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>

1 files changed, 68 insertions, 6 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index eaf286abad1..46f52e1bead 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -99,6 +99,9 @@ struct btrfs_ordered_sum;
  */
 #define BTRFS_EXTENT_CSUM_OBJECTID -10ULL
 
+/* For storing free space cache */
+#define BTRFS_FREE_SPACE_OBJECTID -11ULL
+
 /* dummy objectid represents multiple objectids */
 #define BTRFS_MULTIPLE_OBJECTIDS -255ULL
 
@@ -265,6 +268,22 @@ struct btrfs_chunk {
         /* additional stripes go here */
 } __attribute__ ((__packed__));
 
+#define BTRFS_FREE_SPACE_EXTENT 1
+#define BTRFS_FREE_SPACE_BITMAP 2
+
+struct btrfs_free_space_entry {
+        __le64 offset;
+        __le64 bytes;
+        u8 type;
+} __attribute__ ((__packed__));
+
+struct btrfs_free_space_header {
+        struct btrfs_disk_key location;
+        __le64 generation;
+        __le64 num_entries;
+        __le64 num_bitmaps;
+} __attribute__ ((__packed__));
+
 static inline unsigned long btrfs_chunk_item_size(int num_stripes)
 {
         BUG_ON(num_stripes == 0);
@@ -365,8 +384,10 @@ struct btrfs_super_block {
 
         char label[BTRFS_LABEL_SIZE];
 
+        __le64 cache_generation;
+
         /* future expansion */
-        __le64 reserved[32];
+        __le64 reserved[31];
         u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
 } __attribute__ ((__packed__));
 
@@ -375,12 +396,12 @@ struct btrfs_super_block {
  * ones specified below then we will fail to mount
  */
 #define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF    (1ULL << 0)
-#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL   (2ULL << 0)
+#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL   (1ULL << 1)
 
 #define BTRFS_FEATURE_COMPAT_SUPP               0ULL
 #define BTRFS_FEATURE_COMPAT_RO_SUPP            0ULL
-#define BTRFS_FEATURE_INCOMPAT_SUPP             \
-        (BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF | \
+#define BTRFS_FEATURE_INCOMPAT_SUPP                     \
+        (BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF |         \
          BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL)
 
 /*
@@ -750,6 +771,14 @@ enum btrfs_caching_type {
         BTRFS_CACHE_FINISHED    = 2,
 };
 
+enum btrfs_disk_cache_state {
+        BTRFS_DC_WRITTEN        = 0,
+        BTRFS_DC_ERROR          = 1,
+        BTRFS_DC_CLEAR          = 2,
+        BTRFS_DC_SETUP          = 3,
+        BTRFS_DC_NEED_WRITE     = 4,
+};
+
 struct btrfs_caching_control {
         struct list_head list;
         struct mutex mutex;
@@ -763,6 +792,7 @@ struct btrfs_block_group_cache {
         struct btrfs_key key;
         struct btrfs_block_group_item item;
         struct btrfs_fs_info *fs_info;
+        struct inode *inode;
         spinlock_t lock;
         u64 pinned;
         u64 reserved;
@@ -773,8 +803,11 @@ struct btrfs_block_group_cache {
         int extents_thresh;
         int free_extents;
         int total_bitmaps;
-        int ro;
-        int dirty;
+        int ro:1;
+        int dirty:1;
+        int iref:1;
+
+        int disk_cache_state;
 
         /* cache tracking stuff */
         int cached;
@@ -1192,6 +1225,7 @@ struct btrfs_root {
 #define BTRFS_MOUNT_NOSSD               (1 << 9)
 #define BTRFS_MOUNT_DISCARD             (1 << 10)
 #define BTRFS_MOUNT_FORCE_COMPRESS      (1 << 11)
+#define BTRFS_MOUNT_SPACE_CACHE         (1 << 12)
 
 #define btrfs_clear_opt(o, opt)         ((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)           ((o) |= BTRFS_MOUNT_##opt)
@@ -1665,6 +1699,27 @@ static inline void btrfs_set_dir_item_key(struct extent_buffer *eb,
         write_eb_member(eb, item, struct btrfs_dir_item, location, key);
 }
 
+BTRFS_SETGET_FUNCS(free_space_entries, struct btrfs_free_space_header,
+                   num_entries, 64);
+BTRFS_SETGET_FUNCS(free_space_bitmaps, struct btrfs_free_space_header,
+                   num_bitmaps, 64);
+BTRFS_SETGET_FUNCS(free_space_generation, struct btrfs_free_space_header,
+                   generation, 64);
+
+static inline void btrfs_free_space_key(struct extent_buffer *eb,
+                                        struct btrfs_free_space_header *h,
+                                        struct btrfs_disk_key *key)
+{
+        read_eb_member(eb, h, struct btrfs_free_space_header, location, key);
+}
+
+static inline void btrfs_set_free_space_key(struct extent_buffer *eb,
+                                            struct btrfs_free_space_header *h,
+                                            struct btrfs_disk_key *key)
+{
+        write_eb_member(eb, h, struct btrfs_free_space_header, location, key);
+}
+
 /* struct btrfs_disk_key */
 BTRFS_SETGET_STACK_FUNCS(disk_key_objectid, struct btrfs_disk_key,
                          objectid, 64);
@@ -1876,6 +1931,8 @@ BTRFS_SETGET_STACK_FUNCS(super_incompat_flags, struct btrfs_super_block,
                          incompat_flags, 64);
 BTRFS_SETGET_STACK_FUNCS(super_csum_type, struct btrfs_super_block,
                          csum_type, 16);
+BTRFS_SETGET_STACK_FUNCS(super_cache_generation, struct btrfs_super_block,
+                         cache_generation, 64);
 
 static inline int btrfs_super_csum_size(struct btrfs_super_block *s)
 {
@@ -2115,6 +2172,7 @@ int btrfs_set_block_group_ro(struct btrfs_root *root,
                              struct btrfs_block_group_cache *cache);
 int btrfs_set_block_group_rw(struct btrfs_root *root,
                              struct btrfs_block_group_cache *cache);
+void btrfs_put_block_group_cache(struct btrfs_fs_info *info);
 /* ctree.c */
 int btrfs_bin_search(struct extent_buffer *eb, struct btrfs_key *key,
                      int level, int *slot);
@@ -2426,6 +2484,10 @@ void btrfs_run_delayed_iputs(struct btrfs_root *root);
 int btrfs_prealloc_file_range(struct inode *inode, int mode,
                               u64 start, u64 num_bytes, u64 min_size,
                               loff_t actual_len, u64 *alloc_hint);
+int btrfs_prealloc_file_range_trans(struct inode *inode,
+                                    struct btrfs_trans_handle *trans, int mode,
+                                    u64 start, u64 num_bytes, u64 min_size,
+                                    loff_t actual_len, u64 *alloc_hint);
 extern const struct dentry_operations btrfs_dentry_operations;
 
 /* ioctl.c */