On Tue, Mar 30, 2021 at 12:08 AM John Hubbard <jhubbard@xxxxxxxxxx> wrote:
>
> On 3/29/21 12:38 PM, Yang Shi wrote:
> > Since commit 5a52c9df62b4 ("uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT")
> > and commit ba925fa35057 ("s390/gmap: improve THP splitting") FOLL_SPLIT
> > has not been used anymore. Remove the dead code.
> >
> > Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
> > ---
> > include/linux/mm.h | 1 -
> > mm/gup.c | 28 ++--------------------------
> > 2 files changed, 2 insertions(+), 27 deletions(-)
> >
>
> Looks nice.
>
> As long as I'm running git grep here, there is one more search hit that should also
> be fixed up, as part of a "remove FOLL_SPLIT" patch:
>
> git grep -nw FOLL_SPLIT
> Documentation/vm/transhuge.rst:57:follow_page, the FOLL_SPLIT bit can be specified as a parameter to
>
> Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Thanks. Removed the reference to FOLL_SPLIT in documentation for v2.
>
> thanks,
> --
> John Hubbard
> NVIDIA
>
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 8ba434287387..3568836841f9 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2780,7 +2780,6 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
> > #define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO
> > * and return without waiting upon it */
> > #define FOLL_POPULATE 0x40 /* fault in page */
> > -#define FOLL_SPLIT 0x80 /* don't return transhuge pages, split them */
> > #define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
> > #define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
> > #define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
> > diff --git a/mm/gup.c b/mm/gup.c
> > index e40579624f10..f3d45a8f18ae 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -435,18 +435,6 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
> > }
> > }
> >
> > - if (flags & FOLL_SPLIT && PageTransCompound(page)) {
> > - get_page(page);
> > - pte_unmap_unlock(ptep, ptl);
> > - lock_page(page);
> > - ret = split_huge_page(page);
> > - unlock_page(page);
> > - put_page(page);
> > - if (ret)
> > - return ERR_PTR(ret);
> > - goto retry;
> > - }
> > -
> > /* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
> > if (unlikely(!try_grab_page(page, flags))) {
> > page = ERR_PTR(-ENOMEM);
> > @@ -591,7 +579,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
> > spin_unlock(ptl);
> > return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
> > }
> > - if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) {
> > + if (flags & FOLL_SPLIT_PMD) {
> > int ret;
> > page = pmd_page(*pmd);
> > if (is_huge_zero_page(page)) {
> > @@ -600,19 +588,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
> > split_huge_pmd(vma, pmd, address);
> > if (pmd_trans_unstable(pmd))
> > ret = -EBUSY;
> > - } else if (flags & FOLL_SPLIT) {
> > - if (unlikely(!try_get_page(page))) {
> > - spin_unlock(ptl);
> > - return ERR_PTR(-ENOMEM);
> > - }
> > - spin_unlock(ptl);
> > - lock_page(page);
> > - ret = split_huge_page(page);
> > - unlock_page(page);
> > - put_page(page);
> > - if (pmd_none(*pmd))
> > - return no_page_table(vma, flags);
> > - } else { /* flags & FOLL_SPLIT_PMD */
> > + } else {
> > spin_unlock(ptl);
> > split_huge_pmd(vma, pmd, address);
> > ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
> >
>
