[PATCH v3] posix_fadvise.2: NOREUSE now supported.

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POSIX_FADV_NOREUSE is now supported in Linux[1].
Updates text regarding former no op behavior. Indicates the readahead
policy and treatment of file pages read with this flag.

[1]: https://lore.kernel.org/linux-mm/20221230215252.2628425-2-yuzhao@xxxxxxxxxx/

Signed-off-by: T.J. Alumbaugh <talumbau@xxxxxxxxxx>
---
 man2/posix_fadvise.2 | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/man2/posix_fadvise.2 b/man2/posix_fadvise.2
index 57c65c810..9e562f74d 100644
--- a/man2/posix_fadvise.2
+++ b/man2/posix_fadvise.2
@@ -64,7 +64,10 @@ The specified data will be accessed only once.
 .IP
 Before Linux 2.6.18, \fBPOSIX_FADV_NOREUSE\fP had the
 same semantics as \fBPOSIX_FADV_WILLNEED\fP.
-This was probably a bug; since Linux 2.6.18, this flag is a no-op.
+This was probably a bug; from Linux 2.6.18 until Linux 6.2 this flag was
+a no-op. From Linux 6.3 and beyond, \fBPOSIX_FADV_NOREUSE\fP signals
+that the LRU algorithm can ignore access to mapped page cache marked
+by this flag. This is useful, for example, while streaming large files.
 .TP
 .B POSIX_FADV_WILLNEED
 The specified data will be accessed in the near future.
@@ -154,6 +157,7 @@ in POSIX.1-2001 TC1.
 Under Linux, \fBPOSIX_FADV_NORMAL\fP sets the readahead window to the
 default size for the backing device; \fBPOSIX_FADV_SEQUENTIAL\fP doubles
 this size, and \fBPOSIX_FADV_RANDOM\fP disables file readahead entirely.
+\fBPOSIX_FADV_NOREUSE\fP does not modify the readahead window size.
 These changes affect the entire file, not just the specified region
 (but other open file handles to the same file are unaffected).
 .PP
-- 
2.40.0.rc1.284.g88254d51c5-goog




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