On Fri 09-06-17 13:24:56, Dan Williams wrote: > Some platforms arrange for cpu caches to be flushed on power-fail. On > those platforms there is no requirement that the kernel track and flush > potentially dirty cache lines. Given that we still insert entries into > the radix for locking purposes this patch only disables the cache flush > loop, not the dirty tracking. > > Userspace can override the default cache setting via the block device > queue "write_cache" attribute in sysfs. > > Cc: Jan Kara <jack@xxxxxxx> > Cc: Jeff Moyer <jmoyer@xxxxxxxxxx> > Cc: Christoph Hellwig <hch@xxxxxx> > Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> > Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> ... > - dax_flush(dax_dev, pgoff, kaddr, size); > + if (test_bit(QUEUE_FLAG_WC, &bdev->bd_queue->queue_flags)) > + dax_flush(dax_dev, pgoff, kaddr, size); IMHO the check belongs into dax_flush() similarly as blkdev_issue_flush() takes silently handles whether the flush is actually needed or not. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
