On Mon, Sep 07, 2020 at 08:00:57PM +0200, Gerald Schaefer wrote: > From: Alexander Gordeev <agordeev@xxxxxxxxxxxxx> > > Unlike all other page-table abstractions pXd_addr_end() do not take > into account a particular table entry in which context the functions > are called. On architectures with dynamic page-tables folding that > might lead to lack of necessary information that is difficult to > obtain other than from the table entry itself. That already led to > a subtle memory corruption issue on s390. > > By letting pXd_addr_end() functions know about the page-table entry > we allow archs not only make extra checks, but also optimizations. > > As result of this change the pXd_addr_end_folded() functions used > in gup_fast traversal code become unnecessary and get replaced with > universal pXd_addr_end() variants. > > The arch-specific updates not only add dereferencing of page-table > entry pointers, but also small changes to the code flow to make those > dereferences possible, at least for x86 and powerpc. Also for arm64, > but in way that should not have any impact. > > So, even though the dereferenced page-table entries are not used on > archs other than s390, and are optimized out by the compiler, there > is a small change in kernel size and this is what bloat-o-meter reports: This looks pretty clean and straightfoward, only __munlock_pagevec_fill() had any real increased complexity. Thanks, Jason
