On Thu, Jun 13, 2024 at 02:42:02PM -0700, Vivek Kasireddy wrote: > Currently, some drivers (e.g, Udmabuf) that want to longterm-pin > the pages/folios associated with a memfd, do so by simply taking a > reference on them. This is not desirable because the pages/folios > may reside in Movable zone or CMA block. > > Therefore, having drivers use memfd_pin_folios() API ensures that > the folios are appropriately pinned via FOLL_PIN for longterm DMA. > > This patchset also introduces a few helpers and converts the Udmabuf > driver to use folios and memfd_pin_folios() API to longterm-pin > the folios for DMA. Two new Udmabuf selftests are also included to > test the driver and the new API. For merging, as soon as the -mm side is good it's imo best to land the entire pile through the -mm tree, including the udmabuf patches. My ack for that too (but I think Dave Airlie has done that already too). Cheers, Sima > > --- > > Patchset overview: > > Patch 1-2: GUP helpers to migrate and unpin one or more folios > Patch 3: Introduce memfd_pin_folios() API > Patch 4-5: Udmabuf driver bug fixes for Qemu + hugetlb=on, blob=true case > Patch 6-8: Convert Udmabuf to use memfd_pin_folios() and add selftests > > This series is tested using the following methods: > - Run the subtests added in Patch 8 > - Run Qemu (master) with the following options and a few additional > patches to Spice: > qemu-system-x86_64 -m 4096m.... > -device virtio-gpu-pci,max_outputs=1,blob=true,xres=1920,yres=1080 > -spice port=3001,gl=on,disable-ticketing=on,preferred-codec=gstreamer:h264 > -object memory-backend-memfd,hugetlb=on,id=mem1,size=4096M > -machine memory-backend=mem1 > - Run source ./run_vmtests.sh -t gup_test -a to check GUP regressions > > Changelog: > > v14 -> v15: > - Add an error check start < 0 in memfd_pin_folios() > - Return an error in udmabuf driver if memfd_pin_folios() returns 0 > These two checks fix the following issue identified by syzbot: > https://syzkaller.appspot.com/bug?extid=40c7dad27267f61839d4 > - Set memfd = NULL before dmabuf export to ensure that memfd is > not closed twice on error. This fixes the following syzbot issue: > https://syzkaller.appspot.com/bug?extid=b2cfdac9ae5278d4b621 > > v13 -> v14: > - Drop the redundant comments before check_and_migrate_movable_pages() > and refer to check_and_migrate_movable_folios() comments (David) > - Use appropriate ksft_* functions for printing and KSFT_* codes for > exit() in udmabuf selftest (Shuah) > - Add Mike Kravetz's suggested-by tag in udmabuf selftest patch (Shuah) > - Collect Ack and Rb tags from David > > v12 -> v13: (suggestions from David) > - Drop the sanity checks in unpin_folio()/unpin_folios() due to > unavailability of per folio anon-exclusive flag > - Export unpin_folio()/unpin_folios() using EXPORT_SYMBOL_GPL > instead of EXPORT_SYMBOL > - Have check_and_migrate_movable_pages() just call > check_and_migrate_movable_folios() instead of calling other helpers > - Slightly improve the comments and commit messages > > v11 -> v12: > - Rebased and tested on mm-unstable > > v10 -> v11: > - Remove the version string from the patch subject (Andrew) > - Move the changelog from the patches into the cover letter > - Rearrange the patchset to have GUP patches at the beginning > > v9 -> v10: > - Introduce and use unpin_folio(), unpin_folios() and > check_and_migrate_movable_folios() helpers > - Use a list to track the folios that need to be unpinned in udmabuf > > v8 -> v9: (suggestions from Matthew) > - Drop the extern while declaring memfd_alloc_folio() > - Fix memfd_alloc_folio() declaration to have it return struct folio * > instead of struct page * when CONFIG_MEMFD_CREATE is not defined > - Use folio_pfn() on