| Message ID | 20240417092313.753919-3-david@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fs/proc/task_mmu: convert hugetlb functions to work on folis | expand |
On Wed, Apr 17, 2024 at 11:23:13AM +0200, David Hildenbrand wrote: > Let's get rid of another page_mapcount() check and simply use > folio_likely_mapped_shared(), which is precise for hugetlb folios. > > While at it, use huge_ptep_get() + pte_page() instead of ptep_get() + > vm_normal_page(), just like we do in pagemap_hugetlb_range(). That is fine because vm_normal_page() tries to be clever about mappings which hugetlb does not support, right? > > No functional change intended. > > Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Oscar Salvador <osalvador@suse.de>
On 17.04.24 14:09, Oscar Salvador wrote: > On Wed, Apr 17, 2024 at 11:23:13AM +0200, David Hildenbrand wrote: >> Let's get rid of another page_mapcount() check and simply use >> folio_likely_mapped_shared(), which is precise for hugetlb folios. >> >> While at it, use huge_ptep_get() + pte_page() instead of ptep_get() + >> vm_normal_page(), just like we do in pagemap_hugetlb_range(). > > That is fine because vm_normal_page() tries to be clever about mappings which > hugetlb does not support, right? Right, using vm_normal_page() is even completely bogus. Usually (but not always) we have PMDs/PUDs and not PTEs for mapping hugetlb pages -- where vm_normal_folio_pmd() would be the right thing to do. That's also the reason why hugetlb.c has not a single user of vm_normal_page() and friends ... it doesn't apply to hugetlb, but likely also isn't currently harmful to use it.
On Wed, Apr 17, 2024 at 02:18:10PM +0200, David Hildenbrand wrote: > On 17.04.24 14:09, Oscar Salvador wrote: > > On Wed, Apr 17, 2024 at 11:23:13AM +0200, David Hildenbrand wrote: > > > Let's get rid of another page_mapcount() check and simply use > > > folio_likely_mapped_shared(), which is precise for hugetlb folios. > > > > > > While at it, use huge_ptep_get() + pte_page() instead of ptep_get() + > > > vm_normal_page(), just like we do in pagemap_hugetlb_range(). > > > > That is fine because vm_normal_page() tries to be clever about mappings which > > hugetlb does not support, right? > > Right, using vm_normal_page() is even completely bogus. Usually (but not > always) we have PMDs/PUDs and not PTEs for mapping hugetlb pages -- where > vm_normal_folio_pmd() would be the right thing to do. > > That's also the reason why hugetlb.c has not a single user of > vm_normal_page() and friends ... it doesn't apply to hugetlb, but likely > also isn't currently harmful to use it. I guess not because we skip the special handling, but I agree that replacing it is the right thing to do. Thanks for explaining!
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index cd6e45e0cde8e..f4259b7edfded 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -730,19 +730,20 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask, { struct mem_size_stats *mss = walk->private; struct vm_area_struct *vma = walk->vma; - struct page *page = NULL; - pte_t ptent = ptep_get(pte); + pte_t ptent = huge_ptep_get(pte); + struct folio *folio = NULL; if (pte_present(ptent)) { - page = vm_normal_page(vma, addr, ptent); + folio = page_folio(pte_page(ptent)); } else if (is_swap_pte(ptent)) { swp_entry_t swpent = pte_to_swp_entry(ptent); if (is_pfn_swap_entry(swpent)) - page = pfn_swap_entry_to_page(swpent); + folio = pfn_swap_entry_folio(swpent); } - if (page) { - if (page_mapcount(page) >= 2 || hugetlb_pmd_shared(pte)) + if (folio) { + if (folio_likely_mapped_shared(folio) || + hugetlb_pmd_shared(pte)) mss->shared_hugetlb += huge_page_size(hstate_vma(vma)); else mss->private_hugetlb += huge_page_size(hstate_vma(vma));
Let's get rid of another page_mapcount() check and simply use folio_likely_mapped_shared(), which is precise for hugetlb folios. While at it, use huge_ptep_get() + pte_page() instead of ptep_get() + vm_normal_page(), just like we do in pagemap_hugetlb_range(). No functional change intended. Signed-off-by: David Hildenbrand <david@redhat.com> --- fs/proc/task_mmu.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)