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From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Max Reitz <mreitz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [PATCH v2 00/20] block/export: Allow exporting BDSs via FUSE
Date: Tue, 22 Sep 2020 16:58:38 +0100	[thread overview]
Message-ID: <20200922155838.GR1989025@redhat.com> (raw)
In-Reply-To: <20200922104932.46384-1-mreitz@redhat.com>

On Tue, Sep 22, 2020 at 12:49:12PM +0200, Max Reitz wrote:
> Based-on: <20200907182011.521007-1-kwolf@redhat.com>
>           (“block/export: Add infrastructure and QAPI for block exports”)
> 
> (Though its patch 16 needs a s/= \&blk_exp_nbd/= drv/ on top.)
> 
> v1: https://lists.nongnu.org/archive/html/qemu-block/2019-12/msg00451.html
> 
> Branch: https://github.com/XanClic/qemu.git fuse-exports-v2
> Branch: https://git.xanclic.moe/XanClic/qemu.git fuse-exports-v2
> 
> 
> Hi,
> 
> Ever since I found out that you can mount FUSE filesystems on regular
> files (not just directories), I had the idea of adding FUSE block
> exports to qemu where you can export block nodes as raw images.  The
> best thing is that you’d be able to mount an image on itself, so
> whatever format it may be in, qemu lets it appear as a raw image (and
> you can then use regular tools like dd on it).
> 
> The performance is quite bad so far, but we can always try to improve it
> if the need arises.  For now I consider it mostly a cute feature to get
> easy access to the raw contents of image files in any format (without
> requiring root rights).

Aside from the iotests, so you forsee any particular use cases
where this feature is desirable / important ?

Looking at it from a security POV, I'm not thrilled about the
idea of granting QEMU permission to use the mount syscall for
seccomp or SELinux. IOW, I expect this feature won't be something
we want to expose in QEMU guests managed by libvirt, which would
limit how widely it can be used.

QEMU can export NBD. Would it make sense to do this as an NBD
client ? There's already https://libguestfs.org/nbdfuse.1.html
but IIUC that exposes it as a file within a dir. Presumably
it is not too hard to make it support exposing it directly as
a file too.

I wonder how performance compares between your native FUSE
impl in QEMU vs NBD FUSE ?


Regards,
Daniel
-- 
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  parent reply	other threads:[~2020-09-22 16:02 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-22 10:49 [PATCH v2 00/20] block/export: Allow exporting BDSs via FUSE Max Reitz
2020-09-22 10:49 ` [PATCH v2 01/20] configure: Detect libfuse Max Reitz
2020-09-22 11:14   ` Thomas Huth
2020-09-22 11:21     ` Paolo Bonzini
2020-09-22 11:46     ` Max Reitz
2020-09-22 15:37     ` Max Reitz
2020-09-22 15:45       ` Paolo Bonzini
2020-09-22 10:49 ` [PATCH v2 02/20] fuse: Allow exporting BDSs via FUSE Max Reitz
2020-10-15  8:57   ` Kevin Wolf
2020-10-15 14:46     ` Max Reitz
2020-10-15 15:41       ` Kevin Wolf
2020-10-15 15:59         ` Max Reitz
2020-10-15 17:01           ` Kevin Wolf
2020-09-22 10:49 ` [PATCH v2 03/20] fuse: Implement standard FUSE operations Max Reitz
2020-10-15  9:46   ` Kevin Wolf
2020-10-15 15:18     ` Max Reitz
2020-10-15 15:58       ` Kevin Wolf
2020-10-15 16:04         ` Max Reitz
2020-09-22 10:49 ` [PATCH v2 04/20] fuse: Allow growable exports Max Reitz
2020-10-15 10:41   ` Kevin Wolf
2020-10-15 15:20     ` Max Reitz
2020-09-22 10:49 ` [PATCH v2 05/20] fuse: (Partially) implement fallocate() Max Reitz
2020-09-22 10:49 ` [PATCH v2 06/20] fuse: Implement hole detection through lseek Max Reitz
2020-09-22 10:49 ` [PATCH v2 07/20] iotests: Do not needlessly filter _make_test_img Max Reitz
2020-09-22 10:49 ` [PATCH v2 08/20] iotests: Do not pipe _make_test_img Max Reitz
2020-09-22 10:49 ` [PATCH v2 09/20] iotests: Use convert -n in some cases Max Reitz
2020-09-22 10:49 ` [PATCH v2 10/20] iotests/046: Avoid renaming images Max Reitz
2020-09-22 10:49 ` [PATCH v2 11/20] iotests: Derive image names from $TEST_IMG Max Reitz
2020-09-22 10:49 ` [PATCH v2 12/20] iotests/091: Use _cleanup_qemu instad of "wait" Max Reitz
2020-09-22 10:49 ` [PATCH v2 13/20] iotests: Restrict some Python tests to file Max Reitz
2020-09-22 10:49 ` [PATCH v2 14/20] iotests: Let _make_test_img guess $TEST_IMG_FILE Max Reitz
2020-09-22 10:49 ` [PATCH v2 15/20] iotests/287: Clean up subshell test image Max Reitz
2020-09-22 10:49 ` [PATCH v2 16/20] storage-daemon: Call bdrv_close_all() on exit Max Reitz
2020-09-22 10:49 ` [PATCH v2 17/20] iotests: Give access to the qemu-storage-daemon Max Reitz
2020-10-15 11:27   ` Kevin Wolf
2020-10-15 15:22     ` Max Reitz
2020-09-22 10:49 ` [PATCH v2 18/20] iotests: Allow testing FUSE exports Max Reitz
2020-10-15 11:43   ` Kevin Wolf
2020-10-15 15:27     ` Max Reitz
2020-09-22 10:49 ` [PATCH v2 19/20] iotests: Enable fuse for many tests Max Reitz
2020-09-22 10:49 ` [PATCH v2 20/20] iotests/308: Add test for FUSE exports Max Reitz
2020-09-22 15:58 ` Daniel P. Berrangé [this message]
2020-09-23  7:21   ` [PATCH v2 00/20] block/export: Allow exporting BDSs via FUSE Max Reitz
2020-09-23  9:08   ` Stefan Hajnoczi
2020-10-15 12:01 ` Kevin Wolf
2020-10-15 16:47   ` Max Reitz

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