On Sun, Jul 18, 2021 at 12:31 PM Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> 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 pte_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 pte_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 use preallocated pte to split huge pmd. s/use/uses a/g s/split huge/split a huge/g > > Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
