Messages in this thread Patch in this message | | | From | ira.weiny@intel ... | Subject | [PATCH] highmem: Document kunmap_local() | Date | Sun, 23 Jan 2022 17:30:44 -0800 |
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From: Ira Weiny <ira.weiny@intel.com>
Some users of kmap() add an offset to the kmap() address to be used during the mapping.
When converting to kmap_local_page() the base address does not need to be stored because any address within the page can be used in kunmap_local(). However, this was not clear from the documentation and caused some questions.[1]
Document that any address in the page can be used in kunmap_local() to clarify this for future users.
[1] https://lore.kernel.org/lkml/20211213154543.GM3538886@iweiny-DESK2.sc.intel.com/
Signed-off-by: Ira Weiny <ira.weiny@intel.com> --- include/linux/highmem-internal.h | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h index 0a0b2b09b1b8..fb2d3e033c01 100644 --- a/include/linux/highmem-internal.h +++ b/include/linux/highmem-internal.h @@ -246,6 +246,17 @@ do { \ __kunmap_atomic(__addr); \ } while (0) +/** + * kunmap_local - Unmap a page mapped via kmap_local_page(). + * @__addr: An address within the page mapped + * + * __addr is often an address returned from kmap_local_page(). However, + * this address can be any address within the mapped page. It does not need to + * be the exact address returned from kmap_local_page() + * + * Unmapping should be done in the reverse order of the mapping. See + * kmap_local_page() for details. + */ #define kunmap_local(__addr) \ do { \ BUILD_BUG_ON(__same_type((__addr), struct page *)); \ -- 2.31.1
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