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 <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ira Weiny <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Fabio M. De Francesco <[email protected]>
---
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
On Sat, Apr 16, 2022 at 01:19:17AM +0200, Fabio M. De Francesco wrote:
> 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 <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ira Weiny <[email protected]>
> Cc: Matthew Wilcox <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Signed-off-by: Fabio M. De Francesco <[email protected]>
Reviewed-by: Ira Weiny <[email protected]>
> ---
> 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
>