linux-kernel - Re: [PATCH v2] mm/highmem: Add notes about conversions from kmap{,

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Message-ID: <Y5FmjdBNEO8aP/Ls@debian.me>
Date:   Thu, 8 Dec 2022 11:22:37 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Ira Weiny <ira.weiny@...el.com>,
        Mike Rapoport <rppt@...nel.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Mike Rapoport <rppt@...ux.ibm.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2] mm/highmem: Add notes about conversions from
 kmap{,_atomic}()

On Wed, Dec 07, 2022 at 11:53:08PM +0100, Fabio M. De Francesco wrote:
> diff --git a/Documentation/mm/highmem.rst b/Documentation/mm/highmem.rst
> index 0f731d9196b0..59d1078f53df 100644
> --- a/Documentation/mm/highmem.rst
> +++ b/Documentation/mm/highmem.rst
> @@ -57,7 +57,8 @@ list shows them in order of preference of use.
>    It can be invoked from any context (including interrupts) but the mappings
>    can only be used in the context which acquired them.
>  
> -  This function should be preferred, where feasible, over all the others.
> +  This function should always be used. kmap_atomic() and kmap() have been
> +  deprecated.

"... always be used, whereas ..."

> +  NOTE: Conversions to kmap_local_page() must take care to follow the mapping
> +  restrictions imposed on kmap_local_page(). Furthermore, the code between
> +  calls to kmap_atomic() and kunmap_atomic() may implicitly depend on the side
> +  effects of atomic mappings, i.e. disabling page faults or preemption, or both.
> +  In that case, explicit calls to pagefault_disable() or preempt_disable() or
> +  both must be made in conjunction with the use of kmap_local_page().
> +
> <snipped>...
> +  NOTE: Conversions to kmap_local_page() must take care to follow the mapping
> +  restrictions imposed on kmap_local_page(). In particular, it is necessary to
> +  make sure that the kernel virtual memory pointer is only valid in the thread
> +  that obtained it.
> +

What about using note block to signify conversion notes above?

---- >8 ----

diff --git a/Documentation/mm/highmem.rst b/Documentation/mm/highmem.rst
index 59d1078f53df57..ef53eb580d4cda 100644
--- a/Documentation/mm/highmem.rst
+++ b/Documentation/mm/highmem.rst
@@ -103,12 +103,14 @@ list shows them in order of preference of use.
 
 * kmap_atomic(). This function has been deprecated; use kmap_local_page().
 
-  NOTE: Conversions to kmap_local_page() must take care to follow the mapping
-  restrictions imposed on kmap_local_page(). Furthermore, the code between
-  calls to kmap_atomic() and kunmap_atomic() may implicitly depend on the side
-  effects of atomic mappings, i.e. disabling page faults or preemption, or both.
-  In that case, explicit calls to pagefault_disable() or preempt_disable() or
-  both must be made in conjunction with the use of kmap_local_page().
+  .. note::
+     Conversions to kmap_local_page() must take care to follow the mapping
+     restrictions imposed on kmap_local_page(). Furthermore, the code between
+     calls to kmap_atomic() and kunmap_atomic() may implicitly depend on the
+     side effects of atomic mappings, i.e. disabling page faults or preemption,
+     or both. In that case, explicit calls to pagefault_disable() or
+     preempt_disable() or both must be made in conjunction with the use of
+     kmap_local_page().
 
   [Legacy documentation]
 
@@ -129,10 +131,11 @@ list shows them in order of preference of use.
 
 * kmap(). This function has been deprecated; use kmap_local_page().
 
-  NOTE: Conversions to kmap_local_page() must take care to follow the mapping
-  restrictions imposed on kmap_local_page(). In particular, it is necessary to
-  make sure that the kernel virtual memory pointer is only valid in the thread
-  that obtained it.
+  .. note::
+     Conversions to kmap_local_page() must take care to follow the mapping
+     restrictions imposed on kmap_local_page(). In particular, it is necessary
+     to make sure that the kernel virtual memory pointer is only valid in the
+     thread that obtained it.
 
   [Legacy documentation]
 
Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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