Commit 5a3a5a98 authored by James Bottomley's avatar James Bottomley Committed by Linus Torvalds
Browse files

[PATCH] Add flush_kernel_dcache_page() API 



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: default avatarJames Bottomley <James.Bottomley@SteelEye.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 03beb076

Documentation/cachetlb.txt

+12 −0
Original line number Diff line number Diff line
@@ -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.

include/linux/highmem.h

+6 −0
Original line number Diff line number Diff line
@@ -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>

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