[PATCH] doc: idmappings: fix an error and rephrase a paragraph

[GONG, Ruiqi]

From: "GONG, Ruiqi" <gongruiqi1@xxxxxxxxxx>

If the modified paragraph is referring to the idmapping mentioned in the
previous paragraph (i.e. `u0:k10000:r10000`), then it is `u0` that the
upper idmapset starts with, not `u1000`.

Fix this error and rephrase this paragraph a bit to make this reference
more explicit.

Reported-by: Wang Lei <wanglei249@xxxxxxxxxx>
Signed-off-by: GONG, Ruiqi <gongruiqi1@xxxxxxxxxx>
---
 Documentation/filesystems/idmappings.rst | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/idmappings.rst b/Documentation/filesystems/idmappings.rst
index f3d168c9f0b9..d095c5838f94 100644
--- a/Documentation/filesystems/idmappings.rst
+++ b/Documentation/filesystems/idmappings.rst
@@ -146,9 +146,10 @@ For the rest of this document we will prefix all userspace ids with ``u`` and
 all kernel ids with ``k``. Ranges of idmappings will be prefixed with ``r``. So
 an idmapping will be written as ``u0:k10000:r10000``.
 
-For example, the id ``u1000`` is an id in the upper idmapset or "userspace
-idmapset" starting with ``u1000``. And it is mapped to ``k11000`` which is a
-kernel id in the lower idmapset or "kernel idmapset" starting with ``k10000``.
+For example, within this idmapping, the id ``u1000`` is an id in the upper
+idmapset or "userspace idmapset" starting with ``u0``. And it is mapped to
+``k11000`` which is a kernel id in the lower idmapset or "kernel idmapset"
+starting with ``k10000``.
 
 A kernel id is always created by an idmapping. Such idmappings are associated
 with user namespaces. Since we mainly care about how idmappings work we're not
-- 
2.25.1