_put;
+
 		ret = btrfs_truncate_free_space_cache(root, trans, path,
 						      inode);
 		if (ret)
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 6a8bb9c79674..e53009657f0e 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -197,30 +197,32 @@ int create_free_space_inode(struct btrfs_root *root,
 					 block_group->key.objectid);
 }
 
-int btrfs_truncate_free_space_cache(struct btrfs_root *root,
-				    struct btrfs_trans_handle *trans,
-				    struct btrfs_path *path,
-				    struct inode *inode)
+int btrfs_check_trunc_cache_free_space(struct btrfs_root *root,
+				       struct btrfs_block_rsv *rsv)
 {
-	struct btrfs_block_rsv *rsv;
 	u64 needed_bytes;
-	loff_t oldsize;
-	int ret = 0;
-
-	rsv = trans->block_rsv;
-	trans->block_rsv = &root->fs_info->global_block_rsv;
+	int ret;
 
 	/* 1 for slack space, 1 for updating the inode */
 	needed_bytes = btrfs_calc_trunc_metadata_size(root, 1) +
 		btrfs_calc_trans_metadata_size(root, 1);
 
-	spin_lock(&trans->block_rsv->lock);
-	if (trans->block_rsv->reserved < needed_bytes) {
-		spin_unlock(&trans->block_rsv->lock);
-		trans->block_rsv = rsv;
-		return -ENOSPC;
-	}
-	spin_unlock(&trans->block_rsv->lock);
+	spin_lock(&rsv->lock);
+	if (rsv->reserved < needed_bytes)
+		ret = -ENOSPC;
+	else
+		ret = 0;
+	spin_unlock(&rsv->lock);
+	return 0;
+}
+
+int btrfs_truncate_free_space_cache(struct btrfs_root *root,
+				    struct btrfs_trans_handle *trans,
+				    struct btrfs_path *path,
+				    struct inode *inode)
+{
+	loff_t oldsize;
+	int ret = 0;
 
 	oldsize = i_size_read(inode);
 	btrfs_i_size_write(inode, 0);
@@ -232,9 +234,7 @@ int btrfs_truncate_free_space_cache(struct btrfs_root *root,
 	 */
 	ret = btrfs_truncate_inode_items(trans, root, inode,
 					 0, BTRFS_EXTENT_DATA_KEY);
-
 	if (ret) {
-		trans->block_rsv = rsv;
 		btrfs_abort_transaction(trans, root, ret);
 		return ret;
 	}
@@ -242,7 +242,6 @@ int btrfs_truncate_free_space_cache(struct btrfs_root *root,
 	ret = btrfs_update_inode(trans, root, inode);
 	if (ret)
 		btrfs_abort_transaction(trans, root, ret);
-	trans->block_rsv = rsv;
 
 	return ret;
 }
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 4dc17d8809c7..8b7f19f44961 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -54,6 +54,8 @@ int create_free_space_inode(struct btrfs_root *root,
 			    struct btrfs_block_group_cache *block_group,
 			    struct btrfs_path *path);
 
+int btrfs_check_trunc_cache_free_space(struct btrfs_root *root,
+				       struct btrfs_block_rsv *rsv);
 int btrfs_truncate_free_space_cache(struct btrfs_root *root,
 				    struct btrfs_trans_handle *trans,
 				    struct btrfs_path *path,
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 9818d4a3f829..2c66ddbbe670 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -429,11 +429,12 @@ int btrfs_save_ino_cache(struct btrfs_root *root,
 	num_bytes = trans->bytes_reserved;
 	/*
 	 * 1 item for inode item insertion if need
-	 * 3 items for inode item update (in the worst case)
+	 * 4 items for inode item update (in the worst case)
+	 * 1 items for slack space if we need do truncation
 	 * 1 item for free space object
 	 * 3 items for pre-allocation
 	 */
-	trans->bytes_reserved = btrfs_calc_trans_metadata_size(root, 8);
+	trans->bytes_reserved = btrfs_calc_trans_metadata_size(root, 10);
 	ret = btrfs_block_rsv_add(root, trans->block_rsv,
 				  trans->bytes_reserved,
 				  BTRFS_RESERVE_NO_FLUSH);
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 5c5b8bb44ee5..395b82031a42 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3350,6 +3350,11 @@ static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
 	}
 
 truncate:
+	ret = btrfs_check_trunc_cache_free_space(root,
+						 &fs_info->global_block_rsv);
+	if (ret)
+		goto out;
+
 	path = btrfs_alloc_path();
 	if (!path) {
 		ret = -ENOMEM;