Dave McCracken [off-list ref] wrote:

--On Thursday, February 27, 2003 13:44:03 -0800 Andrew Morton
[off-list ref] wrote:

quoted

quoted

...
Mapped:       4294923652 kB

Well that's gotta hurt.  This metric is used in making writeback
decisions.  Probably the objrmap patch.

Oops.  You're right.  Here's a patch to fix it.

Thanks.

I'm just looking at page_mapped().  It is now implicitly assuming that the
architecture's representation of a zero-count atomic_t is all-bits-zero.

This is not true on sparc32 if some other CPU is in the middle of an
atomic_foo() against that counter.  Maybe the assumption is false on other
architectures too.

So page_mapped() really should be performing an atomic_read() if that is
appropriate to the particular page.  I guess this involves testing
page->mapping.  Which is stable only when the page is locked or
mapping->page_lock is held.

It appears that all page_mapped() callers are inside lock_page() at present,
so a quick audit and addition of a comment would be appropriate there please.


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