On Mon 24-12-18 14:12:51, Mike Rapoport wrote: > On Mon, Dec 24, 2018 at 08:49:16AM +0100, Michal Hocko wrote: > > [Cc-ing mailing list and people involved in the original patch] > > > > On Fri 21-12-18 13:42:24, Paul Oppenheimer wrote: > > > Hello! I've never reported a kernel bug before, and since its on the > > > "next" tree I was told to email the author of the relevant commit. > > > Please redirect me to the correct place if I've made a mistake. > > > > > > When opening firefox or chrome, and using it for a good 7 seconds, it > > > hangs in "uninterruptible sleep" and I recieve a "BUG" in dmesg. This > > > doesn't occur when reverting this commit: > > > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=48cf516f8c. > > > Ive attached the output of decode_stacktrace.sh and the relevant dmesg > > > log to this email. > > > > > > Thanks > > > > > BUG: unable to handle kernel NULL pointer dereference at 00000000000000e8 > > > > Thanks for the bug report! This is offset 232 and that matches > > file->f_mapping as per pahole > > pahole -C file ./vmlinux | grep f_mapping > > struct address_space * f_mapping; /* 232 8 */ > > > > I thought that each file really has to have a mapping. But the following > > should heal the issue and add an extra care. > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index f64733c23067..fc9d70a9fbd1 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -66,6 +66,8 @@ bool transparent_hugepage_enabled(struct vm_area_struct *vma) > > { > > if (vma_is_anonymous(vma)) > > return __transparent_hugepage_enabled(vma); > > + if (!vma->vm_file || !vma->vm_file->f_mapping) > > + return false; > > if (shmem_mapping(vma->vm_file->f_mapping) && shmem_huge_enabled(vma)) > > return __transparent_hugepage_enabled(vma); > > We have vma_is_shmem(), it can be used to replace shmem_mapping() without > adding the check for !vma->vm_file Yes, this looks like a much better choice. Thanks! Andrew, could you fold this in instead. diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f64733c23067..e093cf5e4640 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -66,7 +66,7 @@ bool transparent_hugepage_enabled(struct vm_area_struct *vma) { if (vma_is_anonymous(vma)) return __transparent_hugepage_enabled(vma); - if (shmem_mapping(vma->vm_file->f_mapping) && shmem_huge_enabled(vma)) + if (vma_is_shmem(vma) && shmem_huge_enabled(vma)) return __transparent_hugepage_enabled(vma); return false; -- Michal Hocko SUSE Labs
