From: Peter Xu <peterx@xxxxxxxxxx> Subject: mm/gup: allow to react to fatal signals The existing gup code does not react to the fatal signals in many code paths. For example, in one retry path of gup we're still using down_read() rather than down_read_killable(). Also, when doing page faults we don't pass in FAULT_FLAG_KILLABLE as well, which means that within the faulting process we'll wait in non-killable way as well. These were spotted by Linus during the code review of some other patches. Let's allow the gup code to react to fatal signals to improve the responsiveness of threads when during gup and being killed. Link: http://lkml.kernel.org/r/20200220160256.9887-1-peterx@xxxxxxxxxx Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> Tested-by: Brian Geffon <bgeffon@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Bobby Powers <bobbypowers@xxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Denis Plotnikov <dplotnikov@xxxxxxxxxxxxx> Cc: "Dr . David Alan Gilbert" <dgilbert@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Jerome Glisse <jglisse@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Martin Cracauer <cracauer@xxxxxxxx> Cc: Marty McFadden <mcfadden8@xxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Maya Gokhale <gokhale2@xxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/gup.c | 12 +++++++++--- mm/hugetlb.c | 3 ++- 2 files changed, 11 insertions(+), 4 deletions(-) --- a/mm/gup.c~mm-gup-allow-to-react-to-fatal-signals +++ a/mm/gup.c @@ -864,7 +864,7 @@ static int faultin_page(struct task_stru if (*flags & FOLL_REMOTE) fault_flags |= FAULT_FLAG_REMOTE; if (locked) - fault_flags |= FAULT_FLAG_ALLOW_RETRY; + fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; if (*flags & FOLL_NOWAIT) fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; if (*flags & FOLL_TRIED) { @@ -1207,7 +1207,7 @@ int fixup_user_fault(struct task_struct address = untagged_addr(address); if (unlocked) - fault_flags |= FAULT_FLAG_ALLOW_RETRY; + fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; retry: vma = find_extend_vma(mm, address); @@ -1329,7 +1329,13 @@ retry: break; *locked = 1; - down_read(&mm->mmap_sem); + ret = down_read_killable(&mm->mmap_sem); + if (ret) { + BUG_ON(ret > 0); + if (!pages_done) + pages_done = ret; + break; + } ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED, pages, NULL, locked); --- a/mm/hugetlb.c~mm-gup-allow-to-react-to-fatal-signals +++ a/mm/hugetlb.c @@ -4344,7 +4344,8 @@ long follow_hugetlb_page(struct mm_struc if (flags & FOLL_WRITE) fault_flags |= FAULT_FLAG_WRITE; if (locked) - fault_flags |= FAULT_FLAG_ALLOW_RETRY; + fault_flags |= FAULT_FLAG_ALLOW_RETRY | + FAULT_FLAG_KILLABLE; if (flags & FOLL_NOWAIT) fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; _
