[PATCH] docs: proc.rst: update description of VmallocUsed and VmallocChunk

[Herve Vico]

A long time ago the behavior of two /proc/meminfo Vmalloc<...> counters
has been modified twice without updating the doc:

- v4.4 removes the expensive 'vmalloc_info' bookkeeping behind VmallocUsed
  and VmallocChunk, and makes both counters return zero:

  commit a5ad88ce8c7f ("mm: get rid of 'vmalloc_info' from /proc/meminfo")

-  v5.3 reintroduces VmallocUsed, making it now report the physical memory
  allocated by vmalloc() calls rather than the vmalloc VA space:

  commit 97105f0ab7b8 ("mm: vmalloc: show number of vmalloc pages in
                        /proc/meminfo")

Let's update the doc to reflect the current behavior.

Signed-off-by: Herve Vico <herve.vico@xxxxxxxxxxx>
---
 Documentation/filesystems/proc.rst | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index b0c0d1b45b99..4a36ac960417 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -1233,9 +1233,12 @@ Committed_AS
 VmallocTotal
               total size of vmalloc virtual address space
 VmallocUsed
-              amount of vmalloc area which is used
+              Amount of memory allocated by vmalloc() calls.
+              Note that VmallocTotal is a constant that refers to the size of
+              the vmalloc VA space, while VmallocUsed reports the amount of
+              memory allocated by vmalloc() calls.
 VmallocChunk
-              largest contiguous block of vmalloc area which is free
+              Deprecated, hardcoded to zero.
 Percpu
               Memory allocated to the percpu allocator used to back percpu
               allocations. This stat excludes the cost of metadata.

base-commit: d60bc140158342716e13ff0f8aa65642f43ba053
-- 
2.51.2