mm: introduce vma_set_file function v5
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. v5: move vma_set_file to mm/util.c 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> Acked-by: Andrew Morton <akpm@linux-foundation.org> Link: https://patchwork.freedesktop.org/patch/399360/ Signed-off-by: Juhyung Park <qkrwngud825@gmail.com> Change-Id: If77ffac122fac2da1ec34b886784381c4648b2c5
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@ -1213,8 +1213,7 @@ 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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@ -232,10 +232,8 @@ 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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@ -449,9 +449,9 @@ 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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@ -2573,6 +2573,8 @@ 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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13
mm/util.c
13
mm/util.c
@ -4,6 +4,7 @@
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#include <linux/compiler.h>
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#include <linux/export.h>
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#include <linux/err.h>
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#include <linux/file.h>
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#include <linux/sched.h>
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#include <linux/sched/mm.h>
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#include <linux/sched/task_stack.h>
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@ -329,6 +330,18 @@ unsigned long randomize_page(unsigned long start, unsigned long range)
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return start + (get_random_long() % range << PAGE_SHIFT);
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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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#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
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void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
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{
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