From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> [ Upstream commit aa56a292ce623734ddd30f52d73f527d1f3529b5 ] set_page_dirty says: For pages with a mapping this should be done under the page lock for the benefit of asynchronous memory errors who prefer a consistent dirty state. This rule can be broken in some special cases, but should be better not to. Under those rules, it is only safe for us to use the plain set_page_dirty calls for shmemfs/anonymous memory. Userptr may be used with real mappings and so needs to use the locked version (set_page_dirty_lock). Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203317 Fixes: 5cc9ed4b9a7a ("drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl") References: 6dcc693bc57f ("ext4: warn when page is dirtied without buffers") Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20190708140327.26825-1-chris@xxxxxxxxxxxxxxxxxx (cherry picked from commit cb6d7c7dc7ff8cace666ddec66334117a6068ce2) Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/gpu/drm/i915/i915_gem_userptr.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c index 8079ea3af1039..b1fc15c7f5997 100644 --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -678,7 +678,15 @@ i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj, for_each_sgt_page(page, sgt_iter, pages) { if (obj->mm.dirty) - set_page_dirty(page); + /* + * As this may not be anonymous memory (e.g. shmem) + * but exist on a real mapping, we have to lock + * the page in order to dirty it -- holding + * the page reference is not sufficient to + * prevent the inode from being truncated. + * Play safe and take the lock. + */ + set_page_dirty_lock(page); mark_page_accessed(page); put_page(page); -- 2.20.1
