Re: [PATCH 20/22] mm: move hmm_vma_fault to nouveau

Ralph Campbell
2019-07-03T17:49:01Z

On 6/30/19 11:20 PM, Christoph Hellwig wrote:
> hmm_vma_fault is marked as a legacy API to get rid of, but quite suites
> the current nouvea flow. Move it to the only user in preparation for

I didn't quite parse the phrase "quite suites the current nouvea flow."
s/nouvea/nouveau/

> fixing a locking bug involving caller and callee.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

I see where you are going with this and it
looks like straightforward code movement so,

Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>

> ---
> drivers/gpu/drm/nouveau/nouveau_svm.c | 54 ++++++++++++++++++++++++++-
> include/linux/hmm.h | 54 ---------------------------
> 2 files changed, 53 insertions(+), 55 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
> index 9d40114d7949..e831f4184a17 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
> @@ -36,6 +36,13 @@
> #include <linux/sort.h>
> #include <linux/hmm.h>
>
> +/*
> + * When waiting for mmu notifiers we need some kind of time out otherwise we
> + * could potentialy wait for ever, 1000ms ie 1s sounds like a long time to
> + * wait already.
> + */
> +#define NOUVEAU_RANGE_FAULT_TIMEOUT 1000
> +
> struct nouveau_svm {
> struct nouveau_drm *drm;
> struct mutex mutex;
> @@ -475,6 +482,51 @@ nouveau_svm_fault_cache(struct nouveau_svm *svm,
> fault->inst, fault->addr, fault->access);
> }
>
> +static int
> +nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range,
> + bool block)
> +{
> + long ret;
> +
> + /*
> + * With the old API the driver must set each individual entries with
> + * the requested flags (valid, write, ...). So here we set the mask to
> + * keep intact the entries provided by the driver and zero out the
> + * default_flags.
> + */
> + range->default_flags = 0;
> + range->pfn_flags_mask = -1UL;
> +
> + ret = hmm_range_register(range, mirror,
> + range->start, range->end,
> + PAGE_SHIFT);
> + if (ret)
> + return (int)ret;
> +
> + if (!hmm_range_wait_until_valid(range, NOUVEAU_RANGE_FAULT_TIMEOUT)) {
> + /*
> + * The mmap_sem was taken by driver we release it here and
> + * returns -EAGAIN which correspond to mmap_sem have been
> + * drop in the old API.
> + */
> + up_read(&range->vma->vm_mm->mmap_sem);
> + return -EAGAIN;
> + }
> +
> + ret = hmm_range_fault(range, block);
> + if (ret <= 0) {
> + if (ret == -EBUSY || !ret) {
> + /* Same as above, drop mmap_sem to match old API. */
> + up_read(&range->vma->vm_mm->mmap_sem);
> + ret = -EBUSY;
> + } else if (ret == -EAGAIN)
> + ret = -EBUSY;
> + hmm_range_unregister(range);
> + return ret;
> + }
> + return 0;
> +}
> +
> static int
> nouveau_svm_fault(struct nvif_notify *notify)
> {
> @@ -649,7 +701,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
> range.values = nouveau_svm_pfn_values;
> range.pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT;
> again:
> - ret = hmm_vma_fault(&svmm->mirror, &range, true);
> + ret = nouveau_range_fault(&svmm->mirror, &range, true);
> if (ret == 0) {
> mutex_lock(&svmm->mutex);
> if (!hmm_range_unregister(&range)) {
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index 4b185d286c3b..3457cf9182e5 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -478,60 +478,6 @@ long hmm_range_dma_unmap(struct hmm_range *range,
> dma_addr_t *daddrs,
> bool dirty);
>
> -/*
> - * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range
> - *
> - * When waiting for mmu notifiers we need some kind of time out otherwise we
> - * could potentialy wait for ever, 1000ms ie 1s sounds like a long time to
> - * wait already.
> - */
> -#define HMM_RANGE_DEFAULT_TIMEOUT 1000
> -
> -/* This is a temporary helper to avoid merge conflict between trees. */
> -static inline int hmm_vma_fault(struct hmm_mirror *mirror,
> - struct hmm_range *range, bool block)
> -{
> - long ret;
> -
> - /*
> - * With the old API the driver must set each individual entries with
> - * the requested flags (valid, write, ...). So here we set the mask to
> - * keep intact the entries provided by the driver and zero out the
> - * default_flags.
> - */
> - range->default_flags = 0;
> - range->pfn_flags_mask = -1UL;
> -
> - ret = hmm_range_register(range, mirror,
> - range->start, range->end,
> - PAGE_SHIFT);
> - if (ret)
> - return (int)ret;
> -
> - if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
> - /*
> - * The mmap_sem was taken by driver we release it here and
> - * returns -EAGAIN which correspond to mmap_sem have been
> - * drop in the old API.
> - */
> - up_read(&range->vma->vm_mm->mmap_sem);
> - return -EAGAIN;
> - }
> -
> - ret = hmm_range_fault(range, block);
> - if (ret <= 0) {
> - if (ret == -EBUSY || !ret) {
> - /* Same as above, drop mmap_sem to match old API. */
> - up_read(&range->vma->vm_mm->mmap_sem);
> - ret = -EBUSY;
> - } else if (ret == -EAGAIN)
> - ret = -EBUSY;
> - hmm_range_unregister(range);
> - return ret;
> - }
> - return 0;
> -}
> -
> /* Below are for HMM internal use only! Not to be used by device driver! */
> static inline void hmm_mm_init(struct mm_struct *mm)
> {
>