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mm: introduce vma_set_file function v4
Add the new vma_set_file() function to allow changing vma->vm_file with the necessary refcount dance. v2: add more users of this. v3: add missing EXPORT_SYMBOL, rebase on mmap cleanup, add comments why we drop the reference on two occasions. v4: make it clear that changing an anonymous vma is illegal. Signed-off-by: Christian König <christian.koenig@amd.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v2) Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Link: https://patchwork.freedesktop.org/patch/394773/
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@ -1183,8 +1183,7 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
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return -EINVAL;
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/* readjust the vma */
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fput(vma->vm_file);
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vma->vm_file = get_file(dmabuf->file);
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vma_set_file(vma, dmabuf->file);
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vma->vm_pgoff = pgoff;
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return dmabuf->ops->mmap(dmabuf, vma);
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@ -145,10 +145,8 @@ static int etnaviv_gem_mmap_obj(struct etnaviv_gem_object *etnaviv_obj,
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* address_space (so unmap_mapping_range does what we want,
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* in particular in the case of mmap'd dmabufs)
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*/
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fput(vma->vm_file);
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get_file(etnaviv_obj->base.filp);
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vma->vm_pgoff = 0;
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vma->vm_file = etnaviv_obj->base.filp;
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vma_set_file(vma, etnaviv_obj->base.filp);
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vma->vm_page_prot = vm_page_prot;
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}
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@ -114,8 +114,7 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *
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if (ret)
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return ret;
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fput(vma->vm_file);
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vma->vm_file = get_file(obj->base.filp);
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vma_set_file(vma, obj->base.filp);
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return 0;
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}
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@ -893,8 +893,9 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
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* requires avoiding extraneous references to their filp, hence why
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* we prefer to use an anonymous file for their mmaps.
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*/
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fput(vma->vm_file);
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vma->vm_file = anon;
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vma_set_file(vma, anon);
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/* Drop the initial creation reference, the vma is now holding one. */
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fput(anon);
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switch (mmo->mmap_type) {
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case I915_MMAP_TYPE_WC:
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@ -212,10 +212,8 @@ int msm_gem_mmap_obj(struct drm_gem_object *obj,
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* address_space (so unmap_mapping_range does what we want,
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* in particular in the case of mmap'd dmabufs)
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*/
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fput(vma->vm_file);
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get_file(obj->filp);
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vma->vm_pgoff = 0;
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vma->vm_file = obj->filp;
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vma_set_file(vma, obj->filp);
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vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
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}
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@ -564,9 +564,8 @@ int omap_gem_mmap_obj(struct drm_gem_object *obj,
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* address_space (so unmap_mapping_range does what we want,
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* in particular in the case of mmap'd dmabufs)
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*/
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fput(vma->vm_file);
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vma->vm_pgoff = 0;
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vma->vm_file = get_file(obj->filp);
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vma_set_file(vma, obj->filp);
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vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
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}
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@ -397,8 +397,7 @@ static int vgem_prime_mmap(struct drm_gem_object *obj,
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if (ret)
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return ret;
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fput(vma->vm_file);
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vma->vm_file = get_file(obj->filp);
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vma_set_file(vma, obj->filp);
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vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
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vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
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@ -450,9 +450,9 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
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vma_set_anonymous(vma);
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}
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if (vma->vm_file)
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fput(vma->vm_file);
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vma->vm_file = asma->file;
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vma_set_file(vma, asma->file);
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/* XXX: merge this with the get_file() above if possible */
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fput(asma->file);
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out:
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mutex_unlock(&ashmem_mutex);
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@ -2719,6 +2719,8 @@ static inline void vma_set_page_prot(struct vm_area_struct *vma)
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}
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#endif
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void vma_set_file(struct vm_area_struct *vma, struct file *file);
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#ifdef CONFIG_NUMA_BALANCING
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unsigned long change_prot_numa(struct vm_area_struct *vma,
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unsigned long start, unsigned long end);
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12
mm/mmap.c
12
mm/mmap.c
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@ -136,6 +136,18 @@ void vma_set_page_prot(struct vm_area_struct *vma)
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WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
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}
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/*
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* Change backing file, only valid to use during initial VMA setup.
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*/
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void vma_set_file(struct vm_area_struct *vma, struct file *file)
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{
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/* Changing an anonymous vma with this is illegal */
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get_file(file);
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swap(vma->vm_file, file);
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fput(file);
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}
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EXPORT_SYMBOL(vma_set_file);
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/*
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* Requires inode->i_mapping->i_mmap_rwsem
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*/
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