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Subject[PATCH] mm/highmem: Align-down to page the address for kunmap_flush_on_unmap()
Date
If ARCH_HAS_FLUSH_ON_KUNMAP is defined (PA-RISC case), __kunmap_local()
calls kunmap_flush_on_unmap(). The latter currently flushes the wrong
address (as confirmed by Matthew Wilcox and Helge Deller). Al Viro
proposed to call kunmap_flush_on_unmap() on an aligned-down to page
address in order to fix this issue. Consensus has been reached on this
solution.

Therefore, if ARCH_HAS_FLUSH_ON_KUNMAP is defined, call
kunmap_flush_on_unmap() on an aligned-down to page address computed with
the PTR_ALIGN_DOWN() macro.

Cc: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Confirmed-by: Helge Deller <deller@gmx.de>
Confirmed-by: Matthew Wilcox <willy@infradead.org>
Fixes: f3ba3c710ac5 ("mm/highmem: Provide kmap_local*")
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

I have (at least) two problems with this patch...

1) checkpatch.pl complains about the use of the non-standard
"Confirmed-by" tags. I don't know how else I can give credit to Helge
and Matthew. However, this is not the first time that I see non-standard
tags in patches applied upstream (I too had a non-standard
"Analysed-by" tag in patch which fixes a SAC bug). Any objections?

2) I'm not sure whether or not the "Fixes" tag is appropriate in this
patch. Can someone either confirm or deny it?

include/linux/highmem-internal.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
index 034b1106d022..e247c9ac4583 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h
@@ -200,7 +200,7 @@ static inline void *kmap_local_pfn(unsigned long pfn)
static inline void __kunmap_local(const void *addr)
{
#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
- kunmap_flush_on_unmap(addr);
+ kunmap_flush_on_unmap(PTR_ALIGN_DOWN(addr, PAGE_SIZE));
#endif
}

--
2.39.0
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