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From: Mike Snitzer <snitzer@kernel.org>
To: Joe Thornber <thornber@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Darrick J. Wong" <djwong@kernel.org>,
	Brian Foster <bfoster@redhat.com>,
	Bart Van Assche <bvanassche@google.com>,
	linux-kernel@vger.kernel.org, Joe Thornber <ejt@redhat.com>,
	Christoph Hellwig <hch@infradead.org>,
	dm-devel@redhat.com, Andreas Dilger <adilger.kernel@dilger.ca>,
	Sarthak Kukreti <sarthakkukreti@chromium.org>,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	Jason Wang <jasowang@redhat.com>,
	Alasdair Kergon <agk@redhat.com>
Subject: Re: [PATCH v7 0/5] Introduce provisioning primitives
Date: Tue, 30 May 2023 10:02:39 -0400	[thread overview]
Message-ID: <ZHYB/6l5Wi+xwkbQ@redhat.com> (raw)
In-Reply-To: <CAJ0trDZJQwvAzngZLBJ1hB0XkQ1HRHQOdNQNTw9nK-U5i-0bLA@mail.gmail.com>

On Tue, May 30 2023 at  3:27P -0400,
Joe Thornber <thornber@redhat.com> wrote:

> On Sat, May 27, 2023 at 12:45 AM Dave Chinner <david@fromorbit.com> wrote:
> 
> > On Fri, May 26, 2023 at 12:04:02PM +0100, Joe Thornber wrote:
> >
> > > 1) We have an api (ioctl, bio flag, whatever) that lets you
> > > reserve/guarantee a region:
> > >
> > >   int reserve_region(dev, sector_t begin, sector_t end);
> >
> > A C-based interface is not sufficient because the layer that must do
> > provsioning is not guaranteed to be directly under the filesystem.
> > We must be able to propagate the request down to the layers that
> > need to provision storage, and that includes hardware devices.
> >
> > e.g. dm-thin would have to issue REQ_PROVISION on the LBA ranges it
> > allocates in it's backing device to guarantee that the provisioned
> > LBA range it allocates is also fully provisioned by the storage
> > below it....
> >
> 
> Fine, bio flag it is.
> 
> 
> >
> > >   This api should be used minimally, eg, critical FS metadata only.
> >
> >
> >
> > Plan for having to support tens of GBs of provisioned space in
> > filesystems, not tens of MBs....
> >
> 
> Also fine.
> 
> 
> I think there's a 2-3 solid days of coding to fully implement
> > REQ_PROVISION support in XFS, including userspace tool support.
> > Maybe a couple of weeks more to flush the bugs out before it's
> > largely ready to go.
> >
> > So if there's buy in from the block layer and DM people for
> > REQ_PROVISION as described, then I'll definitely have XFS support
> > ready for you to test whenever dm-thinp is ready to go.
> >
> 
> Great, this is what I wanted to hear.  I guess we need an ack from the
> block guys and then I'll get started.

The block portion is where this discussion started (in the context of
this thread's patchset, now at v7).

During our discussion I think there were 2 gaps identified with this
patchset:

1) provisioning should be opt-in, and we need a clear flag that upper
   layers look for to know if REQ_PROVISION available
   - we do get this with the max_provision_sectors = 0 default, is
     checking queue_limits (via queue_max_provision_sectors)
     sufficient for upper layers like xfs?

2) DM thinp needs REQ_PROVISION passdown support
   - also dm_table_supports_provision() needs to be stricter by
     requiring _all_ underlying devices support provisioning?

Bonus dm-thinp work: add ranged REQ_PROVISION support to reduce number
of calls (and bios) block core needs to pass to dm thinp.

Also Joe, for you proposed dm-thinp design where you distinquish
between "provision" and "reserve": Would it make sense for REQ_META
(e.g. all XFS metadata) with REQ_PROVISION to be treated as an
LBA-specific hard request?  Whereas REQ_PROVISION on its own provides
more freedom to just reserve the length of blocks? (e.g. for XFS
delalloc where LBA range is unknown, but dm-thinp can be asked to
reserve space to accomodate it).

