Chris Wilson 0d4bbe3d40 drm/i915/userptr: Try to acquire the page lock around set_page_dirty() ... 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). However, following a try_to_unmap() we may want to remove the userptr and so call put_pages(). However, try_to_unmap() acquires the page lock and so we must avoid recursively locking the pages ourselves -- which means that we cannot safely acquire the lock around set_page_dirty(). Since we can't be sure of the lock, we have to risk skip dirtying the page, or else risk calling set_page_dirty() without a lock and so risk fs corruption. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203317 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112012 Fixes: 5cc9ed4b9a ("drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl") References: cb6d7c7dc7 ("drm/i915/userptr: Acquire the page lock around set_page_dirty()") References: 505a8ec7e1 ("Revert "drm/i915/userptr: Acquire the page lock around set_page_dirty()"") References: 6dcc693bc5 ("ext4: warn when page is dirtied without buffers") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: stable@vger.kernel.org Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191111133205.11590-1-chris@chris-wilson.co.uk		2019-11-11 15:44:25 +00:00
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drm	drm/i915/userptr: Try to acquire the page lock around set_page_dirty()	2019-11-11 15:44:25 +00:00
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