On Wed, Aug 14, 2019 at 09:59:19AM +0200, Christoph Hellwig wrote: > There isn't any good reason to pass callbacks to migrate_vma. Instead > we can just export the three steps done by this function to drivers and > let them sequence the operation without callbacks. This removes a lot > of boilerplate code as-is, and will allow the drivers to drastically > improve code flow and error handling further on. > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx> > --- > Documentation/vm/hmm.rst | 55 +----- > drivers/gpu/drm/nouveau/nouveau_dmem.c | 122 +++++++------ > include/linux/migrate.h | 118 ++---------- > mm/migrate.c | 244 +++++++++++-------------- > 4 files changed, 195 insertions(+), 344 deletions(-) The mechanical transformation looks OK, I squashed the below nits in, let me know if I got it wrong Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx> diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 4f81c77059e305..0a5960beccf76d 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -339,9 +339,8 @@ Migration to and from device memory =================================== Because the CPU cannot access device memory, migration must use the device DMA -engine to perform copy from and to device memory. For this we need a new to -use migrate_vma_setup(), migrate_vma_pages(), and migrate_vma_finalize() -helpers. +engine to perform copy from and to device memory. For this we need to use +migrate_vma_setup(), migrate_vma_pages(), and migrate_vma_finalize() helpers. Memory cgroup (memcg) and rss accounting diff --git a/mm/migrate.c b/mm/migrate.c index 993386cb53358d..0e78ebd720c0e4 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2622,10 +2622,9 @@ static void migrate_vma_unmap(struct migrate_vma *migrate) * successfully migrated, and which were not. Successfully migrated pages will * have the MIGRATE_PFN_MIGRATE flag set for their src array entry. * - * It is safe to update device page table from within the finalize_and_map() - * callback because both destination and source page are still locked, and the - * mmap_sem is held in read mode (hence no one can unmap the range being - * migrated). + * It is safe to update device page table after migrate_vma_pages() because + * both destination and source page are still locked, and the mmap_sem is held + * in read mode (hence no one can unmap the range being migrated). * * Once the caller is done cleaning up things and updating its page table (if it * chose to do so, this is not an obligation) it finally calls @@ -2657,10 +2656,11 @@ int migrate_vma_setup(struct migrate_vma *args) args->npages = 0; migrate_vma_collect(args); - if (args->cpages) - migrate_vma_prepare(args); - if (args->cpages) - migrate_vma_unmap(args); + if (!args->cpages) + return 0; + + migrate_vma_prepare(args); + migrate_vma_unmap(args); /* * At this point pages are locked and unmapped, and thus they have
