linux-kernel - [v2][PATCH] proc: fix documentation and description of pagemap

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Date:   Tue, 1 Mar 2022 12:45:38 +0800
From:   Yun Zhou <yun.zhou@...driver.com>
To:     <akpm@...ux-foundation.org>, <corbet@....net>, <peterx@...hat.com>,
        <yun.zhou@...driver.com>
CC:     <tiberiu.georgescu@...anix.com>, <florian.schmidt@...anix.com>,
        <ivan.teterevkov@...anix.com>, <sj@...nel.org>,
        <shy828301@...il.com>, <david@...hat.com>,
        <axelrasmussen@...gle.com>, <linmiaohe@...wei.com>,
        <aarcange@...hat.com>, <ccross@...gle.com>, <apopple@...dia.com>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>
Subject: [v2][PATCH] proc: fix documentation and description of pagemap

Since bit 57 was exported for uffd-wp write-protected(commit fb8e37f35a2f),
fixing it can reduce some unnecessary confusion.

Signed-off-by: Yun Zhou <yun.zhou@...driver.com>
---
 Documentation/admin-guide/mm/pagemap.rst | 2 +-
 fs/proc/task_mmu.c                       | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
index bfc28704856c..6e2e416af783 100644
--- a/Documentation/admin-guide/mm/pagemap.rst
+++ b/Documentation/admin-guide/mm/pagemap.rst
@@ -23,7 +23,7 @@ There are four components to pagemap:
     * Bit  56    page exclusively mapped (since 4.2)
     * Bit  57    pte is uffd-wp write-protected (since 5.13) (see
       :ref:`Documentation/admin-guide/mm/userfaultfd.rst <userfaultfd>`)
-    * Bits 57-60 zero
+    * Bits 58-60 zero
     * Bit  61    page is file-page or shared-anon (since 3.5)
     * Bit  62    page swapped
     * Bit  63    page present
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 78125ef20255..2f110089d50e 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1596,7 +1596,8 @@ static const struct mm_walk_ops pagemap_ops = {
  * Bits 5-54  swap offset if swapped
  * Bit  55    pte is soft-dirty (see Documentation/admin-guide/mm/soft-dirty.rst)
  * Bit  56    page exclusively mapped
- * Bits 57-60 zero
+ * Bit  57    pte is uffd-wp write-protected
+ * Bits 58-60 zero
  * Bit  61    page is file-page or shared-anon
  * Bit  62    page swapped
  * Bit  63    page present
-- 
2.27.0