Merge pull request ceph#58596 from batrick/superuser-doc

doc: clarify superuser note for ceph-fuse

Reviewed-by: Zac Dover <[email protected]>

Author: zdover23

doc/cephfs/mount-prerequisites.rst

@@ -1,12 +1,11 @@
 Mount CephFS: Prerequisites
 ===========================
 
-You can use CephFS by mounting it to your local filesystem or by using
-:ref:`cephfs-shell <cephfs-shell>`. Mounting CephFS requires superuser
-privileges to trim dentries by issuing a remount of itself. CephFS can be
-mounted `using kernel`_ as well as `using FUSE`_. Both have their own
-advantages. Read the following section to understand more about both of these
-ways to mount CephFS.
+You can use CephFS by mounting the file system on a machine or by using
+:ref:`cephfs-shell <cephfs-shell>`. A system mount can be performed using `the
+kernel driver`_ as well as `the FUSE driver`_. Both have their own advantages
+and disadvantages. Read the following section to understand more about both of
+these ways to mount CephFS.
 
 For Windows CephFS mounts, please check the `ceph-dokan`_ page.
 
@@ -70,6 +69,6 @@ Ceph MON resides.
 
 .. _Client Authentication: ../client-auth
 .. _cephfs-shell: ..cephfs-shell
-.. _using kernel: ../mount-using-kernel-driver
-.. _using FUSE: ../mount-using-fuse
+.. _the kernel driver: ../mount-using-kernel-driver
+.. _the FUSE driver: ../mount-using-fuse
 .. _ceph-dokan: ../ceph-dokan

doc/cephfs/mount-using-fuse.rst

@@ -12,8 +12,11 @@ Prerequisites
 Go through the prerequisites required by both, kernel as well as FUSE mounts,
 in `Mount CephFS: Prerequisites`_ page.
 
-.. note:: Mounting CephFS using FUSE requires superuser privileges to trim dentries
-   by issuing a remount of itself.
+.. note:: Mounting CephFS using FUSE requires superuser privileges (sudo/root).
+          The libfuse interface does not provide a mechanism to trim cache entries in the
+          kernel so a remount (``mount(2)``) system call is required to force the kernel
+          to drop the cached metadata. ``ceph-fuse`` issues these remount system calls
+          periodically in response to cache pressure in the MDS or due to metadata cache revocations.
 
 Synopsis
 ========