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[PATCH] Add flush_kernel_dcache_page() API

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We have a problem in a lot of emulated storage in that it takes a page from
get_user_pages() and does something like

kmap_atomic(page)
modify page
kunmap_atomic(page)

However, nothing has flushed the kernel cache view of the page before the
kunmap.  We need a lightweight API to do this, so this new API would
specifically be for flushing the kernel cache view of a user page which the
kernel has modified.  The driver would need to add
flush_kernel_dcache_page(page) before the final kunmap.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
James Bottomley 2006-03-26 01:36:59 -08:00 committed by Linus Torvalds
parent 03beb07664
commit 5a3a5a98b6
2 changed files with 18 additions and 0 deletions
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12
Documentation/cachetlb.txt
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@ -371,6 +371,18 @@ maps this page at its virtual address.
architectures). For incoherent architectures, it should flush
the cache of the page at vmaddr in the current user process.
void flush_kernel_dcache_page(struct page *page)
When the kernel needs to modify a user page is has obtained
with kmap, it calls this function after all modifications are
complete (but before kunmapping it) to bring the underlying
page up to date. It is assumed here that the user has no
incoherent cached copies (i.e. the original page was obtained
from a mechanism like get_user_pages()). The default
implementation is a nop and should remain so on all coherent
architectures. On incoherent architectures, this should flush
the kernel cache for page (using page_address(page)).
void flush_icache_range(unsigned long start, unsigned long end)
When the kernel stores into addresses that it will execute
out of (eg when loading modules), this function is called.

6
include/linux/highmem.h
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@ -13,6 +13,12 @@ static inline void flush_anon_page(struct page *page, unsigned long vmaddr)
}
#endif
#ifndef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE
static inline void flush_kernel_dcache_page(struct page *page)
{
}
#endif
#ifdef CONFIG_HIGHMEM
#include <asm/highmem.h>