Sorry -- noticed only too late that there are still many false-negatives for THPeligible, since by this point in the function we've already applied sysfs and prctl restrictions, which file-fault ignores. VM_HUGEPAGE also needs to be checked for the file-fault case. On Fri, Aug 18, 2023 at 2:15 PM Zach O'Keefe <zokeefe@xxxxxxxxxx> wrote: > > File-backed memory can be backed by THPs either through collapse, when > CONFIG_READ_ONLY_THP_FOR_FS is enabled, or through fault, when the > filesystem supports large folio mappings. > > Currently, smaps only knows about the former, so teach it about the > latter. > > Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > --- > mm/huge_memory.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index cd379b2c077b..d8d6e83820f3 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -136,7 +136,16 @@ bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags, > */ > !!vma->vm_ops->huge_fault : > /* Only regular file is valid in collapse path */ > - file_thp_enabled(vma); > + file_thp_enabled(vma) || > + /* > + * THPeligible bit of smaps should surface the > + * possibility of THP through fault if the filesystem > + * supports it. We don't check this in fault path, > + * because we want to fallback to the actual ->fault() > + * handler to make the decision. > + */ > + (smaps && vma->vm_file && > + mapping_large_folio_support(vma->vm_file->f_mapping)); > > if (vma_is_temporary_stack(vma)) > return false; > -- > 2.42.0.rc1.204.g551eb34607-goog >
