Using EOR to clear the guaranteed-to-be-set lock bit will test the
negative flag just like the x86 implementation. This should be
more efficient than the generic implementation in filemap.c. It
would be better if m68k had __GCC_ASM_FLAG_OUTPUTS__.
Coldfire doesn't have a byte-sized EOR, so we test bit 7 after the
EOR, which is a second memory access, but it's slightly better than
the current C code.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
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