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[v7,6/8] Btrfs: introduce uuid-tree-gen field

Message ID 3c4e3a51a75827038244c3f23a7f65537e17aa4d.1372866277.git.sbehrens@giantdisaster.de (mailing list archive)
State Superseded, archived
Headers show

Commit Message

Stefan Behrens July 3, 2013, 5:14 p.m. UTC 
In order to be able to detect the case that a filesystem is mounted
with an old kernel, add a uuid-tree-gen field like the free space
cache is doing it. It is part of the super block and written with
each commit. Old kernels do not know this field and don't update it.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
---
 fs/btrfs/ctree.h       | 5 ++++-
 fs/btrfs/transaction.c | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)
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Patch

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8523538..9bf4d42 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -481,9 +481,10 @@  struct btrfs_super_block {
 	char label[BTRFS_LABEL_SIZE];
 
 	__le64 cache_generation;
+	__le64 uuid_tree_generation;
 
 	/* future expansion */
-	__le64 reserved[31];
+	__le64 reserved[30];
 	u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
 	struct btrfs_root_backup super_roots[BTRFS_NUM_BACKUP_ROOTS];
 } __attribute__ ((__packed__));
@@ -2849,6 +2850,8 @@  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);
+BTRFS_SETGET_STACK_FUNCS(super_uuid_tree_generation, struct btrfs_super_block,
+			 uuid_tree_generation, 64);
 
 static inline int btrfs_super_csum_size(struct btrfs_super_block *s)
 {
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 4f2fe5e..dbc2ebf 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1380,6 +1380,7 @@  static void update_super_roots(struct btrfs_root *root)
 	super->root_level = root_item->level;
 	if (btrfs_test_opt(root, SPACE_CACHE))
 		super->cache_generation = root_item->generation;
+	super->uuid_tree_generation = root_item->generation;
 }
 
 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)