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From: "[email protected]" <[email protected]>
To: Damien Le Moal <[email protected]>
Cc: "[email protected]" <[email protected]>,
	Kanchan Joshi <[email protected]>, Jens Axboe <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Kanchan Joshi <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	Matthew Wilcox <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	SelvaKumar S <[email protected]>,
	Nitesh Shetty <[email protected]>,
	Javier Gonzalez <[email protected]>,
	Johannes Thumshirn <[email protected]>,
	Naohiro Aota <[email protected]>
Subject: Re: [PATCH v4 6/6] io_uring: add support for zone-append
Date: Fri, 14 Aug 2020 09:14:11 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <CY4PR04MB37517D633920E4D31AC6EA0DE74B0@CY4PR04MB3751.namprd04.prod.outlook.com>

On Wed, Aug 05, 2020 at 07:35:28AM +0000, Damien Le Moal wrote:
> > the write pointer.  The only interesting addition is that we also want
> > to report where we wrote.  So I'd rather have RWF_REPORT_OFFSET or so.
> 
> That works for me. But that rules out having the same interface for raw block
> devices since O_APPEND has no meaning in that case. So for raw block devices, it
> will have to be through zonefs. That works for me, and I think it was your idea
> all along. Can you confirm please ?

Yes.  I don't think think raw syscall level access to the zone append
primitive makes sense.  Either use zonefs for a file-like API, or
use the NVMe pass through interface for 100% raw access.

> >  - take the exclusive per-inode (zone) lock and just issue either normal
> >    writes or zone append at your choice, relying on the lock to
> >    serialize other writers.  For the async case this means we need a
> >    lock than can be release in a different context than it was acquired,
> >    which is a little ugly but can be done.
> 
> Yes, that would be possible. But likely, this will also need calls to
> inode_dio_wait() to avoid ending up with a mix of regular write and zone append
> writes in flight (which likely would result in the regular write failing as the
> zone append writes would go straight to the device without waiting for the zone
> write lock like regular writes do).

inode_dio_wait is a really bad implementation of almost a lock.  I've
started some work that I need to finish to just replace it with proper
non-owner rwsems (or even the range locks Dave has been looking into).

> 
> This all sound sensible to me. One last point though, specific to zonefs: if the
> user opens a zone file with O_APPEND, I do want to have that necessarily mean
> "use zone append". And same for the "RWF_REPORT_OFFSET". The point here is that
> both O_APPEND and RWF_REPORT_OFFSET can be used with both regular writes and
> zone append writes, but none of them actually clearly specify if the
> application/user tolerates writing data to disk in a different order than the
> issuing order... So another flag to indicate "atomic out-of-order writes" (==
> zone append) ?

O_APPEND pretty much implies out of order, as there is no way for an
application to know which thread wins the race to write the next chunk.

  reply	other threads:[~2020-08-14  8:14 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200724155244epcas5p2902f57e36e490ee8772da19aa9408cdc@epcas5p2.samsung.com>
2020-07-24 15:49 ` [PATCH v4 0/6] zone-append support in io-uring and aio Kanchan Joshi
     [not found]   ` <CGME20200724155258epcas5p1a75b926950a18cd1e6c8e7a047e6c589@epcas5p1.samsung.com>
2020-07-24 15:49     ` [PATCH v4 1/6] fs: introduce FMODE_ZONE_APPEND and IOCB_ZONE_APPEND Kanchan Joshi
2020-07-24 16:34       ` Jens Axboe
2020-07-26 15:18       ` Christoph Hellwig
2020-07-28  1:49         ` Matthew Wilcox
2020-07-28  7:26           ` Christoph Hellwig
     [not found]   ` <CGME20200724155324epcas5p18e1d3b4402d1e4a8eca87d0b56a3fa9b@epcas5p1.samsung.com>
2020-07-24 15:49     ` [PATCH v4 2/6] fs: change ki_complete interface to support 64bit ret2 Kanchan Joshi
2020-07-26 15:18       ` Christoph Hellwig
     [not found]   ` <CGME20200724155329epcas5p345ba6bad0b8fe18056bb4bcd26c10019@epcas5p3.samsung.com>
2020-07-24 15:49     ` [PATCH v4 3/6] uio: return status with iov truncation Kanchan Joshi
     [not found]   ` <CGME20200724155341epcas5p15bfc55927f2abb60f19784270fe8e377@epcas5p1.samsung.com>
2020-07-24 15:49     ` [PATCH v4 4/6] block: add zone append handling for direct I/O path Kanchan Joshi
2020-07-26 15:19       ` Christoph Hellwig
     [not found]   ` <CGME20200724155346epcas5p2cfb383fe9904a45280c6145f4c13e1b4@epcas5p2.samsung.com>
2020-07-24 15:49     ` [PATCH v4 5/6] block: enable zone-append for iov_iter of bvec type Kanchan Joshi
2020-07-26 15:20       ` Christoph Hellwig
     [not found]   ` <CGME20200724155350epcas5p3b8f1d59eda7f8fbb38c828f692d42fd6@epcas5p3.samsung.com>
2020-07-24 15:49     ` [PATCH v4 6/6] io_uring: add support for zone-append Kanchan Joshi
2020-07-24 16:29       ` Jens Axboe
2020-07-27 19:16         ` Kanchan Joshi
2020-07-27 20:34           ` Jens Axboe
2020-07-30 16:08             ` Pavel Begunkov
2020-07-30 16:13               ` Jens Axboe
2020-07-30 16:26                 ` Pavel Begunkov
2020-07-30 17:16                   ` Jens Axboe
2020-07-30 17:38                     ` Pavel Begunkov
2020-07-30 17:51                       ` Kanchan Joshi
2020-07-30 17:54                         ` Jens Axboe
2020-07-30 18:25                           ` Kanchan Joshi
2020-07-31  6:42                             ` Damien Le Moal
2020-07-31  6:45                               ` hch
2020-07-31  6:59                                 ` Damien Le Moal
2020-07-31  7:58                                   ` Kanchan Joshi
2020-07-31  8:14                                     ` Damien Le Moal
2020-07-31  9:14                                       ` hch
2020-07-31  9:34                                         ` Damien Le Moal
2020-07-31  9:41                                           ` hch
2020-07-31 10:16                                             ` Damien Le Moal
2020-07-31 12:51                                               ` hch
2020-07-31 13:08                                                 ` hch
2020-07-31 15:07                                                   ` Kanchan Joshi
2022-03-02 20:47                                                   ` Luis Chamberlain
2020-08-05  7:35                                                 ` Damien Le Moal
2020-08-14  8:14                                                   ` hch [this message]
2020-08-14  8:27                                                     ` Damien Le Moal
2020-08-14 12:04                                                       ` hch
2020-08-14 12:20                                                         ` Damien Le Moal
2020-09-07  7:01                                                     ` Kanchan Joshi
2020-09-08 15:18                                                       ` hch
2020-09-24 17:19                                                         ` Kanchan Joshi
2020-09-25  2:52                                                           ` Damien Le Moal
2020-09-28 18:58                                                             ` Kanchan Joshi
2020-09-29  1:24                                                               ` Damien Le Moal
2020-09-29 18:49                                                                 ` Kanchan Joshi
2022-03-02 20:43                                                         ` Luis Chamberlain
2020-07-31  9:38                                       ` Kanchan Joshi
2022-03-02 20:51                                 ` Luis Chamberlain
2020-07-31  7:08                               ` Kanchan Joshi
2020-07-30 15:57       ` Pavel Begunkov

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