From: Christoph Hellwig <hch@infradead.org>
To: Sergei Shtepa <sergei.shtepa@veeam.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Dave Chinner <david@fromorbit.com>,
axboe@kernel.dk, corbet@lwn.net, snitzer@kernel.org,
viro@zeniv.linux.org.uk, brauner@kernel.org, dchinner@redhat.com,
willy@infradead.org, dlemoal@kernel.org, linux@weissschuh.net,
jack@suse.cz, ming.lei@redhat.com, linux-block@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
Donald Buczek <buczek@molgen.mpg.de>
Subject: Re: [PATCH v5 04/11] blksnap: header file of the module interface
Date: Wed, 14 Jun 2023 07:07:16 -0700 [thread overview]
Message-ID: <ZInJlD70tMKoBi7T@infradead.org> (raw)
In-Reply-To: <733f591e-0e8f-8668-8298-ddb11a74df81@veeam.com>
On Wed, Jun 14, 2023 at 11:26:20AM +0200, Sergei Shtepa wrote:
> This code worked quite successfully for the veeamsnap module, on the
> basis of which blksnap was created. Indeed, such an allocation of an
> area on a block device using a file does not look safe.
>
> We've already discussed this with Donald Buczek <buczek@molgen.mpg.de>.
> Link: https://github.com/veeam/blksnap/issues/57#issuecomment-1576569075
> And I have planned work on moving to a more secure ioctl in the future.
> Link: https://github.com/veeam/blksnap/issues/61
>
> Now, thanks to Dave, it becomes clear to me how to solve this problem best.
> swapfile is a good example of how to do it right.
I don't actually think swapfile is a very good idea, in fact the Linux
swap code in general is not a very good place to look for inspirations
:)
IFF the usage is always to have a whole file for the diff storage the
over all API is very simple - just pass a fd to the kernel for the area,
and then use in-kernel direct I/O on it. Now if that file should also
be able to reside on the same file system that the snapshot is taken
of things get a little more complicated, because writes to it also need
to automatically set the BIO_REFFED flag. I have some ideas for that
and will share some draft code with you.
next prev parent reply other threads:[~2023-06-14 14:07 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-12 13:52 [PATCH v5 00/11] blksnap - block devices snapshots module Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 01/11] documentation: Block Device Filtering Mechanism Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 02/11] block: " Sergei Shtepa
2023-07-11 2:02 ` Yu Kuai
2023-07-12 10:04 ` Yu Kuai
2023-07-12 12:34 ` Yu Kuai
2023-07-17 17:39 ` Sergei Shtepa
2023-07-18 1:21 ` Yu Kuai
2023-07-17 16:22 ` Sergei Shtepa
2023-07-17 14:39 ` Sergei Shtepa
2023-07-18 1:37 ` Yu Kuai
2023-07-18 11:25 ` Sergei Shtepa
2023-07-18 12:32 ` Yu Kuai
2023-07-18 16:33 ` Sergei Shtepa
2023-07-19 7:28 ` Yu Kuai
2023-07-19 8:36 ` Sergei Shtepa
2023-07-20 6:14 ` Christoph Hellwig
2023-06-12 13:52 ` [PATCH v5 03/11] documentation: Block Devices Snapshots Module Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 04/11] blksnap: header file of the module interface Sergei Shtepa
2023-06-13 22:25 ` Dave Chinner
2023-06-14 6:26 ` Christoph Hellwig
2023-06-14 9:26 ` Sergei Shtepa
2023-06-14 14:07 ` Christoph Hellwig [this message]
2023-06-14 16:43 ` Sergei Shtepa
2023-06-15 0:08 ` Dave Chinner
2023-07-17 18:57 ` Thomas Weißschuh
2023-07-18 9:53 ` Sergei Shtepa
2023-07-20 6:16 ` Christoph Hellwig
2023-06-12 13:52 ` [PATCH v5 05/11] blksnap: module management interface functions Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 06/11] blksnap: handling and tracking I/O units Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 07/11] blksnap: minimum data storage unit of the original block device Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 08/11] blksnap: difference storage Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 09/11] blksnap: event queue from the " Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 10/11] blksnap: snapshot and snapshot image block device Sergei Shtepa
2023-06-12 13:52 ` [PATCH v5 11/11] blksnap: Kconfig and Makefile Sergei Shtepa
2023-06-12 14:32 ` [PATCH v5 00/11] blksnap - block devices snapshots module Christoph Hellwig
2023-06-12 16:19 ` Eric Biggers
2023-06-13 5:50 ` Christoph Hellwig
2023-06-13 10:12 ` Sergei Shtepa
2023-06-14 17:22 ` Eric Biggers
-- strict thread matches above, loose matches on Subject: below --
2023-06-12 13:21 Sergei Shtepa
2023-06-12 13:21 ` [PATCH v5 04/11] blksnap: header file of the module interface Sergei Shtepa
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