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Re: [PATCH v3 13/14] filesystem-dax: gate calls to dax_flush() on QUEUE_FLAG_WC

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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@suse.cz>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Matthew Wilcox <mawilcox@microsoft.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

...

> -	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@suse.com>
SUSE Labs, CR

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[PATCH v3 13/14] filesystem-dax: gate calls to dax_flush() on  QUEUE_FLAG_WC Dan Williams <dan.j.williams@intel.com> - 2017-06-09 22:40 +0200
  Re: [PATCH v3 13/14] filesystem-dax: gate calls to dax_flush() on  QUEUE_FLAG_WC Jan Kara <jack@suse.cz> - 2017-06-14 12:50 +0200
    Re: [PATCH v3 13/14] filesystem-dax: gate calls to dax_flush() on QUEUE_FLAG_WC Dan Williams <dan.j.williams@intel.com> - 2017-06-14 18:50 +0200
  [PATCH v4 13/14] libnvdimm,  pmem: gate cache management on QUEUE_FLAG_WC in pmem_dax_flush() Dan Williams <dan.j.williams@intel.com> - 2017-06-15 01:20 +0200
    Re: [PATCH v4 13/14] libnvdimm, pmem: gate cache management on  QUEUE_FLAG_WC in pmem_dax_flush() Jan Kara <jack@suse.cz> - 2017-06-15 10:10 +0200
  Re: [PATCH v3 13/14] filesystem-dax: gate calls to dax_flush() on         QUEUE_FLAG_WC Christoph Hellwig <hch@lst.de> - 2017-06-18 10:50 +0200
    Re: [PATCH v3 13/14] filesystem-dax: gate calls to dax_flush() on QUEUE_FLAG_WC Dan Williams <dan.j.williams@intel.com> - 2017-06-19 04:10 +0200

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