VFS: repack LOOKUP_ bit flags.

The LOOKUP_ bits are not in order, which can make it awkward when adding
new bits.  Two bits have recently been added to the end which makes them
look like "scoping flags", but in fact they aren't.

Also LOOKUP_PARENT is described as "internal use only" but is used in
fs/nfs/

This patch:
 - Moves these three flags into the "pathwalk mode" section
 - changes all bits to use the BIT(n) macro
 - Allocates bits in order leaving gaps between the sections,
   and documents those gaps.

Signed-off-by: NeilBrown <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>

Author: neilbrown

include/linux/namei.h

@@ -18,35 +18,36 @@ enum { MAX_NESTED_LINKS = 8 };
 enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
 
 /* pathwalk mode */
-#define LOOKUP_FOLLOW		0x0001	/* follow links at the end */
-#define LOOKUP_DIRECTORY	0x0002	/* require a directory */
-#define LOOKUP_AUTOMOUNT	0x0004  /* force terminal automount */
-#define LOOKUP_EMPTY		0x4000	/* accept empty path [user_... only] */
-#define LOOKUP_DOWN		0x8000	/* follow mounts in the starting point */
-#define LOOKUP_MOUNTPOINT	0x0080	/* follow mounts in the end */
-
-#define LOOKUP_REVAL		0x0020	/* tell ->d_revalidate() to trust no cache */
-#define LOOKUP_RCU		0x0040	/* RCU pathwalk mode; semi-internal */
+#define LOOKUP_FOLLOW		BIT(0)	/* follow links at the end */
+#define LOOKUP_DIRECTORY	BIT(1)	/* require a directory */
+#define LOOKUP_AUTOMOUNT	BIT(2)  /* force terminal automount */
+#define LOOKUP_EMPTY		BIT(3)	/* accept empty path [user_... only] */
+#define LOOKUP_LINKAT_EMPTY	BIT(4) /* Linkat request with empty path. */
+#define LOOKUP_DOWN		BIT(5)	/* follow mounts in the starting point */
+#define LOOKUP_MOUNTPOINT	BIT(6)	/* follow mounts in the end */
+#define LOOKUP_REVAL		BIT(7)	/* tell ->d_revalidate() to trust no cache */
+#define LOOKUP_RCU		BIT(8)	/* RCU pathwalk mode; semi-internal */
+#define LOOKUP_CACHED		BIT(9) /* Only do cached lookup */
+#define LOOKUP_PARENT		BIT(10)	/* Looking up final parent in path */
+/* 5 spare bits for pathwalk */
 
 /* These tell filesystem methods that we are dealing with the final component... */
-#define LOOKUP_OPEN		0x0100	/* ... in open */
-#define LOOKUP_CREATE		0x0200	/* ... in object creation */
-#define LOOKUP_EXCL		0x0400	/* ... in exclusive creation */
-#define LOOKUP_RENAME_TARGET	0x0800	/* ... in destination of rename() */
+#define LOOKUP_OPEN		BIT(16)	/* ... in open */
+#define LOOKUP_CREATE		BIT(17)	/* ... in object creation */
+#define LOOKUP_EXCL		BIT(18)	/* ... in target must not exist */
+#define LOOKUP_RENAME_TARGET	BIT(19)	/* ... in destination of rename() */
 
-/* internal use only */
-#define LOOKUP_PARENT		0x0010
+/* 4 spare bits for intent */
 
 /* Scoping flags for lookup. */
-#define LOOKUP_NO_SYMLINKS	0x010000 /* No symlink crossing. */
-#define LOOKUP_NO_MAGICLINKS	0x020000 /* No nd_jump_link() crossing. */
-#define LOOKUP_NO_XDEV		0x040000 /* No mountpoint crossing. */
-#define LOOKUP_BENEATH		0x080000 /* No escaping from starting point. */
-#define LOOKUP_IN_ROOT		0x100000 /* Treat dirfd as fs root. */
-#define LOOKUP_CACHED		0x200000 /* Only do cached lookup */
-#define LOOKUP_LINKAT_EMPTY	0x400000 /* Linkat request with empty path. */
+#define LOOKUP_NO_SYMLINKS	BIT(24) /* No symlink crossing. */
+#define LOOKUP_NO_MAGICLINKS	BIT(25) /* No nd_jump_link() crossing. */
+#define LOOKUP_NO_XDEV		BIT(26) /* No mountpoint crossing. */
+#define LOOKUP_BENEATH		BIT(27) /* No escaping from starting point. */
+#define LOOKUP_IN_ROOT		BIT(28) /* Treat dirfd as fs root. */
 /* LOOKUP_* flags which do scope-related checks based on the dirfd. */
 #define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT)
+/* 3 spare bits for scoping */
 
 extern int path_pts(struct path *path);