> Subject: Re: [PATCH V1 0/5] memfd-pin huge page fixes > > On 9/3/2024 9:12 PM, Kasireddy, Vivek wrote: > > Hi Steve, > > > >> Subject: [PATCH V1 0/5] memfd-pin huge page fixes > >> > >> Fix multiple bugs that occur when using memfd_pin_folios with hugetlb > >> pages > >> and THP. The hugetlb bugs only bite when the page is not yet faulted in > >> when memfd_pin_folios is called. The THP bug bites when the starting > offset > >> passed to memfd_pin_folios is not huge page aligned. See the commit > >> messages > >> for details. > > Thank you for fixing these bugs. I have Acked all patches except for patch > #1, > > as my understanding of xarrays is limited at this point. > > > > Also, could you please briefly describe how you have exercised > memfd_alloc_folio() > > code path or what tests you have run to uncover these bugs? I'd like to > > figure out ways to augment the list of udmabuf tests to validate scenarios > > where hugetlb pages are not faulted in and memfd_pin_folios() is called. > > I am extending iommufd to support memfd pinning, so I added a new ioctl > which > takes an fd, offset, and length to pin. I am just getting started, so currently > it does nothing more than call memfd_pin_folios immediately followed by > unpin_folios. > Then exit the process. That is sufficient to trigger all the bugs except the alloc > race panic. I tested with these files: > /dev/hugepages/file > /dev/shm/file with: mount -o remount,huge=always /dev/shm > memfd_create(MFD_HUGETLB) > memfd_create(0) with: echo always > > /sys/kernel/mm/transparent_hugepage/shmem_enabled Thank you for explaining your test-case. Thanks, Vivek > > - Steve > > >> Steve Sistare (5): > >> mm/filemap: fix filemap_get_folios_contig THP panic > >> mm/hugetlb: fix memfd_pin_folios free_huge_pages leak > >> mm/hugetlb: fix memfd_pin_folios resv_huge_pages leak > >> mm/gup: fix memfd_pin_folios hugetlb page allocation > >> mm/gup: fix memfd_pin_folios alloc race panic > >> > >> include/linux/hugetlb.h | 10 ++++++++++ > >> mm/filemap.c | 4 ++++ > >> mm/gup.c | 5 ++++- > >> mm/hugetlb.c | 17 +++++++++++++++++ > >> mm/memfd.c | 15 +++++++++------ > >> 5 files changed, 44 insertions(+), 7 deletions(-) > >> > >> -- > >> 1.8.3.1 > >
