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 <[email protected]>
> Cc: Jeff Moyer <[email protected]>
> Cc: Christoph Hellwig <[email protected]>
> Cc: Matthew Wilcox <[email protected]>
> Cc: Ross Zwisler <[email protected]>
> Signed-off-by: Dan Williams <[email protected]>
...
> - 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 <[email protected]>
SUSE Labs, CR
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