From d06094d4469258a722c94f8bb5bc25b5c9711718 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nikola=20Forr=C3=B3?= <nforro@redhat.com>
Date: Fri, 9 Jul 2021 18:34:34 +0200
Subject: [PATCH 1/2] statx.2: add STATX_ATTR_DAX

---
 man-pages/man2/statx.2 | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/man-pages/man2/statx.2 b/man-pages/man2/statx.2
index bb04455..686edc8 100644
--- a/man-pages/man2/statx.2
+++ b/man-pages/man2/statx.2
@@ -462,6 +462,36 @@ See
 .TP
 .B STATX_ATTR_ENCRYPTED
 A key is required for the file to be encrypted by the filesystem.
+.TP
+.BR STATX_ATTR_DAX " (since Linux 5.8)"
+The file is in the DAX (cpu direct access) state.
+DAX state attempts to
+minimize software cache effects for both I/O and memory mappings of this file.
+It requires a file system which has been configured to support DAX.
+.IP
+DAX generally assumes all accesses are via CPU load / store instructions
+which can minimize overhead for small accesses,
+but may adversely affect CPU utilization for large transfers.
+.IP
+File I/O is done directly to/from user-space buffers and memory mapped I/O may
+be performed with direct memory mappings that bypass the kernel page cache.
+.IP
+While the DAX property tends to result in data being transferred synchronously,
+it does not give the same guarantees as the
+.B O_SYNC
+flag (see
+.BR open (2)),
+where data and the necessary metadata are transferred together.
+.IP
+A DAX file may support being mapped with the
+.B MAP_SYNC
+flag, which enables a
+program to use CPU cache flush instructions to persist CPU store operations
+without an explicit
+.BR fsync (2).
+See
+.BR mmap (2)
+for more information.
 .SH RETURN VALUE
 On success, zero is returned.
 On error, \-1 is returned, and
-- 
2.31.1