Cesar Eduardo Barros 597781f3e5 kmap_atomic: make kunmap_atomic() harder to misuse ... kunmap_atomic() is currently at level -4 on Rusty's "Hard To Misuse" list[1] ("Follow common convention and you'll get it wrong"), except in some architectures when CONFIG_DEBUG_HIGHMEM is set[2][3]. kunmap() takes a pointer to a struct page; kunmap_atomic(), however, takes takes a pointer to within the page itself. This seems to once in a while trip people up (the convention they are following is the one from kunmap()). Make it much harder to misuse, by moving it to level 9 on Rusty's list[4] ("The compiler/linker won't let you get it wrong"). This is done by refusing to build if the type of its first argument is a pointer to a struct page. The real kunmap_atomic() is renamed to kunmap_atomic_notypecheck() (which is what you would call in case for some strange reason calling it with a pointer to a struct page is not incorrect in your code). The previous version of this patch was compile tested on x86-64. [1] http://ozlabs.org/~rusty/index.cgi/tech/2008-04-01.html [2] In these cases, it is at level 5, "Do it right or it will always break at runtime." [3] At least mips and powerpc look very similar, and sparc also seems to share a common ancestor with both; there seems to be quite some degree of copy-and-paste coding here. The include/asm/highmem.h file for these three archs mention x86 CPUs at its top. [4] http://ozlabs.org/~rusty/index.cgi/tech/2008-03-30.html [5] As an aside, could someone tell me why mn10300 uses unsigned long as the first parameter of kunmap_atomic() instead of void *? Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net> Cc: Russell King <linux@arm.linux.org.uk> (arch/arm) Cc: Ralf Baechle <ralf@linux-mips.org> (arch/mips) Cc: David Howells <dhowells@redhat.com> (arch/frv, arch/mn10300) Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com> (arch/mn10300) Cc: Kyle McMartin <kyle@mcmartin.ca> (arch/parisc) Cc: Helge Deller <deller@gmx.de> (arch/parisc) Cc: "James E.J. Bottomley" <jejb@parisc-linux.org> (arch/parisc) Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> (arch/powerpc) Cc: Paul Mackerras <paulus@samba.org> (arch/powerpc) Cc: "David S. Miller" <davem@davemloft.net> (arch/sparc) Cc: Thomas Gleixner <tglx@linutronix.de> (arch/x86) Cc: Ingo Molnar <mingo@redhat.com> (arch/x86) Cc: "H. Peter Anvin" <hpa@zytor.com> (arch/x86) Cc: Arnd Bergmann <arnd@arndb.de> (include/asm-generic) Cc: Rusty Russell <rusty@rustcorp.com.au> ("Hard To Misuse" list) Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2010-08-09 20:44:54 -07:00
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asm	kmap_atomic: make kunmap_atomic() harder to misuse	2010-08-09 20:44:54 -07:00