[PATCH man-pages v2 2/4] madvise.2: document reliable probe for advice support

[Zach OKeefe <zokeefe@google.com>]

From: Zach O'Keefe <zokeefe@google.com>

EINVAL is an overloaded error code for madvise(2) and it's not clear
under what context it means "advice is not valid" vs another error.

Explicitly document that madvise(0, 0, advice) can reliably be used to
probe for kernel support for "advice", returning zero iff "advice" is
supported by the kernel.

Signed-off-by: Zach O'Keefe <zokeefe@google.com>
---
 man2/madvise.2 | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/man2/madvise.2 b/man2/madvise.2
index 64f788ace..df3413cc8 100644
--- a/man2/madvise.2
+++ b/man2/madvise.2
@@ -790,6 +790,11 @@ that are not mapped, the Linux version of
 ignores them and applies the call to the rest (but returns
 .B ENOMEM
 from the system call, as it should).
+.PP
+.IR madvise(0,\ 0,\ advice)
+will return zero iff
+.I advice
+is supported by the kernel and can be relied on to probe for support.
 .\" .SH HISTORY
 .\" The
 .\" .BR madvise ()
-- 
2.38.0.413.g74048e4d9e-goog