vfs: add fileattr ops

There's a substantial amount of boilerplate in filesystems handling
FS_IOC_[GS]ETFLAGS/ FS_IOC_FS[GS]ETXATTR ioctls.

Also due to userspace buffers being involved in the ioctl API this is
difficult to stack, as shown by overlayfs issues related to these ioctls.

Introduce a new internal API named "fileattr" (fsxattr can be confused with
xattr, xflags is inappropriate, since this is more than just flags).

There's significant overlap between flags and xflags and this API handles
the conversions automatically, so filesystems may choose which one to use.

In ->fileattr_get() a hint is provided to the filesystem whether flags or
xattr are being requested by userspace, but in this series this hint is
ignored by all filesystems, since generating all the attributes is cheap.

If a filesystem doesn't implemement the fileattr API, just fall back to
f_op->ioctl().  When all filesystems are converted, the fallback can be
removed.

32bit compat ioctls are now handled by the generic code as well.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
new file mode 100644
index 000000000000..9e37e063ac69
--- /dev/null
+++ b/include/linux/fileattr.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_FILEATTR_H
+#define _LINUX_FILEATTR_H
+
+/* Flags shared betwen flags/xflags */
+#define FS_COMMON_FL \
+	(FS_SYNC_FL | FS_IMMUTABLE_FL | FS_APPEND_FL | \
+	 FS_NODUMP_FL |	FS_NOATIME_FL | FS_DAX_FL | \
+	 FS_PROJINHERIT_FL)
+
+#define FS_XFLAG_COMMON \
+	(FS_XFLAG_SYNC | FS_XFLAG_IMMUTABLE | FS_XFLAG_APPEND | \
+	 FS_XFLAG_NODUMP | FS_XFLAG_NOATIME | FS_XFLAG_DAX | \
+	 FS_XFLAG_PROJINHERIT)
+
+/*
+ * Merged interface for miscellaneous file attributes.  'flags' originates from
+ * ext* and 'fsx_flags' from xfs.  There's some overlap between the two, which
+ * is handled by the VFS helpers, so filesystems are free to implement just one
+ * or both of these sub-interfaces.
+ */
+struct fileattr {
+	u32	flags;		/* flags (FS_IOC_GETFLAGS/FS_IOC_SETFLAGS) */
+	/* struct fsxattr: */
+	u32	fsx_xflags;	/* xflags field value (get/set) */
+	u32	fsx_extsize;	/* extsize field value (get/set)*/
+	u32	fsx_nextents;	/* nextents field value (get)	*/
+	u32	fsx_projid;	/* project identifier (get/set) */
+	u32	fsx_cowextsize;	/* CoW extsize field value (get/set)*/
+	/* selectors: */
+	bool	flags_valid:1;
+	bool	fsx_valid:1;
+};
+
+int copy_fsxattr_to_user(const struct fileattr *fa, struct fsxattr __user *ufa);
+
+void fileattr_fill_xflags(struct fileattr *fa, u32 xflags);
+void fileattr_fill_flags(struct fileattr *fa, u32 flags);
+
+/**
+ * fileattr_has_fsx - check for extended flags/attributes
+ * @fa:		fileattr pointer
+ *
+ * Return: true if any attributes are present that are not represented in
+ * ->flags.
+ */
+static inline bool fileattr_has_fsx(const struct fileattr *fa)
+{
+	return fa->fsx_valid &&
+		((fa->fsx_xflags & ~FS_XFLAG_COMMON) || fa->fsx_extsize != 0 ||
+		 fa->fsx_projid != 0 ||	fa->fsx_cowextsize != 0);
+}
+
+int vfs_fileattr_get(struct dentry *dentry, struct fileattr *fa);
+int vfs_fileattr_set(struct user_namespace *mnt_userns, struct dentry *dentry,
+		     struct fileattr *fa);
+
+#endif /* _LINUX_FILEATTR_H */