IO#advise should not raise Errno::ENOSYS

As it is just a hint the kernel is free to ignore,
IO#advise already succeeds when posix_fadvise is not
available build time at all.  Following that, if posix_fadvise
was available at build time but not implemented in the running
kernel, we should also ignore it.

* io.c (do_io_advise): do not raise on ENOSYS
* test/ruby/test_io.rb (test_advise): do not skip on Errno::ENOSYS
  (test_advise_pipe): ditto
  [ruby-core:72066] [Feature #11806]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53047 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/io.c b/io.c
index d5bd2fc84f..c8c13f85ea 100644
--- a/io.c
+++ b/io.c
@@ -8586,7 +8586,7 @@ do_io_advise(rb_io_t *fptr, VALUE advice, off_t offset, off_t len)
     ias.len    = len;
 
     rv = (int)rb_thread_io_blocking_region(io_advise_internal, &ias, fptr->fd);
-    if (rv) {
+    if (rv && rv != ENOSYS) {
 	/* posix_fadvise(2) doesn't set errno. On success it returns 0; otherwise
 	   it returns the error code. */
 	VALUE message = rb_sprintf("%"PRIsVALUE" "