On Tue, Aug 31, 2021 at 09:21:11PM +0800, Qi Zheng wrote: > The smp_wmb() which is in the __pte_alloc() is used to > ensure all ptes setup is visible before the pte is made > visible to other CPUs by being put into page tables. We > only need this when the pte is actually populated, so > move it to pmd_install(). __pte_alloc_kernel(), > __p4d_alloc(), __pud_alloc() and __pmd_alloc() are similar > to this case. > > We can also defer smp_wmb() to the place where the pmd entry > is really populated by preallocated pte. There are two kinds > of user of preallocated pte, one is filemap & finish_fault(), > another is THP. The former does not need another smp_wmb() > because the smp_wmb() has been done by pmd_install(). > Fortunately, the latter also does not need another smp_wmb() > because there is already a smp_wmb() before populating the > new pte when the THP uses a preallocated pte to split a huge > pmd. > > Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> > Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> > Acked-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> -- Kirill A. Shutemov
