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| author | Ira Weiny <ira.weiny@intel.com> | 2022-03-23 00:47:58 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-23 01:57:11 +0300 |
| commit | d7ca25c53e25a9a628aaa19b5a031f115d8c353d (patch) | |
| tree | 1a677c54404423c7427d27fb06c3ddb354872f9e | |
| parent | be4893d92b6b426357978ed955190c0ead23a4b1 (diff) | |
| download | linux-d7ca25c53e25a9a628aaa19b5a031f115d8c353d.tar.xz | |
highmem: document kunmap_local()
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
cause 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/
[ira.weiny@intel.com: updates per Christoph]
Link: https://lkml.kernel.org/r/20220124182138.816693-1-ira.weiny@intel.com
Link: https://lkml.kernel.org/r/20220124013045.806718-1-ira.weiny@intel.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/highmem-internal.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h index 0a0b2b09b1b8..a77be5630209 100644 --- a/include/linux/highmem-internal.h +++ b/include/linux/highmem-internal.h @@ -246,6 +246,16 @@ do { \ __kunmap_atomic(__addr); \ } while (0) +/** + * kunmap_local - Unmap a page mapped via kmap_local_page(). + * @__addr: An address within the page mapped + * + * @__addr can be any address within the mapped page. Commonly it is the + * address return from kmap_local_page(), but it can also include offsets. + * + * 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 *)); \ |