[PATCH v2 4/4] btrfs: support default mount options

[Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>]

Make space to save default mount options in super block.
Parse saved default mount options first and then parse mount options given
when the file system is mounted.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
---
 fs/btrfs/ctree.h |    7 ++++++-
 fs/btrfs/super.c |   16 ++++++++++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0d195b5..eea6bd0 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -461,8 +461,11 @@ struct btrfs_super_block {
 
 	__le64 cache_generation;
 
+	/* default mount options */
+	__le64 default_mount_opt;
+
 	/* 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__));
@@ -2581,6 +2584,8 @@ 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_default_mount_opt, struct btrfs_super_block,
+			 default_mount_opt, 64);
 
 static inline int btrfs_super_csum_size(struct btrfs_super_block *s)
 {
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index d51aaee..1cadf0e 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -567,13 +567,25 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 	struct btrfs_fs_info *info = root->fs_info;
 	substring_t args[MAX_OPT_ARGS];
 	char *p, *orig = NULL;
-	u64 cache_gen;
+	u64 cache_gen, default_opt;
 	int ret = 0;
 
-	cache_gen = btrfs_super_cache_generation(root->fs_info->super_copy);
+	cache_gen = btrfs_super_cache_generation(info->super_copy);
 	if (cache_gen)
 		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
 
+	default_opt = btrfs_super_default_mount_opt(info->super_copy);
+	if (default_opt) {
+		int token;
+		for (token = 0; token < Opt_err; token++) {
+			if (default_opt & (1ul << token)) {
+				ret = __btrfs_parse_options(info, token, args);
+				if (ret)
+					return ret;
+			}
+		}
+	}
+
 	if (!options)
 		goto out;
 
-- 
1.7.7.6