posix_fallocate(2) && posix_fadvise(2) are somewhat broken

[Maxim Sobolev]

Hi, while working on some unrelated feature I've noticed that at least
those two system calls are not returning proper value (-1) on error.
Instead actual errno value is returned from the syscall verbatim,
i.e. posix_fadvise() returns 22 on EINVAL. Attached patch fixes that
problem, however I am not sure if I need to assign td->td_retval[0] at all,
those two operations by design never return anything but -1 on error and 0
on success. Can someone comment on this? Thanks!
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diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index e675b09..bdb1639 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -4528,7 +4528,7 @@ sys_posix_fallocate(struct thread *td, struct posix_fallocate_args *uap)
 
 	td->td_retval[0] = kern_posix_fallocate(td, uap->fd, uap->offset,
 	    uap->len);
-	return (0);
+	return (td->td_retval[0]);
 }
 
 /*
@@ -4665,5 +4665,5 @@ sys_posix_fadvise(struct thread *td, struct posix_fadvise_args *uap)
 
 	td->td_retval[0] = kern_posix_fadvise(td, uap->fd, uap->offset,
 	    uap->len, uap->advice);
-	return (0);
+	return (td->td_retval[0]);
 }