Btrfs: save balance parameters to disk

Introduce a new btree objectid for storing balance item.  The reason is
to be able to resume restriper after a crash with the same parameters.
Balance item has a very high objectid and goes into tree of tree roots.

The key for the new item is as follows:

	[ BTRFS_BALANCE_OBJECTID ; BTRFS_BALANCE_ITEM_KEY ; 0 ]

Older kernels simply ignore it so it's safe to mount with an older
kernel and then go back to the newer one.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 132 insertions, 1 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1e7aea60da2b..9997a59e4f58 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -86,6 +86,9 @@ struct btrfs_ordered_sum;
 /* holds checksums of all the data extents */
 #define BTRFS_CSUM_TREE_OBJECTID 7ULL
 
+/* for storing balance parameters in the root tree */
+#define BTRFS_BALANCE_OBJECTID -4ULL
+
 /* orhpan objectid for tracking unlinked/truncated files */
 #define BTRFS_ORPHAN_OBJECTID -5ULL
 
@@ -692,6 +695,54 @@ struct btrfs_root_ref {
         __le16 name_len;
 } __attribute__ ((__packed__));
 
+struct btrfs_disk_balance_args {
+        /*
+         * profiles to operate on, single is denoted by
+         * BTRFS_AVAIL_ALLOC_BIT_SINGLE
+         */
+        __le64 profiles;
+
+        /* usage filter */
+        __le64 usage;
+
+        /* devid filter */
+        __le64 devid;
+
+        /* devid subset filter [pstart..pend) */
+        __le64 pstart;
+        __le64 pend;
+
+        /* btrfs virtual address space subset filter [vstart..vend) */
+        __le64 vstart;
+        __le64 vend;
+
+        /*
+         * profile to convert to, single is denoted by
+         * BTRFS_AVAIL_ALLOC_BIT_SINGLE
+         */
+        __le64 target;
+
+        /* BTRFS_BALANCE_ARGS_* */
+        __le64 flags;
+
+        __le64 unused[8];
+} __attribute__ ((__packed__));
+
+/*
+ * store balance parameters to disk so that balance can be properly
+ * resumed after crash or unmount
+ */
+struct btrfs_balance_item {
+        /* BTRFS_BALANCE_* */
+        __le64 flags;
+
+        struct btrfs_disk_balance_args data;
+        struct btrfs_disk_balance_args meta;
+        struct btrfs_disk_balance_args sys;
+
+        __le64 unused[4];
+} __attribute__ ((__packed__));
+
 #define BTRFS_FILE_EXTENT_INLINE 0
 #define BTRFS_FILE_EXTENT_REG 1
 #define BTRFS_FILE_EXTENT_PREALLOC 2
@@ -1409,6 +1460,8 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_DEV_ITEM_KEY      216
 #define BTRFS_CHUNK_ITEM_KEY    228
 
+#define BTRFS_BALANCE_ITEM_KEY  248
+
 /*
  * string items are for debugging.  They just store a short string of
  * data in the FS
@@ -2103,8 +2156,86 @@ BTRFS_SETGET_STACK_FUNCS(backup_bytes_used, struct btrfs_root_backup,
 BTRFS_SETGET_STACK_FUNCS(backup_num_devices, struct btrfs_root_backup,
                    num_devices, 64);
 
-/* struct btrfs_super_block */
+/* struct btrfs_balance_item */
+BTRFS_SETGET_FUNCS(balance_flags, struct btrfs_balance_item, flags, 64);
+
+static inline void btrfs_balance_data(struct extent_buffer *eb,
+                                      struct btrfs_balance_item *bi,
+                                      struct btrfs_disk_balance_args *ba)
+{
+        read_eb_member(eb, bi, struct btrfs_balance_item, data, ba);
+}
+
+static inline void btrfs_set_balance_data(struct extent_buffer *eb,
+                                          struct btrfs_balance_item *bi,
+                                          struct btrfs_disk_balance_args *ba)
+{
+        write_eb_member(eb, bi, struct btrfs_balance_item, data, ba);
+}
+
+static inline void btrfs_balance_meta(struct extent_buffer *eb,
+                                      struct btrfs_balance_item *bi,
+                                      struct btrfs_disk_balance_args *ba)
+{
+        read_eb_member(eb, bi, struct btrfs_balance_item, meta, ba);
+}
+
+static inline void btrfs_set_balance_meta(struct extent_buffer *eb,
+                                          struct btrfs_balance_item *bi,
+                                          struct btrfs_disk_balance_args *ba)
+{
+        write_eb_member(eb, bi, struct btrfs_balance_item, meta, ba);
+}
+
+static inline void btrfs_balance_sys(struct extent_buffer *eb,
+                                     struct btrfs_balance_item *bi,
+                                     struct btrfs_disk_balance_args *ba)
+{
+        read_eb_member(eb, bi, struct btrfs_balance_item, sys, ba);
+}
+
+static inline void btrfs_set_balance_sys(struct extent_buffer *eb,
+                                         struct btrfs_balance_item *bi,
+                                         struct btrfs_disk_balance_args *ba)
+{
+        write_eb_member(eb, bi, struct btrfs_balance_item, sys, ba);
+}
 
+static inline void
+btrfs_disk_balance_args_to_cpu(struct btrfs_balance_args *cpu,
+                               struct btrfs_disk_balance_args *disk)
+{
+        memset(cpu, 0, sizeof(*cpu));
+
+        cpu->profiles = le64_to_cpu(disk->profiles);
+        cpu->usage = le64_to_cpu(disk->usage);
+        cpu->devid = le64_to_cpu(disk->devid);
+        cpu->pstart = le64_to_cpu(disk->pstart);
+        cpu->pend = le64_to_cpu(disk->pend);
+        cpu->vstart = le64_to_cpu(disk->vstart);
+        cpu->vend = le64_to_cpu(disk->vend);
+        cpu->target = le64_to_cpu(disk->target);
+        cpu->flags = le64_to_cpu(disk->flags);
+}
+
+static inline void
+btrfs_cpu_balance_args_to_disk(struct btrfs_disk_balance_args *disk,
+                               struct btrfs_balance_args *cpu)
+{
+        memset(disk, 0, sizeof(*disk));
+
+        disk->profiles = cpu_to_le64(cpu->profiles);
+        disk->usage = cpu_to_le64(cpu->usage);
+        disk->devid = cpu_to_le64(cpu->devid);
+        disk->pstart = cpu_to_le64(cpu->pstart);
+        disk->pend = cpu_to_le64(cpu->pend);
+        disk->vstart = cpu_to_le64(cpu->vstart);
+        disk->vend = cpu_to_le64(cpu->vend);
+        disk->target = cpu_to_le64(cpu->target);
+        disk->flags = cpu_to_le64(cpu->flags);
+}
+
+/* struct btrfs_super_block */
 BTRFS_SETGET_STACK_FUNCS(super_bytenr, struct btrfs_super_block, bytenr, 64);
 BTRFS_SETGET_STACK_FUNCS(super_flags, struct btrfs_super_block, flags, 64);
 BTRFS_SETGET_STACK_FUNCS(super_generation, struct btrfs_super_block,