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From:   Chengen Du <chengen.du@canonical.com>
To:     steved@redhat.com
Cc:     linux-nfs@vger.kernel.org, Chengen Du <chengen.du@canonical.com>
Subject: [PATCH] nfs(5): adding new mount option 'fasc'
Date:   Thu, 11 May 2023 21:10:18 +0800
Message-Id: <20230511131018.61266-1-chengen.du@canonical.com>
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Add an option that triggers the clearing of the file
access cache as soon as the cache timestamp becomes
older than the user's login time.

Signed-off-by: Chengen Du <chengen.du@canonical.com>
---
 utils/mount/nfs.man | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/utils/mount/nfs.man b/utils/mount/nfs.man
index 7a410422..68514fbd 100644
--- a/utils/mount/nfs.man
+++ b/utils/mount/nfs.man
@@ -574,6 +574,7 @@ The
 .B sloppy
 option is an alternative to specifying
 .BR mount.nfs " -s " option.
+
 .TP 1.5i
 .BI xprtsec= policy
 Specifies the use of transport layer security to protect NFS network
@@ -607,6 +608,19 @@ option is not specified,
 the default behavior depends on the kernel,
 but is usually equivalent to
 .BR "xprtsec=none" .
+.TP 1.5i
+.B fasc
+Triggers the clearing of the file access cache as soon as the cache 
+timestamp becomes older than the user's login time. It is supported 
+in kernels 6.4 and later.
+.IP
+NFS servers often refresh their users' group membership at their 
+own cadence, which means the NFS client's file access cache can 
+become stale if the user's group membership changes on the server 
+after they've logged in on the client. To align with the principles 
+of the POSIX design, which only refreshes the user's supplementary 
+group information upon login, the mechanism uses the user's login 
+time to determine whether the file access cache needs to be refreshed.
 .SS "Options for NFS versions 2 and 3 only"
 Use these options, along with the options in the above subsection,
 for NFS versions 2 and 3 only.
-- 
2.39.2