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From: David Howells <dhowells@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: dhowells@redhat.com, Carlos Maiolino <cmaiolino@redhat.com>,
	linux-fsdevel@vger.kernel.org, adilger@dilger.ca,
	jaegeuk@kernel.org, darrick.wong@oracle.com, miklos@szeredi.hu,
	rpeterso@redhat.com, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 2/9] cachefiles: drop direct usage of ->bmap method.
Date: Fri, 30 Aug 2019 17:17:51 +0100	[thread overview]
Message-ID: <2587.1567181871@warthog.procyon.org.uk> (raw)
In-Reply-To: <20190829071312.GE11909@lst.de>

Christoph Hellwig <hch@lst.de> wrote:

> Not related to this patch, but using iov_iter with dio is trivial, what
> is the blocker therere?

The usual: time.

The change as a whole is not actually trivial since it will involve completely
overhauling the fscache data API and how the filesystems use it - and then
having cachefiles perform the DIO asynchronously as per Trond's requirements
for using fscache with NFS.

I also need to work out how I'm going to do data/hole detection.  Can I set,
say, O_NOREADHOLE and then expect the DIO to stop early with a short read?  Or
do I need to use SEEK_DATA/SEEK_HOLE in advance to define the occupied
regions?

Maybe a better way would be to take a leaf out of the book of OpenAFS and
suchlike and keep a parallel file that tracks the occupancy of a cache object
(eg. a bitmap with 1 bit per 64k block) - but that the synchronisation and
performance issues.

David

  parent reply	other threads:[~2019-08-30 16:17 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-08  8:27 [PATCH 0/9 V5] New ->fiemap infrastructure and ->bmap removal Carlos Maiolino
2019-08-08  8:27 ` [PATCH 1/9] fs: Enable bmap() function to properly return errors Carlos Maiolino
2019-08-08 21:24   ` kbuild test robot
2019-08-14 11:14   ` Christoph Hellwig
2019-08-20 11:36     ` Carlos Maiolino
2019-08-08  8:27 ` [PATCH 2/9] cachefiles: drop direct usage of ->bmap method Carlos Maiolino
2019-08-14 11:15   ` Christoph Hellwig
2019-08-20 11:57     ` Carlos Maiolino
2019-08-20 12:50     ` David Howells
2019-08-29  7:13       ` Christoph Hellwig
2019-08-30 16:17       ` David Howells [this message]
2019-08-30 16:59         ` Christoph Hellwig
2019-08-31  0:45         ` David Howells
2019-09-05 22:44           ` Dave Chinner
2019-08-20 13:31   ` David Howells
2019-08-08  8:27 ` [PATCH 3/9] ecryptfs: drop direct calls to ->bmap Carlos Maiolino
2019-08-08 22:50   ` kbuild test robot
2019-08-08  8:27 ` [PATCH 4/9] fibmap: Use bmap instead of ->bmap method in ioctl_fibmap Carlos Maiolino
2019-08-08 20:38   ` kbuild test robot
2019-08-14 11:01     ` Carlos Maiolino
2019-08-14 11:08       ` Christoph Hellwig
2019-08-08  8:27 ` [PATCH 5/9] fs: Move start and length fiemap fields into fiemap_extent_info Carlos Maiolino
2019-08-08 20:21   ` kbuild test robot
2019-08-08  8:27 ` [PATCH 6/9] iomap: Remove length and start fields from iomap_fiemap Carlos Maiolino
2019-08-08  8:27 ` [PATCH 7/9] fiemap: Use a callback to fill fiemap extents Carlos Maiolino
2019-08-09  0:04   ` kbuild test robot
2019-08-14 11:16   ` Christoph Hellwig
2019-08-08  8:27 ` [PATCH 8/9] Use FIEMAP for FIBMAP calls Carlos Maiolino
2019-08-09  1:56   ` kbuild test robot
2019-08-14 11:18   ` Christoph Hellwig
2019-08-20 13:01     ` Carlos Maiolino
2019-08-29  7:15       ` Christoph Hellwig
2019-09-10 12:28         ` Carlos Maiolino
2019-09-16 15:58           ` Darrick J. Wong
2019-08-08  8:27 ` [PATCH 9/9] xfs: Get rid of ->bmap Carlos Maiolino
  -- strict thread matches above, loose matches on Subject: below --
2019-09-11 13:43 [PATCH 0/9 V6] New ->fiemap infrastructure and ->bmap removal Carlos Maiolino
2019-09-11 13:43 ` [PATCH 2/9] cachefiles: drop direct usage of ->bmap method Carlos Maiolino
2019-07-31 14:12 [PATCH 0/9 V4] New ->fiemap infrastructure and ->bmap removal Carlos Maiolino
2019-07-31 14:12 ` [PATCH 2/9] cachefiles: drop direct usage of ->bmap method Carlos Maiolino
2019-02-18 13:03 [PATCH 0/9 V3] New ->fiemap infrastructure and ->bmap removal Carlos Maiolino
2019-02-18 13:03 ` [PATCH 2/9] cachefiles: drop direct usage of ->bmap method Carlos Maiolino

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