ext4: add a new ioctl EXT4_IOC_GETSTATE

The new ioctl EXT4_IOC_GETSTATE returns some of the dynamic state of
an ext4 inode for debugging purposes.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -651,6 +651,7 @@ enum {
 #define EXT4_IOC_GET_ENCRYPTION_POLICY	FS_IOC_GET_ENCRYPTION_POLICY
 /* ioctl codes 19--39 are reserved for fscrypt */
 #define EXT4_IOC_CLEAR_ES_CACHE		_IO('f', 40)
+#define EXT4_IOC_GETSTATE		_IOW('f', 41, __u32)
 
 #define EXT4_IOC_FSGETXATTR		FS_IOC_FSGETXATTR
 #define EXT4_IOC_FSSETXATTR		FS_IOC_FSSETXATTR
@@ -664,6 +665,16 @@ enum {
 #define EXT4_GOING_FLAGS_LOGFLUSH		0x1	/* flush log but not data */
 #define EXT4_GOING_FLAGS_NOLOGFLUSH		0x2	/* don't flush log nor data */
 
+/*
+ * Flags returned by EXT4_IOC_GETSTATE
+ *
+ * We only expose to userspace a subset of the state flags in
+ * i_state_flags
+ */
+#define EXT4_STATE_FLAG_EXT_PRECACHED	0x00000001
+#define EXT4_STATE_FLAG_NEW		0x00000002
+#define EXT4_STATE_FLAG_NEWENTRY	0x00000004
+#define EXT4_STATE_FLAG_DA_ALLOC_CLOSE	0x00000008
 
 #if defined(__KERNEL__) && defined(CONFIG_COMPAT)
 /*

fs/ext4/ioctl.c

@@ -1123,6 +1123,22 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return 0;
 	}
 
+	case EXT4_IOC_GETSTATE:
+	{
+		__u32	state = 0;
+
+		if (ext4_test_inode_state(inode, EXT4_STATE_EXT_PRECACHED))
+			state |= EXT4_STATE_FLAG_EXT_PRECACHED;
+		if (ext4_test_inode_state(inode, EXT4_STATE_NEW))
+			state |= EXT4_STATE_FLAG_NEW;
+		if (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
+			state |= EXT4_STATE_FLAG_NEWENTRY;
+		if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE))
+			state |= EXT4_STATE_FLAG_DA_ALLOC_CLOSE;
+
+		return put_user(state, (__u32 __user *) arg);
+	}
+
 	case EXT4_IOC_FSGETXATTR:
 	{
 		struct fsxattr fa;
@@ -1242,6 +1258,7 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case EXT4_IOC_SHUTDOWN:
 	case FS_IOC_GETFSMAP:
 	case EXT4_IOC_CLEAR_ES_CACHE:
+	case EXT4_IOC_GETSTATE:
 		break;
 	default:
 		return -ENOIOCTLCMD;