[PATCH 1/2] btrfs: add compat flag functions

[Mark Harmstone <mark@harmstone.com>]

struct btrfs_super_block contains a field compat_flags that has never
been used, intended for informational flags that don't prevent a
filesystem from being mounted read-write if the kernel doesn't
understand them.

Add the support functions needed for these, following the pattern of
compat_ro_flags and incompat_flags.

Signed-off-by: Mark Harmstone <mark@harmstone.com>
---
 fs/btrfs/fs.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/fs.h | 13 +++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/fs/btrfs/fs.c b/fs/btrfs/fs.c
index feb0a2faa837..1d7293a575cf 100644
--- a/fs/btrfs/fs.c
+++ b/fs/btrfs/fs.c
@@ -273,3 +273,49 @@ void __btrfs_clear_fs_compat_ro(struct btrfs_fs_info *fs_info, u64 flag,
 		set_bit(BTRFS_FS_FEATURE_CHANGED, &fs_info->flags);
 	}
 }
+
+void __btrfs_set_fs_compat(struct btrfs_fs_info *fs_info, u64 flag,
+			   const char *name)
+{
+	struct btrfs_super_block *disk_super;
+	u64 features;
+
+	disk_super = fs_info->super_copy;
+	features = btrfs_super_compat_flags(disk_super);
+	if (!(features & flag)) {
+		spin_lock(&fs_info->super_lock);
+		features = btrfs_super_compat_flags(disk_super);
+		if (!(features & flag)) {
+			features |= flag;
+			btrfs_set_super_compat_flags(disk_super, features);
+			btrfs_info(fs_info,
+				"setting compat feature flag for %s (0x%llx)",
+				name, flag);
+		}
+		spin_unlock(&fs_info->super_lock);
+		set_bit(BTRFS_FS_FEATURE_CHANGED, &fs_info->flags);
+	}
+}
+
+void __btrfs_clear_fs_compat(struct btrfs_fs_info *fs_info, u64 flag,
+			     const char *name)
+{
+	struct btrfs_super_block *disk_super;
+	u64 features;
+
+	disk_super = fs_info->super_copy;
+	features = btrfs_super_compat_flags(disk_super);
+	if (features & flag) {
+		spin_lock(&fs_info->super_lock);
+		features = btrfs_super_compat_flags(disk_super);
+		if (features & flag) {
+			features &= ~flag;
+			btrfs_set_super_compat_flags(disk_super, features);
+			btrfs_info(fs_info,
+				"clearing compat feature flag for %s (0x%llx)",
+				name, flag);
+		}
+		spin_unlock(&fs_info->super_lock);
+		set_bit(BTRFS_FS_FEATURE_CHANGED, &fs_info->flags);
+	}
+}
diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index 814bbc9417d2..3a8b4aba12d2 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -1053,6 +1053,10 @@ void __btrfs_set_fs_compat_ro(struct btrfs_fs_info *fs_info, u64 flag,
 			      const char *name);
 void __btrfs_clear_fs_compat_ro(struct btrfs_fs_info *fs_info, u64 flag,
 				const char *name);
+void __btrfs_set_fs_compat(struct btrfs_fs_info *fs_info, u64 flag,
+			   const char *name);
+void __btrfs_clear_fs_compat(struct btrfs_fs_info *fs_info, u64 flag,
+			     const char *name);
 
 #define __btrfs_fs_incompat(fs_info, flags)				\
 	(!!(btrfs_super_incompat_flags((fs_info)->super_copy) & (flags)))
@@ -1060,6 +1064,9 @@ void __btrfs_clear_fs_compat_ro(struct btrfs_fs_info *fs_info, u64 flag,
 #define __btrfs_fs_compat_ro(fs_info, flags)				\
 	(!!(btrfs_super_compat_ro_flags((fs_info)->super_copy) & (flags)))
 
+#define __btrfs_fs_compat(fs_info, flags)				\
+	(!!(btrfs_super_compat_flags((fs_info)->super_copy) & (flags)))
+
 #define btrfs_set_fs_incompat(__fs_info, opt)				\
 	__btrfs_set_fs_incompat((__fs_info), BTRFS_FEATURE_INCOMPAT_##opt, #opt)
 
@@ -1078,6 +1085,12 @@ void __btrfs_clear_fs_compat_ro(struct btrfs_fs_info *fs_info, u64 flag,
 #define btrfs_fs_compat_ro(fs_info, opt)				\
 	__btrfs_fs_compat_ro((fs_info), BTRFS_FEATURE_COMPAT_RO_##opt)
 
+#define btrfs_fs_compat(fs_info, opt)				\
+	__btrfs_fs_compat((fs_info), BTRFS_FEATURE_COMPAT_##opt)
+
+#define btrfs_set_fs_compat(__fs_info, opt)				\
+	__btrfs_set_fs_compat((__fs_info), BTRFS_FEATURE_COMPAT_##opt, #opt)
+
 #define btrfs_clear_opt(o, opt)		((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)		((o) |= BTRFS_MOUNT_##opt)
 #define btrfs_raw_test_opt(o, opt)	((o) & BTRFS_MOUNT_##opt)
-- 
2.49.1