Messages in this thread | | | Subject | Re: [PATCH 1/4] mm: introduce vma_set_file function v2 | From | Christian König <> | Date | Fri, 9 Oct 2020 09:16:49 +0200 |
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Am 08.10.20 um 16:12 schrieb Daniel Vetter: > On Thu, Oct 08, 2020 at 01:23:39PM +0200, Christian König wrote: >> Add the new vma_set_file() function to allow changing >> vma->vm_file with the necessary refcount dance. >> >> v2: add more users of this. >> >> Signed-off-by: Christian König <christian.koenig@amd.com> >> --- >> drivers/dma-buf/dma-buf.c | 16 +++++----------- >> drivers/gpu/drm/etnaviv/etnaviv_gem.c | 4 +--- >> drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 3 +-- >> drivers/gpu/drm/i915/gem/i915_gem_mman.c | 4 ++-- >> drivers/gpu/drm/msm/msm_gem.c | 4 +--- >> drivers/gpu/drm/omapdrm/omap_gem.c | 3 +-- >> drivers/gpu/drm/vgem/vgem_drv.c | 3 +-- >> drivers/staging/android/ashmem.c | 5 ++--- >> include/linux/mm.h | 2 ++ >> mm/mmap.c | 16 ++++++++++++++++ >> 10 files changed, 32 insertions(+), 28 deletions(-) >> >> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c >> index a6ba4d598f0e..e4316aa7e0f4 100644 >> --- a/drivers/dma-buf/dma-buf.c >> +++ b/drivers/dma-buf/dma-buf.c >> @@ -1163,20 +1163,14 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, >> return -EINVAL; >> >> /* readjust the vma */ >> - get_file(dmabuf->file); >> - oldfile = vma->vm_file; >> - vma->vm_file = dmabuf->file; >> + oldfile = vma_set_file(vma, dmabuf->file); >> vma->vm_pgoff = pgoff; >> >> ret = dmabuf->ops->mmap(dmabuf, vma); >> - if (ret) { >> - /* restore old parameters on failure */ >> - vma->vm_file = oldfile; >> - fput(dmabuf->file); >> - } else { >> - if (oldfile) >> - fput(oldfile); >> - } >> + /* restore old parameters on failure */ >> + if (ret) >> + vma_set_file(vma, oldfile); > I think these two lines here are cargo-cult: If this fails, the mmap fails > and therefore the vma structure is kfreed. No point at all in restoring > anything.
This was explicitly added with this patch to fix a problem:
commit 495c10cc1c0c359871d5bef32dd173252fc17995 Author: John Sheu <sheu@google.com> Date: Mon Feb 11 17:50:24 2013 -0800
CHROMIUM: dma-buf: restore args on failure of dma_buf_mmap
Callers to dma_buf_mmap expect to fput() the vma struct's vm_file themselves on failure. Not restoring the struct's data on failure causes a double-decrement of the vm_file's refcount.
> With that: Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Can I keep that even with the error handling working? :)
Christian.
> >> + >> return ret; >> >> } >> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c >> index 312e9d58d5a7..10ce267c0947 100644 >> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c >> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c >> @@ -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, >> * 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_file = etnaviv_obj->base.filp; >> + vma_set_file(vma, etnaviv_obj->base.filp); >> >> vma->vm_page_prot = vm_page_prot; >> } >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c >> index fec0e1e3dc3e..8ce4c9e28b87 100644 >> --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c >> @@ -119,8 +119,7 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct * >> if (ret) >> return ret; >> >> - fput(vma->vm_file); >> - vma->vm_file = get_file(obj->base.filp); >> + vma_set_file(vma, obj->base.filp); >> >> return 0; >> } >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c >> index 3d69e51f3e4d..c9d5f1a38af3 100644 >> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c >> @@ -893,8 +893,8 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma) >> * requires avoiding extraneous references to their filp, hence why >> * we prefer to use an anonymous file for their mmaps. >> */ >> - fput(vma->vm_file); >> - vma->vm_file = anon; >> + vma_set_file(vma, anon); >> + fput(anon); >> >> switch (mmo->mmap_type) { >> case I915_MMAP_TYPE_WC: >> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c >> index de915ff6f4b4..a71f42870d5e 100644 >> --- a/drivers/gpu/drm/msm/msm_gem.c >> +++ b/drivers/gpu/drm/msm/msm_gem.c >> @@ -223,10 +223,8 @@ int msm_gem_mmap_obj(struct drm_gem_object *obj, >> * address_space (so unmap_mapping_range does what we want, >> * in particular in the case of mmap'd dmabufs) >> */ >> - fput(vma->vm_file); >> - get_file(obj->filp); >> 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); >> } >> diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c >> index 979d53a93c2b..0d4542ff1d7d 100644 >> --- a/drivers/gpu/drm/omapdrm/omap_gem.c >> +++ b/drivers/gpu/drm/omapdrm/omap_gem.c >> @@ -564,9 +564,8 @@ int omap_gem_mmap_obj(struct drm_gem_object *obj, >> * address_space (so unmap_mapping_range does what we want, >> * in particular in the case of mmap'd dmabufs) >> */ >> - fput(vma->vm_file); >> 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); >> } >> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c >> index fa54a6d1403d..ea0eecae5153 100644 >> --- a/drivers/gpu/drm/vgem/vgem_drv.c >> +++ b/drivers/gpu/drm/vgem/vgem_drv.c >> @@ -397,8 +397,7 @@ static int vgem_prime_mmap(struct drm_gem_object *obj, >> if (ret) >> return ret; >> >> - fput(vma->vm_file); >> - vma->vm_file = get_file(obj->filp); >> + vma_set_file(vma, obj->filp); >> vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP; >> vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags)); >> >> diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c >> index 10b4be1f3e78..a51dc089896e 100644 >> --- a/drivers/staging/android/ashmem.c >> +++ b/drivers/staging/android/ashmem.c >> @@ -450,9 +450,8 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) >> vma_set_anonymous(vma); >> } >> >> - if (vma->vm_file) >> - fput(vma->vm_file); >> - vma->vm_file = asma->file; >> + vma_set_file(vma, asma->file); >> + fput(asma->file); >> >> out: >> mutex_unlock(&ashmem_mutex); >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index ca6e6a81576b..a558602afe1b 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -2693,6 +2693,8 @@ static inline void vma_set_page_prot(struct vm_area_struct *vma) >> } >> #endif >> >> +struct file *vma_set_file(struct vm_area_struct *vma, struct file *file); >> + >> #ifdef CONFIG_NUMA_BALANCING >> unsigned long change_prot_numa(struct vm_area_struct *vma, >> unsigned long start, unsigned long end); >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 40248d84ad5f..d3c3c510f643 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -136,6 +136,22 @@ void vma_set_page_prot(struct vm_area_struct *vma) >> WRITE_ONCE(vma->vm_page_prot, vm_page_prot); >> } >> >> +/* >> + * Change backing file, only valid to use during initial VMA setup. >> + */ >> +struct file *vma_set_file(struct vm_area_struct *vma, struct file *file) >> +{ >> + if (file) >> + get_file(file); >> + >> + swap(vma->vm_file, file); >> + >> + if (file) >> + fput(file); >> + >> + return file; >> +} >> + >> /* >> * Requires inode->i_mapping->i_mmap_rwsem >> */ >> -- >> 2.17.1 >>
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