vfs: micro-optimize acl_permission_check()

It's a hot function, and we're better off not mixing types in the mask
calculations.  The compiler just ends up mixing 16-bit and 32-bit
operations, for no good reason.

So do everything in 'unsigned int' rather than mixing 'unsigned int'
masking with a 'umode_t' (16-bit) mode variable.

This, together with the parent commit (47a150ed: "Cache user_ns in
struct cred") makes acl_permission_check() much nicer.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namei.c

@@ -179,7 +179,7 @@ EXPORT_SYMBOL(putname);
 static int acl_permission_check(struct inode *inode, int mask, unsigned int flags,
 		int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
 {
-	umode_t			mode = inode->i_mode;
+	unsigned int mode = inode->i_mode;
 
 	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;