On 9/29/18 10:46 PM, Daniel Black wrote: <snip> > hugetlbfs pages have VM_DONTEXPAND in the VmFlags driver pages based on > author testing with analysis from Florian Weimer[1]. > > The inclusion of VM_DONTEXPAND into the VM_SPECIAL defination > was a consequence of the large useage of VM_DONTEXPAND in device > drivers. > > A consequence of [2] is that VM_DONTEXPAND marked pages are unable to be > marked DODUMP. > > A user could quite legitimately madvise(MADV_DONTDUMP) their hugetlbfs > memory for a while and later request that madvise(MADV_DODUMP) on the > same memory. We correct this omission by allowing madvice(MADV_DODUMP) > on hugetlbfs pages. > > [1] https://stackoverflow.com/questions/52548260/madvisedodump-on-the-same-ptr-size-as-a-successful-madvisedontdump-fails-wit > [2] commit 0103bd16fb90 ("mm: prepare VM_DONTDUMP for using in drivers") > > Fixes: 0103bd16fb90 ("mm: prepare VM_DONTDUMP for using in drivers") > Reported-by: Kenneth Penza <kpenza@xxxxxxxxx> > Signed-off-by: Daniel Black <daniel@xxxxxxxxxxxxx> > Buglink: https://lists.launchpad.net/maria-discuss/msg05245.html > Cc: linux-mm@xxxxxxxxx > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> > --- > mm/madvise.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 972a9eaa898b..71d21df2a3f3 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -96,7 +96,7 @@ static long madvise_behavior(struct vm_area_struct *vma, > new_flags |= VM_DONTDUMP; > break; > case MADV_DODUMP: > - if (new_flags & VM_SPECIAL) { > + if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL) { Thanks Daniel, This is certainly a regression. My only question is whether this condition should be more specific and test the default hugetlb vma flags (VM_DONTEXPAND | VM_HUGETLB). Or, whether simply checking VM_HUGETLB as you have done above is sufficient. Only reason for concern is that I am not 100% certain other VM_SPECIAL flags could not be set in VM_HUGETLB vma. Perhaps Konstantin has an opinion as he did a bunch of the vm_flag reorg. -- Mike Kravetz > error = -EINVAL; > goto out; > } >
