The patch titled
Subject: Documentation/vm: remove "Using kmap-atomic" from highmem.rst.
has been added to the -mm tree. Its filename is
documentation-vm-remove-using-kmap-atomic-from-highmemrst.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/documentation-vm-remove-using-kmap-atomic-from-highmemrst.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/documentation-vm-remove-using-kmap-atomic-from-highmemrst.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: "Fabio M. De Francesco" <fmdefrancesco@xxxxxxxxx>
Subject: Documentation/vm: remove "Using kmap-atomic" from highmem.rst.
The use of kmap_atomic() is deprecated in favor of kmap_local_page(). For
this reason the "Using kmap_atomic" section in highmem.rst is obsolete and
unnecessary.
Therefore, just remove it.
Link: https://lkml.kernel.org/r/20220421180200.16901-4-fmdefrancesco@xxxxxxxxx
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/highmem.rst | 35 ---------------------------------
1 file changed, 35 deletions(-)
--- a/Documentation/vm/highmem.rst~documentation-vm-remove-using-kmap-atomic-from-highmemrst
+++ a/Documentation/vm/highmem.rst
@@ -72,41 +72,6 @@ The kernel contains several ways of crea
It may be assumed that k[un]map_atomic() won't fail.
-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
==========================
_
Patches currently in -mm which might be from fmdefrancesco@xxxxxxxxx are
mm-highmem-fix-kernel-doc-warnings-in-highmemh.patch
documentation-vm-include-kdocs-from-highmemh-into-highmemrst.patch
documentation-vm-remove-using-kmap-atomic-from-highmemrst.patch
documentation-vm-rework-temporary-virtual-mappings.patch
