On Wed, 2015-05-27 at 10:56 -0700, Mike Kravetz wrote: > alloc_huge_page and hugetlb_reserve_pages use region_chg to > calculate the number of pages which will be added to the reserve > map. Subpool and global reserve counts are adjusted based on > the output of region_chg. Before the pages are actually added > to the reserve map, these routines could race and add fewer > pages than expected. If this happens, the subpool and global > reserve counts are not correct. > > Compare the number of pages actually added (region_add) to those > expected to added (region_chg). If fewer pages are actually added, > this indicates a race and adjust counters accordingly. > > Signed-off-by: Mike Kravetz <[email protected]>
Reviewed-by: Davidlohr Bueso <[email protected]> With one nit below. > --- > mm/hugetlb.c | 34 ++++++++++++++++++++++++++++++---- > 1 file changed, 30 insertions(+), 4 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index b3d3d59..038c84e 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1544,7 +1544,7 @@ static struct page *alloc_huge_page(struct > vm_area_struct *vma, > struct hugepage_subpool *spool = subpool_vma(vma); > struct hstate *h = hstate_vma(vma); > struct page *page; > - long chg; > + long chg, commit; > int ret, idx; > struct hugetlb_cgroup *h_cg; > > @@ -1585,7 +1585,20 @@ static struct page *alloc_huge_page(struct > vm_area_struct *vma, > > set_page_private(page, (unsigned long)spool); > > - vma_commit_reservation(h, vma, addr); > + commit = vma_commit_reservation(h, vma, addr); > + if (unlikely(chg > commit)) { > + /* > + * The page was added to the reservation map between > + * vma_needs_reservation and vma_commit_reservation. > + * This indicates a race with hugetlb_reserve_pages. > + * Adjust for the subpool count incremented above AND > + * in hugetlb_reserve_pages for the same page. Also, > + * the reservation count added in hugetlb_reserve_pages > + * no longer applies. > + */ > + hugepage_subpool_put_pages(spool, 1); > + hugetlb_acct_memory(h, -1); Should these fixups be encapsulated in a helper? The comment is the same for both alloc_huge_page and hugetlb_reserve_pages. Thanks, Davidlohr > + } > return page; > > out_uncharge_cgroup: > @@ -3699,8 +3712,21 @@ int hugetlb_reserve_pages(struct inode *inode, > * consumed reservations are stored in the map. Hence, nothing > * else has to be done for private mappings here > */ > - if (!vma || vma->vm_flags & VM_MAYSHARE) > - region_add(resv_map, from, to); > + if (!vma || vma->vm_flags & VM_MAYSHARE) { > + long add = region_add(resv_map, from, to); > + > + if (unlikely(chg > add)) { > + /* > + * pages in this range were added to the reserve > + * map between region_chg and region_add. This > + * indicates a race with alloc_huge_page. Adjust > + * the subpool and reserve counts modified above > + * based on the difference. > + */ > + hugepage_subpool_put_pages(spool, chg - add); > + hugetlb_acct_memory(h, -(chg - ret)); > + } > + } > return 0; > out_err: > if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
