[PATCH] readv.2: document RWF_NOWAIT

[Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>]

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 man2/readv.2 | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/man2/readv.2 b/man2/readv.2
index 831cf6260..21d82849e 100644
--- a/man2/readv.2
+++ b/man2/readv.2
@@ -232,6 +232,25 @@ This flag is meaningful only for
 .BR pwritev2 (),
 and its effect applies only to the data range written by the system call.
 .\" commit e864f39569f4092c2b2bc72c773b6e486c7e3bd9
+.TP
+.BR RWF_NOWAIT " (since Linux 4.14)"
+Dot not wait for data when it cannot be instantly retreived.  If this flag
+is specified the
+.BR preadv2 ()
+system call will return instantly when it would have to read data from
+the backing storage or wait for a lock.  Instead it will return -1 and set
+.I errno
+to
+.BR EAGAIN
+if no data could be read, or return less bytes than requested if some data
+could be read.
+This flag is meaningful only for
+.BR preadv2 ()
+at the moment.
+.\" commit 3239d834847627b6634a4139cf1dc58f6f137a46
+.\" commit 91f9943e1c7b6638f27312d03fe71fcc67b23571
+
+
 .SH RETURN VALUE
 On success,
 .BR readv (),
-- 
2.14.2

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