K 10
svn:author
V 3
alc
K 8
svn:date
V 27
2012-08-17T05:02:29.016651Z
K 7
svn:log
V 853
Fix two problems with pmap_clear_modify().

First, pmap_clear_modify() is write protecting all mappings to the specified
page, not just clearing the modified bit.  Specifically, it sets PTE_RO on
the PTE, which is wrong.  Moreover, it is calling vm_page_dirty(), which is
not the expected behavior for pmap_clear_modify().  Generally speaking, the
machine-independent VM layer masks these mistakes.  For example, setting
PTE_RO will result in additional soft faults, but not a catastrophe.

Second, pmap_clear_modify() may not clear the modified bits because it only
iterates over the PV list when the page has the PV_TABLE_MOD flag set and
elsewhere the pmap clears the PV_TABLE_MOD flag anytime a modified mapping
is write protected or destroyed.  However, the page may still have other
mappings with the modified bit set.

Eliminate a stale comment.

END