Let's clarify from where we take idmapping of each type: - caller - filesystem - mount Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Christian Brauner <brauner@xxxxxxxxxx> Cc: linux-fsdevel@xxxxxxxxxxxxxxx Cc: linux-doc@xxxxxxxxxxxxxxx Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx> --- v2: - fixed https://lore.kernel.org/oe-kbuild-all/202306252253.qxHG1txo-lkp@xxxxxxxxx/ --- Documentation/filesystems/idmappings.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/filesystems/idmappings.rst b/Documentation/filesystems/idmappings.rst index ad6d21640576..f3d168c9f0b9 100644 --- a/Documentation/filesystems/idmappings.rst +++ b/Documentation/filesystems/idmappings.rst @@ -373,6 +373,13 @@ kernel maps the caller's userspace id down into a kernel id according to the caller's idmapping and then maps that kernel id up according to the filesystem's idmapping. +From the implementation point it's worth mentioning how idmappings are represented. +All idmappings are taken from the corresponding user namespace. + + - caller's idmapping (usually taken from ``current_user_ns()``) + - filesystem's idmapping (``sb->s_user_ns``) + - mount's idmapping (``mnt_idmap(vfsmnt)``) + Let's see some examples with caller/filesystem idmapping but without mount idmappings. This will exhibit some problems we can hit. After that we will revisit/reconsider these examples, this time using mount idmappings, to see how -- 2.34.1
