linux-kernel - [PATCH v3 2/2] Documentation/vm: Include kernel-doc to highmem.rst

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Message-Id: <20220415231917.25962-3-fmdefrancesco@gmail.com>
Date:   Sat, 16 Apr 2022 01:19:17 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        SeongJae Park <sj@...nel.org>,
        Jiajian Ye <yejiajian2018@...il.szu.edu.cn>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ira Weiny <ira.weiny@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        outreachy@...ts.linux.dev, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Subject: [PATCH v3 2/2] Documentation/vm: Include kernel-doc to highmem.rst

Include kernel-doc comments to highmem.rst from
include/kernel/highmem.h.

>From now on, the "Using kmap_atomic" section is redundant and obsolete,
therefore remove it.

Cc: Jonathan Corbet <corbet@....net>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ira Weiny <ira.weiny@...el.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
---
 Documentation/vm/highmem.rst | 41 ++++++------------------------------
 1 file changed, 6 insertions(+), 35 deletions(-)

diff --git a/Documentation/vm/highmem.rst b/Documentation/vm/highmem.rst
index 12dcfbee094d..5dcee6233cd5 100644
--- a/Documentation/vm/highmem.rst
+++ b/Documentation/vm/highmem.rst
@@ -117,41 +117,6 @@ The kernel contains several ways of creating temporary mappings:
   synchronization to unmap.
 
 
-Using kmap_atomic
-=================
-
-When and where to use kmap_atomic() is straightforward.  It is used when code
-wants to access the contents of a page that might be allocated from high memory
-(see __GFP_HIGHMEM), for example a page in the pagecache.  The API has two
-functions, and they can be used in a manner similar to the following::
-
-	/* Find the page of interest. */
-	struct page *page = find_get_page(mapping, offset);
-
-	/* Gain access to the contents of that page. */
-	void *vaddr = kmap_atomic(page);
-
-	/* Do something to the contents of that page. */
-	memset(vaddr, 0, PAGE_SIZE);
-
-	/* Unmap that page. */
-	kunmap_atomic(vaddr);
-
-Note that the kunmap_atomic() call takes the result of the kmap_atomic() call
-not the argument.
-
-If you need to map two pages because you want to copy from one page to
-another you need to keep the kmap_atomic calls strictly nested, like::
-
-	vaddr1 = kmap_atomic(page1);
-	vaddr2 = kmap_atomic(page2);
-
-	memcpy(vaddr1, vaddr2, PAGE_SIZE);
-
-	kunmap_atomic(vaddr2);
-	kunmap_atomic(vaddr1);
-
-
 Cost of Temporary Mappings
 ==========================
 
@@ -190,3 +155,9 @@ The general recommendation is that you don't use more than 8GiB on a 32-bit
 machine - although more might work for you and your workload, you're pretty
 much on your own - don't expect kernel developers to really care much if things
 come apart.
+
+
+Functions
+=========
+
+.. kernel-doc:: include/linux/highmem.h
-- 
2.34.1