From 2bcbeaefde2f0384d6ad351c151b1a9fe7791a0a Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 24 Jul 2019 08:52:52 +0200 Subject: mm/hmm: always return EBUSY for invalid ranges in hmm_range_{fault,snapshot} We should not have two different error codes for the same condition. EAGAIN must be reserved for the FAULT_FLAG_ALLOW_RETRY retry case and signals to the caller that the mmap_sem has been unlocked. Use EBUSY for the !valid case so that callers can get the locking right. Link: https://lore.kernel.org/r/20190724065258.16603-2-hch@lst.de Tested-by: Ralph Campbell Signed-off-by: Christoph Hellwig Reviewed-by: Ralph Campbell Reviewed-by: Jason Gunthorpe Reviewed-by: Felix Kuehling [jgg: elaborated commit message] Signed-off-by: Jason Gunthorpe --- Documentation/vm/hmm.rst | 2 +- mm/hmm.c | 10 ++++------ 2 files changed, 5 insertions(+), 7 deletions(-) diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 7d90964abbb0..710ce1c701bf 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -237,7 +237,7 @@ The usage pattern is:: ret = hmm_range_snapshot(&range); if (ret) { up_read(&mm->mmap_sem); - if (ret == -EAGAIN) { + if (ret == -EBUSY) { /* * No need to check hmm_range_wait_until_valid() return value * on retry we will get proper error with hmm_range_snapshot() diff --git a/mm/hmm.c b/mm/hmm.c index e1eedef129cf..16b6731a34db 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -946,7 +946,7 @@ EXPORT_SYMBOL(hmm_range_unregister); * @range: range * Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid * permission (for instance asking for write and range is read only), - * -EAGAIN if you need to retry, -EFAULT invalid (ie either no valid + * -EBUSY if you need to retry, -EFAULT invalid (ie either no valid * vma or it is illegal to access that range), number of valid pages * in range->pfns[] (from range start address). * @@ -967,7 +967,7 @@ long hmm_range_snapshot(struct hmm_range *range) do { /* If range is no longer valid force retry. */ if (!range->valid) - return -EAGAIN; + return -EBUSY; vma = find_vma(hmm->mm, start); if (vma == NULL || (vma->vm_flags & device_vma)) @@ -1062,10 +1062,8 @@ long hmm_range_fault(struct hmm_range *range, bool block) do { /* If range is no longer valid force retry. */ - if (!range->valid) { - up_read(&hmm->mm->mmap_sem); - return -EAGAIN; - } + if (!range->valid) + return -EBUSY; vma = find_vma(hmm->mm, start); if (vma == NULL || (vma->vm_flags & device_vma)) -- cgit v1.2.3 From 02712bc3250849c1cf99d626aea98f610e695f34 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 24 Jul 2019 08:52:53 +0200 Subject: mm/hmm: move hmm_vma_range_done and hmm_vma_fault to nouveau These two functions are marked as a legacy APIs to get rid of, but seem to suit the current nouveau flow. Move it to the only user in preparation for fixing a locking bug involving caller and callee. All comments referring to the old API have been removed as this now is a driver private helper. Link: https://lore.kernel.org/r/20190724065258.16603-3-hch@lst.de Tested-by: Ralph Campbell Signed-off-by: Christoph Hellwig Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe --- drivers/gpu/drm/nouveau/nouveau_svm.c | 46 +++++++++++++++++++++++++++-- include/linux/hmm.h | 54 ----------------------------------- 2 files changed, 44 insertions(+), 56 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c index 8c92374afcf2..6c1b04de0db8 100644 --- a/drivers/gpu/drm/nouveau/nouveau_svm.c +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c @@ -475,6 +475,48 @@ nouveau_svm_fault_cache(struct nouveau_svm *svm, fault->inst, fault->addr, fault->access); } +static inline bool +nouveau_range_done(struct hmm_range *range) +{ + bool ret = hmm_range_valid(range); + + hmm_range_unregister(range); + return ret; +} + +static int +nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range, + bool block) +{ + long ret; + + 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)) { + up_read(&range->vma->vm_mm->mmap_sem); + return -EAGAIN; + } + + ret = hmm_range_fault(range, block); + if (ret <= 0) { + if (ret == -EBUSY || !ret) { + 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) { @@ -649,10 +691,10 @@ 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_vma_range_done(&range)) { + if (!nouveau_range_done(&range)) { mutex_unlock(&svmm->mutex); goto again; } diff --git a/include/linux/hmm.h b/include/linux/hmm.h index b8a08b2a10ca..7ef56dc18050 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -484,60 +484,6 @@ long hmm_range_dma_unmap(struct hmm_range *range, */ #define HMM_RANGE_DEFAULT_TIMEOUT 1000 -/* This is a temporary helper to avoid merge conflict between trees. */ -static inline bool hmm_vma_range_done(struct hmm_range *range) -{ - bool ret = hmm_range_valid(range); - - hmm_range_unregister(range); - return ret; -} - -/* 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) { -- cgit v1.2.3 From 5fbcf5015db8e9f04a9da6d40322622fa229da54 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 24 Jul 2019 08:52:54 +0200 Subject: nouveau: remove the block parameter to nouveau_range_fault The parameter is always false, so remove it as well as the -EAGAIN handling that can only happen for the non-blocking case. Link: https://lore.kernel.org/r/20190724065258.16603-4-hch@lst.de Tested-by: Ralph Campbell Signed-off-by: Christoph Hellwig Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe --- drivers/gpu/drm/nouveau/nouveau_svm.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c index 6c1b04de0db8..e3097492b4ad 100644 --- a/drivers/gpu/drm/nouveau/nouveau_svm.c +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c @@ -485,8 +485,7 @@ nouveau_range_done(struct hmm_range *range) } static int -nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range, - bool block) +nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range) { long ret; @@ -504,13 +503,12 @@ nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range, return -EAGAIN; } - ret = hmm_range_fault(range, block); + ret = hmm_range_fault(range, true); if (ret <= 0) { if (ret == -EBUSY || !ret) { up_read(&range->vma->vm_mm->mmap_sem); ret = -EBUSY; - } else if (ret == -EAGAIN) - ret = -EBUSY; + } hmm_range_unregister(range); return ret; } @@ -691,7 +689,7 @@ nouveau_svm_fault(struct nvif_notify *notify) range.values = nouveau_svm_pfn_values; range.pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT; again: - ret = nouveau_range_fault(&svmm->mirror, &range, true); + ret = nouveau_range_fault(&svmm->mirror, &range); if (ret == 0) { mutex_lock(&svmm->mutex); if (!nouveau_range_done(&range)) { -- cgit v1.2.3 From de4ee728465f7c0c29241550e083139b2ce9159c Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 24 Jul 2019 08:52:55 +0200 Subject: nouveau: unlock mmap_sem on all errors from nouveau_range_fault Currently nouveau_svm_fault expects nouveau_range_fault to never unlock mmap_sem, but the latter unlocks it for a random selection of error codes. Fix this up by always unlocking mmap_sem for non-zero return values in nouveau_range_fault, and only unlocking it in the caller for successful returns. Link: https://lore.kernel.org/r/20190724065258.16603-5-hch@lst.de Tested-by: Ralph Campbell Signed-off-by: Christoph Hellwig Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe --- drivers/gpu/drm/nouveau/nouveau_svm.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c index e3097492b4ad..a835cebb6d90 100644 --- a/drivers/gpu/drm/nouveau/nouveau_svm.c +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c @@ -495,8 +495,10 @@ nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range) ret = hmm_range_register(range, mirror, range->start, range->end, PAGE_SHIFT); - if (ret) + if (ret) { + up_read(&range->vma->vm_mm->mmap_sem); return (int)ret; + } if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) { up_read(&range->vma->vm_mm->mmap_sem); @@ -505,10 +507,9 @@ nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range) ret = hmm_range_fault(range, true); if (ret <= 0) { - if (ret == -EBUSY || !ret) { - up_read(&range->vma->vm_mm->mmap_sem); + if (ret == 0) ret = -EBUSY; - } + up_read(&range->vma->vm_mm->mmap_sem); hmm_range_unregister(range); return ret; } @@ -706,8 +707,8 @@ again: NULL); svmm->vmm->vmm.object.client->super = false; mutex_unlock(&svmm->mutex); + up_read(&svmm->mm->mmap_sem); } - up_read(&svmm->mm->mmap_sem); /* Cancel any faults in the window whose pages didn't manage * to keep their valid bit, or stay writeable when required. -- cgit v1.2.3