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drm/shmem_helper: Make sure PMD entries get the writeable upgrade

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Unlike PTEs which are automatically upgraded to writeable entries if
.pfn_mkwrite() returns 0, the PMD upgrades go through .huge_fault(),
and we currently pretend to have handled the make-writeable request
even though we only ever map things read-only. Make sure we pass the
proper "write" info to vmf_insert_pfn_pmd() in that case.

This also means we have to record the mkwrite event in the .huge_fault()
path now. Move the dirty tracking logic to a
drm_gem_shmem_record_mkwrite() helper so it can also be called from
drm_gem_shmem_pfn_mkwrite().

Note that this wasn't a problem before commit 28e3918179
("drm/gem-shmem: Track folio accessed/dirty status in mmap"), because
the pgprot were not lowered to read-only before this commit (see the
vma_wants_writenotify() in vma_set_page_prot()).

Fixes: 28e3918179 ("drm/gem-shmem: Track folio accessed/dirty status in mmap")
Cc: Biju Das <biju.das.jz@bp.renesas.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Reviewed-by: Loïc Molinari <loic.molinari@collabora.com>
Tested-by: Biju Das <biju.das.jz@bp.renesas.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Link: https://patch.msgid.link/20260320151914.586945-1-boris.brezillon@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
This commit is contained in:
Boris Brezillon 2026-03-20 16:19:13 +01:00
parent c636ae346d
commit cb2a2a5b37
1 changed files with 32 additions and 14 deletions
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46
drivers/gpu/drm/drm_gem_shmem_helper.c
View File

@ -554,6 +554,21 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
static void drm_gem_shmem_record_mkwrite(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct drm_gem_object *obj = vma->vm_private_data;
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
loff_t num_pages = obj->size >> PAGE_SHIFT;
pgoff_t page_offset = vmf->pgoff - vma->vm_pgoff; /* page offset within VMA */
if (drm_WARN_ON(obj->dev, !shmem->pages || page_offset >= num_pages))
return;
file_update_time(vma->vm_file);
folio_mark_dirty(page_folio(shmem->pages[page_offset]));
}
static vm_fault_t try_insert_pfn(struct vm_fault *vmf, unsigned int order,
unsigned long pfn)
{
@ -566,8 +581,23 @@ static vm_fault_t try_insert_pfn(struct vm_fault *vmf, unsigned int order,
if (aligned &&
folio_test_pmd_mappable(page_folio(pfn_to_page(pfn)))) {
vm_fault_t ret;
pfn &= PMD_MASK >> PAGE_SHIFT;
return vmf_insert_pfn_pmd(vmf, pfn, false);
/* Unlike PTEs which are automatically upgraded to
* writeable entries, the PMD upgrades go through
* .huge_fault(). Make sure we pass the "write" info
* along in that case.
* This also means we have to record the write fault
* here, instead of in .pfn_mkwrite().
*/
ret = vmf_insert_pfn_pmd(vmf, pfn,
vmf->flags & FAULT_FLAG_WRITE);
if (ret == VM_FAULT_NOPAGE && (vmf->flags & FAULT_FLAG_WRITE))
drm_gem_shmem_record_mkwrite(vmf);
return ret;
}
#endif
}
@ -655,19 +685,7 @@ static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
static vm_fault_t drm_gem_shmem_pfn_mkwrite(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct drm_gem_object *obj = vma->vm_private_data;
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
loff_t num_pages = obj->size >> PAGE_SHIFT;
pgoff_t page_offset = vmf->pgoff - vma->vm_pgoff; /* page offset within VMA */
if (drm_WARN_ON(obj->dev, !shmem->pages || page_offset >= num_pages))
return VM_FAULT_SIGBUS;
file_update_time(vma->vm_file);
folio_mark_dirty(page_folio(shmem->pages[page_offset]));
drm_gem_shmem_record_mkwrite(vmf);
return 0;
}