linux-kernel - [PATCH v2 2/7] highmem: Specify that kmap_local

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Date:   Thu, 28 Jul 2022 17:48:39 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Will Deacon <will@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Subject: [PATCH v2 2/7] highmem: Specify that kmap_local_page() is callable from interrupts

In a recent thread about converting kmap() to kmap_local_page(), the
safety of calling kmap_local_page() was questioned.[1]

"any context" should probably be enough detail for users who want to
know whether or not kmap_local_page() can be called from interrupts.
However, Linux still has kmap_atomic() which might make users think they
must use the latter in interrupts.

Add "including interrupts" for better clarity.

[1] https://lore.kernel.org/lkml/3187836.aeNJFYEL58@opensuse/

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Matthew Wilcox (Oracle) <willy@...radead.org>
Cc: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Thomas Gleixner <tglx@...utronix.de>
Suggested-by: Ira Weiny <ira.weiny@...el.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
---
 include/linux/highmem.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index accd286a6af5..0ba031ad29c2 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -64,7 +64,7 @@ static inline void kmap_flush_unused(void);
  *
  * Returns: The virtual address of the mapping
  *
- * Can be invoked from any context.
+ * Can be invoked from any context, including interrupts.
  *
  * Requires careful handling when nesting multiple mappings because the map
  * management is stack based. The unmap has to be in the reverse order of
-- 
2.37.1