Merge tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux
fix 1 mysterious divide error
fix 3 NULL dereference bugs in writeback tracing, on SD card removal w/o umount
* tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux:
writeback: fix dereferencing NULL bdi->dev on trace_writeback_queue
lib: proportion: lower PROP_MAX_SHIFT to 32 on 64-bit kernel
writeback: fix NULL bdi->dev in trace writeback_single_inode
backing-dev: fix wakeup timer races with bdi_unregister()
