Btrfs: create special free space cache inode
In order to save free space cache, we need an inode to hold the data, and we
need a special item to point at the right inode for the right block group. So
first, create a special item that will point to the right inode, and the number
of extent entries we will have and the number of bitmaps we will have. We
truncate and pre-allocate space everytime to make sure it's uptodate.
This feature will be turned on as soon as you mount with -o space_cache, however
it is safe to boot into old kernels, they will just generate the cache the old
fashion way. When you boot back into a newer kernel we will notice that we
modified and not the cache and automatically discard the cache.
Signed-off-by: Josef Bacik <josef@redhat.com>
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index f488fac..05efcc7 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -23,10 +23,165 @@
#include "ctree.h"
#include "free-space-cache.h"
#include "transaction.h"
+#include "disk-io.h"
#define BITS_PER_BITMAP (PAGE_CACHE_SIZE * 8)
#define MAX_CACHE_BYTES_PER_GIG (32 * 1024)
+struct inode *lookup_free_space_inode(struct btrfs_root *root,
+ struct btrfs_block_group_cache
+ *block_group, struct btrfs_path *path)
+{
+ struct btrfs_key key;
+ struct btrfs_key location;
+ struct btrfs_disk_key disk_key;
+ struct btrfs_free_space_header *header;
+ struct extent_buffer *leaf;
+ struct inode *inode = NULL;
+ int ret;
+
+ spin_lock(&block_group->lock);
+ if (block_group->inode)
+ inode = igrab(block_group->inode);
+ spin_unlock(&block_group->lock);
+ if (inode)
+ return inode;
+
+ key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+ key.offset = block_group->key.objectid;
+ key.type = 0;
+
+ ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ if (ret > 0) {
+ btrfs_release_path(root, path);
+ return ERR_PTR(-ENOENT);
+ }
+
+ leaf = path->nodes[0];
+ header = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_free_space_header);
+ btrfs_free_space_key(leaf, header, &disk_key);
+ btrfs_disk_key_to_cpu(&location, &disk_key);
+ btrfs_release_path(root, path);
+
+ inode = btrfs_iget(root->fs_info->sb, &location, root, NULL);
+ if (!inode)
+ return ERR_PTR(-ENOENT);
+ if (IS_ERR(inode))
+ return inode;
+ if (is_bad_inode(inode)) {
+ iput(inode);
+ return ERR_PTR(-ENOENT);
+ }
+
+ spin_lock(&block_group->lock);
+ if (!root->fs_info->closing) {
+ block_group->inode = igrab(inode);
+ block_group->iref = 1;
+ }
+ spin_unlock(&block_group->lock);
+
+ return inode;
+}
+
+int create_free_space_inode(struct btrfs_root *root,
+ struct btrfs_trans_handle *trans,
+ struct btrfs_block_group_cache *block_group,
+ struct btrfs_path *path)
+{
+ struct btrfs_key key;
+ struct btrfs_disk_key disk_key;
+ struct btrfs_free_space_header *header;
+ struct btrfs_inode_item *inode_item;
+ struct extent_buffer *leaf;
+ u64 objectid;
+ int ret;
+
+ ret = btrfs_find_free_objectid(trans, root, 0, &objectid);
+ if (ret < 0)
+ return ret;
+
+ ret = btrfs_insert_empty_inode(trans, root, path, objectid);
+ if (ret)
+ return ret;
+
+ leaf = path->nodes[0];
+ inode_item = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_inode_item);
+ btrfs_item_key(leaf, &disk_key, path->slots[0]);
+ memset_extent_buffer(leaf, 0, (unsigned long)inode_item,
+ sizeof(*inode_item));
+ btrfs_set_inode_generation(leaf, inode_item, trans->transid);
+ btrfs_set_inode_size(leaf, inode_item, 0);
+ btrfs_set_inode_nbytes(leaf, inode_item, 0);
+ btrfs_set_inode_uid(leaf, inode_item, 0);
+ btrfs_set_inode_gid(leaf, inode_item, 0);
+ btrfs_set_inode_mode(leaf, inode_item, S_IFREG | 0600);
+ btrfs_set_inode_flags(leaf, inode_item, BTRFS_INODE_NOCOMPRESS |
+ BTRFS_INODE_PREALLOC | BTRFS_INODE_NODATASUM);
+ btrfs_set_inode_nlink(leaf, inode_item, 1);
+ btrfs_set_inode_transid(leaf, inode_item, trans->transid);
+ btrfs_set_inode_block_group(leaf, inode_item,
+ block_group->key.objectid);
+ btrfs_mark_buffer_dirty(leaf);
+ btrfs_release_path(root, path);
+
+ key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+ key.offset = block_group->key.objectid;
+ key.type = 0;
+
+ ret = btrfs_insert_empty_item(trans, root, path, &key,
+ sizeof(struct btrfs_free_space_header));
+ if (ret < 0) {
+ btrfs_release_path(root, path);
+ return ret;
+ }
+ leaf = path->nodes[0];
+ header = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_free_space_header);
+ memset_extent_buffer(leaf, 0, (unsigned long)header, sizeof(*header));
+ btrfs_set_free_space_key(leaf, header, &disk_key);
+ btrfs_mark_buffer_dirty(leaf);
+ btrfs_release_path(root, path);
+
+ 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;
+
+ trans->block_rsv = root->orphan_block_rsv;
+ ret = btrfs_block_rsv_check(trans, root,
+ root->orphan_block_rsv,
+ 0, 5);
+ if (ret)
+ return ret;
+
+ oldsize = i_size_read(inode);
+ btrfs_i_size_write(inode, 0);
+ truncate_pagecache(inode, oldsize, 0);
+
+ /*
+ * We don't need an orphan item because truncating the free space cache
+ * will never be split across transactions.
+ */
+ ret = btrfs_truncate_inode_items(trans, root, inode,
+ 0, BTRFS_EXTENT_DATA_KEY);
+ if (ret) {
+ WARN_ON(1);
+ return ret;
+ }
+
+ return btrfs_update_inode(trans, root, inode);
+}
+
static inline unsigned long offset_to_bit(u64 bitmap_start, u64 sectorsize,
u64 offset)
{