On Mon, May 11, 2026 at 05:03:02AM -0400, Michael S. Tsirkin wrote: > Convert the hugetlb fault and fallocate paths to use __GFP_ZERO. > For pages allocated from the buddy allocator, post_alloc_hook() > handles zeroing. > > Hugetlb surplus pages need special handling because they can be > pre-allocated into the pool during mmap (by hugetlb_acct_memory) > before any page fault. Pool pages are kept around and may need > zeroing long after buddy allocation, so a buddy-level zeroed > hint (consumed at allocation time) cannot track their state. > > Add a bool *zeroed output parameter to alloc_hugetlb_folio() > so callers know whether the page needs zeroing. Buddy-allocated > pages are always zeroed (zeroed by post_alloc_hook). Pool > pages use a new HPG_zeroed flag to track whether the page is > known-zero (freshly buddy-allocated, never mapped to userspace). > The flag is set in alloc_surplus_hugetlb_folio() after buddy > allocation and cleared in free_huge_folio() when a user-mapped > page returns to the pool. > > Callers that do not need zeroing (CoW, migration) pass NULL for > zeroed and 0 for gfp. > > Signed-off-by: Michael S. Tsirkin <[email protected]> > Assisted-by: Claude:claude-opus-4-6 > Assisted-by: cursor-agent:GPT-5.4-xhigh > --- > fs/hugetlbfs/inode.c | 10 ++++++-- > include/linux/hugetlb.h | 8 +++++-- > mm/hugetlb.c | 52 ++++++++++++++++++++++++++++++----------- > 3 files changed, 53 insertions(+), 17 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 8b05bec08e04..24e42cb10ade 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -810,14 +810,20 @@ static long hugetlbfs_fallocate(struct file *file, int > mode, loff_t offset, > * folios in these areas, we need to consume the reserves > * to keep reservation accounting consistent. > */ > - folio = alloc_hugetlb_folio(&pseudo_vma, addr, false); > + { > + bool zeroed; > + > + folio = alloc_hugetlb_folio(&pseudo_vma, addr, false, > + __GFP_ZERO, &zeroed);
This feels like a very odd pattern: 1) ask for __GFP_ZERO 2) Have to check whether it was actually zeroed Seems like the zeroing piece should just be sunk in if you're going to ask for __GFP_ZERO anyway. And in that case, maybe just `bool zero` as an argument, rather than GFP (to avoid future overloading of flags). ~Gregory
