Chris Wright wrote:
* Stefan Richter (stefanr@xxxxxxxxxxxxxxxxx) wrote:
-#ifdef CONFIG_DEBUG_PAGE_TYPE
+#if 0 /* debug page type */
<snip>
This misnamed CONFIG_DEBUG_PAGE_TYPE (it's not a Kconfig variable) has
about 120 lines debug code dangling on it. So, replacing it by #if 0
will hopefully motivate a kind janitor to send a removal patch for that
debug code eventually. I don't do so just now because that code went in
between 2.6.20 and 2.6.21-rc1, i.e. not so long ago.
This is Zach's code, his final call. I know it was pretty useful early
on, and used to be an actual Kconfig option for VMI. However, it's
completely disconnected; the setup call to vmi_apply_boot_page_allocations
isn't merged and the page->type field isn't either (no surprise on that),
and some of the VMI_PAGE_ constants have changed names. Clearly, it is
ripe for bitrot (already has !CONFIG_NEED_MULTIPLE_NODES dependency,
dunno if VMI has the same limitation). It definitely should not have
a misleading Kconfig name. I'd nuke it all rather than #if 0.
thanks,
-chris
I'd rather keep it, even with bitrot - it was non-trivial to get
correct, and found many surprises in the code; most notably, it can detect
1) PTE writes to pages not declared as page tables
2) Failure to allocate or de-allocate page tables using the paravirt-ops API
3) PTE writes using the wrong level operations
These are most useful properties; in fact, I would like to extend the
code for 64-bit paravirt-ops and 4-level paging, so rather not kill it
until then.
I never merged the whole bit upstream because it added a field to struct
page.
Zach
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