linux-kernel - [PATCH v2] Documentation/dax: Update description of DAX policy changing

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Message-ID: <20210106015000.5263-1-lihao2018.fnst@cn.fujitsu.com>
Date:   Wed, 6 Jan 2021 09:50:00 +0800
From:   Hao Li <lihao2018.fnst@...fujitsu.com>
To:     <corbet@....net>
CC:     <davem@...emloft.net>, <gregkh@...uxfoundation.org>,
        <alexander.deucher@....com>, <mchehab+huawei@...nel.org>,
        <lee.jones@...aro.org>, <ira.weiny@...el.com>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <lihao2018.fnst@...fujitsu.com>
Subject: [PATCH v2] Documentation/dax: Update description of DAX policy changing

After commit 77573fa310d9 ("fs: Kill DCACHE_DONTCACHE dentry even if
DCACHE_REFERENCED is set"), changes to DAX policy will take effect
as soon as all references to this file are gone.

Update the documentation accordingly.

Signed-off-by: Hao Li <lihao2018.fnst@...fujitsu.com>
---
Changes in v2:
  * simplify sentences and fix style problems.

 Documentation/filesystems/dax.txt | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt
index 8fdb78f3c6c9..e03c20564f3a 100644
--- a/Documentation/filesystems/dax.txt
+++ b/Documentation/filesystems/dax.txt
@@ -83,20 +83,9 @@ Summary
        directories.  This has runtime constraints and limitations that are
        described in 6) below.
 
- 6. When changing the S_DAX policy via toggling the persistent FS_XFLAG_DAX flag,
-    the change in behaviour for existing regular files may not occur
-    immediately.  If the change must take effect immediately, the administrator
-    needs to:
-
-    a) stop the application so there are no active references to the data set
-       the policy change will affect
-
-    b) evict the data set from kernel caches so it will be re-instantiated when
-       the application is restarted. This can be achieved by:
-
-       i. drop-caches
-       ii. a filesystem unmount and mount cycle
-       iii. a system reboot
+ 6. When changing the S_DAX policy via toggling the persistent FS_XFLAG_DAX
+    flag, the change to existing regular files won't take effect until the
+    files are closed by all processes.
 
 
 Details
-- 
2.29.2