the folio instead of page_to_pfn() on head page > in udmabuf > - Don't split the arguments to shmem_read_folio() on multiple lines > in udmabuf > > v7 -> v8: (suggestions from David) > - Have caller pass [start, end], max_folios instead of start, nr_pages > - Replace offsets array with just offset into the first page > - Add comments explaning the need for next_idx > - Pin (and return) the folio (via FOLL_PIN) only once > > v6 -> v7: > - Rename this API to memfd_pin_folios() and make it return folios > and offsets instead of pages (David) > - Don't continue processing the folios in the batch returned by > filemap_get_folios_contig() if they do not have correct next_idx > - Add the R-b tag from Christoph > > v5 -> v6: (suggestions from Christoph) > - Rename this API to memfd_pin_user_pages() to make it clear that it > is intended for memfds > - Move the memfd page allocation helper from gup.c to memfd.c > - Fix indentation errors in memfd_pin_user_pages() > - For contiguous ranges of folios, use a helper such as > filemap_get_folios_contig() to lookup the page cache in batches > - Split the processing of hugetlb or shmem pages into helpers to > simplify the code in udmabuf_create() > > v4 -> v5: (suggestions from David) > - For hugetlb case, ensure that we only obtain head pages from the > mapping by using __filemap_get_folio() instead of find_get_page_flags() > - Handle -EEXIST when two or more potential users try to simultaneously > add a huge page to the mapping by forcing them to retry on failure > > v3 -> v4: > - Remove the local variable "page" and instead use 3 return statements > in alloc_file_page() (David) > - Add the R-b tag from David > > v2 -> v3: (suggestions from David) > - Enclose the huge page allocation code with #ifdef CONFIG_HUGETLB_PAGE > (Build error reported by kernel test robot <lkp@xxxxxxxxx>) > - Don't forget memalloc_pin_restore() on non-migration related errors > - Improve the readability of the cleanup code associated with > non-migration related errors > - Augment the comments by describing FOLL_LONGTERM like behavior > - Include the R-b tag from Jason > > v1 -> v2: > - Drop gup_flags and improve comments and commit message (David) > - Allocate a page if we cannot find in page cache for the hugetlbfs > case as well (David) > - Don't unpin pages if there is a migration related failure (David) > - Drop the unnecessary nr_pages <= 0 check (Jason) > - Have the caller of the API pass in file * instead of fd (Jason) > > Cc: David Hildenbrand <david@xxxxxxxxxx> > Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Peter Xu <peterx@xxxxxxxxxx> > Cc: Jason Gunthorpe <jgg@xxxxxxxxxx> > Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx> > Cc: Dongwon Kim <dongwon.kim@xxxxxxxxx> > Cc: Junxiao Chang <junxiao.chang@xxxxxxxxx> > > Arnd Bergmann (1): > udmabuf: add CONFIG_MMU dependency > > Vivek Kasireddy (8): > mm/gup: Introduce unpin_folio/unpin_folios helpers > mm/gup: Introduce check_and_migrate_movable_folios() > mm/gup: Introduce memfd_pin_folios() for pinning memfd folios > udmabuf: Use vmf_insert_pfn and VM_PFNMAP for handling mmap > udmabuf: Add back support for mapping hugetlb pages > udmabuf: Convert udmabuf driver to use folios > udmabuf: Pin the pages using memfd_pin_folios() API > selftests/udmabuf: Add tests to verify data after page migration > > drivers/dma-buf/Kconfig | 1 + > drivers/dma-buf/udmabuf.c | 232 +++++++++---- > include/linux/memfd.h | 5 + > include/linux/mm.h | 5 + > mm/gup.c | 307 +++++++++++++++--- > mm/memfd.c | 35 ++ > .../selftests/drivers/dma-buf/udmabuf.c | 214 ++++++++++-- > 7 files changed, 662 insertions(+), 137 deletions(-) > > -- > 2.45.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
