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From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Mike Snitzer <snitzer@redhat.com>,
	Matthew Wilcox <mawilcox@microsoft.com>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	linux-block@vger.kernel.org,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [RFC PATCH 10/17] block: introduce bdev_dax_direct_access()
Date: Wed, 1 Feb 2017 09:10:20 +0100	[thread overview]
Message-ID: <20170201081020.GD29170@lst.de> (raw)
In-Reply-To: <CAPcyv4iARmZQSBybJ1iJhwkndVxSe62rk4hjP1T9prBuOqVQ-A@mail.gmail.com>

On Mon, Jan 30, 2017 at 10:16:29AM -0800, Dan Williams wrote:
> Ok, now that dax_map_atomic() is gone, it's much easier to remove
> struct blk_dax_ctl.
> 
> We can also move the partition alignment checks to be a one-time check
> at bdev_dax_capable() time and kill bdev_dax_direct_access() in favor
> of calling dax_direct_access() directly.

Yes, please.

> >> +     if ((sector + DIV_ROUND_UP(dax->size, 512))
> >> +                     > part_nr_sects_read(bdev->bd_part))
> >> +             return -ERANGE;
> >> +     sector += get_start_sect(bdev);
> >> +     return dax_direct_access(dax_inode, sector * 512, &dax->addr,
> >> +                     &dax->pfn, dax->size);
> >
> > And please switch to using bytes as the granularity given that we're
> > deadling with byte addressable memory.
> 
> dax_direct_access() does take a byte aligned physical address, but it
> needs to be at least page aligned since we are returning a pfn_t...
> 
> Hmm, perhaps the input should be raw page frame number. We could
> reduce one of the arguments by making the current 'pfn_t *' parameter
> an in/out-parameter.

In/Out parameters are always a bit problematic in terms of API clarity.
And updating a device-relative address with an absolute physical one
sounds like an odd API for sure.
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  reply	other threads:[~2017-02-01  8:10 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-28  8:36 [RFC PATCH 00/17] introduce a dax_inode for dax_operations Dan Williams
2017-01-28  8:36 ` [RFC PATCH 01/17] dax: refactor dax-fs into a generic provider of dax inodes Dan Williams
2017-01-30 12:28   ` Christoph Hellwig
2017-01-30 17:12     ` Dan Williams
2017-01-28  8:36 ` [RFC PATCH 02/17] dax: convert dax_inode locking to srcu Dan Williams
2017-01-28  8:36 ` [RFC PATCH 03/17] dax: add a facility to lookup a dax inode by 'host' device name Dan Williams
2017-01-28  8:36 ` [RFC PATCH 04/17] dax: introduce dax_operations Dan Williams
2017-01-28  8:36 ` [RFC PATCH 05/17] pmem: add dax_operations support Dan Williams
2017-01-28  8:36 ` [RFC PATCH 06/17] axon_ram: " Dan Williams
2017-01-28  8:36 ` [RFC PATCH 07/17] brd: " Dan Williams
2017-01-28  8:36 ` [RFC PATCH 08/17] dcssblk: " Dan Williams
2017-01-28  8:36 ` [RFC PATCH 09/17] block: kill bdev_dax_capable() Dan Williams
2017-01-28  8:36 ` [RFC PATCH 10/17] block: introduce bdev_dax_direct_access() Dan Williams
2017-01-30 12:32   ` Christoph Hellwig
2017-01-30 18:16     ` Dan Williams
2017-02-01  8:10       ` Christoph Hellwig [this message]
2017-02-01  9:21         ` Dan Williams
2017-02-01  9:28           ` Christoph Hellwig
2017-01-28  8:37 ` [RFC PATCH 11/17] dm: add dax_operations support (producer) Dan Williams
2017-01-28  8:37 ` [RFC PATCH 12/17] dm: add dax_operations support (consumer) Dan Williams
2017-01-28  8:37 ` [RFC PATCH 13/17] fs: update mount_bdev() to lookup dax infrastructure Dan Williams
2017-01-30 12:26   ` Christoph Hellwig
2017-01-30 18:29     ` Dan Williams
2017-02-01  8:08       ` Christoph Hellwig
2017-02-01  9:16         ` Dan Williams
2017-01-28  8:37 ` [RFC PATCH 14/17] ext2, ext4, xfs: retrieve dax_inode through iomap operations Dan Williams
2017-01-28  8:37 ` [RFC PATCH 15/17] Revert "block: use DAX for partition table reads" Dan Williams
2017-01-28  8:37 ` [RFC PATCH 16/17] fs, dax: convert filesystem-dax to bdev_dax_direct_access Dan Williams
2017-01-28  8:37 ` [RFC PATCH 17/17] block: remove block_device_operations.direct_access and related infrastructure Dan Williams

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