Mike

  parent reply	other threads:[~2023-05-30 14:03 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-18 22:33 [PATCH v7 0/5] Introduce provisioning primitives Sarthak Kukreti
2023-05-18 22:33 ` [PATCH v7 1/5] block: Don't invalidate pagecache for invalid falloc modes Sarthak Kukreti
2023-05-19  4:09   ` Christoph Hellwig
2023-05-19 15:17   ` Darrick J. Wong
2023-05-18 22:33 ` [PATCH v7 2/5] block: Introduce provisioning primitives Sarthak Kukreti
2023-05-19  4:18   ` Christoph Hellwig
2023-06-09 20:00   ` Mike Snitzer
2023-05-18 22:33 ` [PATCH v7 3/5] dm: Add block provisioning support Sarthak Kukreti
2023-05-18 22:33 ` [PATCH v7 4/5] dm-thin: Add REQ_OP_PROVISION support Sarthak Kukreti
2023-05-19 15:23   ` Mike Snitzer
2023-06-08 21:24     ` Mike Snitzer
2023-06-09  0:28       ` Mike Snitzer
2023-05-18 22:33 ` [PATCH v7 5/5] loop: Add support for provision requests Sarthak Kukreti
2023-05-22 16:37   ` [dm-devel] " Darrick J. Wong
2023-05-22 22:09     ` Sarthak Kukreti
2023-05-23  1:22       ` Darrick J. Wong
2023-10-07  1:29         ` Sarthak Kukreti
2023-05-19  4:09 ` [PATCH v7 0/5] Introduce provisioning primitives Christoph Hellwig
2023-05-19 14:41   ` Mike Snitzer
2023-05-19 23:07     ` Dave Chinner
2023-05-22 18:27       ` Mike Snitzer
2023-05-23 14:05         ` Brian Foster
2023-05-23 15:26           ` Mike Snitzer
2023-05-24  0:40             ` Dave Chinner
2023-05-24 20:02               ` Mike Snitzer
2023-05-25 11:39                 ` Dave Chinner
2023-05-25 16:00                   ` Mike Snitzer
2023-05-25 22:47                     ` Sarthak Kukreti
2023-05-26  1:36                       ` Dave Chinner
2023-05-26  2:35                         ` Sarthak Kukreti
2023-05-26 15:56                           ` Brian Foster
2023-05-25 16:19               ` Brian Foster
2023-05-26  9:37                 ` Dave Chinner
2023-05-26 15:47                   ` Brian Foster
     [not found]                   ` <CAJ0trDbspRaDKzTzTjFdPHdB9n0Q9unfu1cEk8giTWoNu3jP8g@mail.gmail.com>
2023-05-26 23:45                     ` Dave Chinner
     [not found]                       ` <CAJ0trDZJQwvAzngZLBJ1hB0XkQ1HRHQOdNQNTw9nK-U5i-0bLA@mail.gmail.com>
2023-05-30 14:02                         ` Mike Snitzer [this message]
     [not found]                           ` <CAJ0trDaUOevfiEpXasOESrLHTCcr=oz28ywJU+s+YOiuh7iWow@mail.gmail.com>
2023-05-30 15:28                             ` Mike Snitzer
2023-06-02 18:44                               ` Sarthak Kukreti
2023-06-02 21:50                                 ` Mike Snitzer
2023-06-03  0:52                                 ` Dave Chinner
2023-06-03 15:57                                   ` Mike Snitzer
2023-06-05 21:14                                     ` Sarthak Kukreti
2023-06-07  2:15                                       ` Dave Chinner
2023-06-07 23:27                                       ` Mike Snitzer
2023-06-09 20:31                                         ` Mike Snitzer
2023-06-09 21:54                                           ` Dave Chinner
2023-10-07  1:30                                           ` Sarthak Kukreti
2023-06-07  2:01                                     ` Dave Chinner
2023-06-07 23:50                                       ` Mike Snitzer
2023-06-09  3:32                                         ` Dave Chinner
2023-06-08  2:03                                   ` Martin K. Petersen
2023-06-09  0:10                                     ` Dave Chinner

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