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mm: introduce vma_set_file function v4

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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/
This commit is contained in:
Christian König
2020-09-14 15:09:33 +02:00
parent 0227da01f2
commit 2b5b95b1ff
10 changed files with 26 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/dma-buf/dma-buf.c
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@@ -1183,8 +1183,7 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
return -EINVAL; return -EINVAL;
/* readjust the vma */ /* readjust the vma */
fput(vma->vm_file); vma_set_file(vma, dmabuf->file);
vma->vm_file = get_file(dmabuf->file);
vma->vm_pgoff = pgoff; vma->vm_pgoff = pgoff;
return dmabuf->ops->mmap(dmabuf, vma); return dmabuf->ops->mmap(dmabuf, vma);

4
drivers/gpu/drm/etnaviv/etnaviv_gem.c
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@@ -145,10 +145,8 @@ static int etnaviv_gem_mmap_obj(struct etnaviv_gem_object *etnaviv_obj,
* address_space (so unmap_mapping_range does what we want, * address_space (so unmap_mapping_range does what we want,
* in particular in the case of mmap'd dmabufs) * in particular in the case of mmap'd dmabufs)
*/ */
fput(vma->vm_file);
get_file(etnaviv_obj->base.filp);
vma->vm_pgoff = 0; vma->vm_pgoff = 0;
vma->vm_file = etnaviv_obj->base.filp; vma_set_file(vma, etnaviv_obj->base.filp);
vma->vm_page_prot = vm_page_prot; vma->vm_page_prot = vm_page_prot;
} }

3
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
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@@ -114,8 +114,7 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *
if (ret) if (ret)
return ret; return ret;
fput(vma->vm_file); vma_set_file(vma, obj->base.filp);
vma->vm_file = get_file(obj->base.filp);
return 0; return 0;
} }

5
drivers/gpu/drm/i915/gem/i915_gem_mman.c
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@@ -893,8 +893,9 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
* requires avoiding extraneous references to their filp, hence why * requires avoiding extraneous references to their filp, hence why
* we prefer to use an anonymous file for their mmaps. * we prefer to use an anonymous file for their mmaps.
*/ */
fput(vma->vm_file); vma_set_file(vma, anon);
vma->vm_file = anon; /* Drop the initial creation reference, the vma is now holding one. */
fput(anon);
switch (mmo->mmap_type) { switch (mmo->mmap_type) {
case I915_MMAP_TYPE_WC: case I915_MMAP_TYPE_WC:

4
drivers/gpu/drm/msm/msm_gem.c
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@@ -212,10 +212,8 @@ int msm_gem_mmap_obj(struct drm_gem_object *obj,
* address_space (so unmap_mapping_range does what we want, * address_space (so unmap_mapping_range does what we want,
* in particular in the case of mmap'd dmabufs) * in particular in the case of mmap'd dmabufs)
*/ */
fput(vma->vm_file);
get_file(obj->filp);
vma->vm_pgoff = 0; vma->vm_pgoff = 0;
vma->vm_file = obj->filp; vma_set_file(vma, obj->filp);
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
} }

3
drivers/gpu/drm/omapdrm/omap_gem.c
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@@ -564,9 +564,8 @@ int omap_gem_mmap_obj(struct drm_gem_object *obj,
* address_space (so unmap_mapping_range does what we want, * address_space (so unmap_mapping_range does what we want,
* in particular in the case of mmap'd dmabufs) * in particular in the case of mmap'd dmabufs)
*/ */
fput(vma->vm_file);
vma->vm_pgoff = 0; vma->vm_pgoff = 0;
vma->vm_file = get_file(obj->filp); vma_set_file(vma, obj->filp);
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
} }

3
drivers/gpu/drm/vgem/vgem_drv.c
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@@ -397,8 +397,7 @@ static int vgem_prime_mmap(struct drm_gem_object *obj,
if (ret) if (ret)
return ret; return ret;
fput(vma->vm_file); vma_set_file(vma, obj->filp);
vma->vm_file = get_file(obj->filp);
vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP; vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags)); vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

6
drivers/staging/android/ashmem.c
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@@ -450,9 +450,9 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
vma_set_anonymous(vma); vma_set_anonymous(vma);
} }
if (vma->vm_file) vma_set_file(vma, asma->file);
fput(vma->vm_file); /* XXX: merge this with the get_file() above if possible */
vma->vm_file = asma->file; fput(asma->file);
out: out:
mutex_unlock(&ashmem_mutex); mutex_unlock(&ashmem_mutex);

2
include/linux/mm.h
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@@ -2719,6 +2719,8 @@ static inline void vma_set_page_prot(struct vm_area_struct *vma)
} }
#endif #endif
void vma_set_file(struct vm_area_struct *vma, struct file *file);
#ifdef CONFIG_NUMA_BALANCING #ifdef CONFIG_NUMA_BALANCING
unsigned long change_prot_numa(struct vm_area_struct *vma, unsigned long change_prot_numa(struct vm_area_struct *vma,
unsigned long start, unsigned long end); unsigned long start, unsigned long end);

12
mm/mmap.c
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@@ -136,6 +136,18 @@ void vma_set_page_prot(struct vm_area_struct *vma)
WRITE_ONCE(vma->vm_page_prot, vm_page_prot); WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
} }
/*
* Change backing file, only valid to use during initial VMA setup.
*/
void vma_set_file(struct vm_area_struct *vma, struct file *file)
{
/* Changing an anonymous vma with this is illegal */
get_file(file);
swap(vma->vm_file, file);
fput(file);
}
EXPORT_SYMBOL(vma_set_file);
/* /*
* Requires inode->i_mapping->i_mmap_rwsem * Requires inode->i_mapping->i_mmap_rwsem
*/ */