[PATCH] f2fs: add ioctl to expose current features

[Jaegeuk Kim <jaegeuk@kernel.org>]

This patch adds an ioctl to provide feature information to user.
For exapmle, SQLite can use this ioctl to detect whether f2fs support atomic
write or not.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/f2fs.h |  2 ++
 fs/f2fs/file.c | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e06d4e4b4579..5c46a462b56e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -112,6 +112,7 @@ struct f2fs_mount_info {
 
 #define F2FS_FEATURE_ENCRYPT	0x0001
 #define F2FS_FEATURE_BLKZONED	0x0002
+#define F2FS_FEATURE_ATOMIC_WRITE 0x0004
 
 #define F2FS_HAS_FEATURE(sb, mask)					\
 	((F2FS_SB(sb)->raw_super->feature & cpu_to_le32(mask)) != 0)
@@ -308,6 +309,7 @@ static inline bool __has_cursum_space(struct f2fs_journal *journal,
 						struct f2fs_flush_device)
 #define F2FS_IOC_GARBAGE_COLLECT_RANGE	_IOW(F2FS_IOCTL_MAGIC, 11,	\
 						struct f2fs_gc_range)
+#define	F2FS_IOC_GET_FEATURES		_IOR(F2FS_IOCTL_MAGIC, 12, __u32)
 
 #define F2FS_IOC_SET_ENCRYPTION_POLICY	FS_IOC_SET_ENCRYPTION_POLICY
 #define F2FS_IOC_GET_ENCRYPTION_POLICY	FS_IOC_GET_ENCRYPTION_POLICY
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 2706130c261b..0e07b5b18cfa 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2384,6 +2384,16 @@ static int f2fs_ioc_flush_device(struct file *filp, unsigned long arg)
 	return ret;
 }
 
+static int f2fs_ioc_get_features(struct file *filp, unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	u32 sb_feature = le32_to_cpu(F2FS_I_SB(inode)->raw_super->feature);
+
+	/* Must validate to set it with SQLite behavior in Android. */
+	sb_feature |= F2FS_FEATURE_ATOMIC_WRITE;
+
+	return put_user(sb_feature, (u32 __user *)arg);
+}
 
 long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
@@ -2426,6 +2436,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return f2fs_ioc_move_range(filp, arg);
 	case F2FS_IOC_FLUSH_DEVICE:
 		return f2fs_ioc_flush_device(filp, arg);
+	case F2FS_IOC_GET_FEATURES:
+		return f2fs_ioc_get_features(filp, arg);
 	default:
 		return -ENOTTY;
 	}
@@ -2491,6 +2503,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case F2FS_IOC_DEFRAGMENT:
 	case F2FS_IOC_MOVE_RANGE:
 	case F2FS_IOC_FLUSH_DEVICE:
+	case F2FS_IOC_GET_FEATURES:
 		break;
 	default:
 		return -ENOIOCTLCMD;
-- 
2.13.0.rc1.294.g07d810a77f-goog