[PATCH 01/18] mm: add a kunmap_local_dirty helper
From: Christoph Hellwig <hch@lst.de>
Date: 2021-06-15 13:26:11
Also in:
ceph-devel, dm-devel, linux-block, linux-mips, linuxppc-dev, lkml
Subsystem:
memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
Add a helper that calls flush_kernel_dcache_page before unmapping the local mapping. flush_kernel_dcache_page is required for all pages potentially mapped into userspace that were written to using kmap*, so having a helper that does the right thing can be very convenient. Signed-off-by: Christoph Hellwig <hch@lst.de> --- include/linux/highmem-internal.h | 7 +++++++ include/linux/highmem.h | 4 ++++ 2 files changed, 11 insertions(+)
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
index 7902c7d8b55f..bd37706db147 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h@@ -224,4 +224,11 @@ do { \ __kunmap_local(__addr); \ } while (0) +#define kunmap_local_dirty(__page, __addr) \ +do { \ + if (!PageSlab(__page)) \ + flush_kernel_dcache_page(__page); \ + kunmap_local(__addr); \ +} while (0) + #endif
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 832b49b50c7b..65f548db4f2d 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h@@ -93,6 +93,10 @@ static inline void kmap_flush_unused(void); * On HIGHMEM enabled systems mapping a highmem page has the side effect of * disabling migration in order to keep the virtual address stable across * preemption. No caller of kmap_local_page() can rely on this side effect. + * + * If data is written to the returned kernel mapping, the callers needs to + * unmap the mapping using kunmap_local_dirty(), else kunmap_local() should + * be used. */ static inline void *kmap_local_page(struct page *page);
--
2.30.2