From: Qu Wenruo <quwenruo.btrfs@gmx.com>
To: Tobias Reinhard <trtracer@gmail.com>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: Retrieving
Date: Sun, 13 Jan 2019 19:02:38 +0800 [thread overview]
Message-ID: <a0e58490-8610-2b86-751f-772625fdf0ca@gmx.com> (raw)
In-Reply-To: <4472aad4-86cb-7ce2-6055-1ff8d6955969@gmail.com>
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On 2019/1/13 下午6:19, Tobias Reinhard wrote:
> Hi,
>
> I want to read the complete CSUM-Tree from userspace. I tried it via the
> ioctl. This is what the code looks like:
>
> struct btrfs_sv2_args sv2_args;
> int fd = open(filename, O_RDONLY);
> sv2_args.key.tree_id = BTRFS_CSUM_TREE_OBJECTID;
> sv2_args.key.min_objectid = 0;
> sv2_args.key.max_objectid = -1;
> sv2_args.key.min_offset = 0;
> sv2_args.key.max_offset = -1;
> sv2_args.key.min_transid = 0;
> sv2_args.key.max_transid = -1;
> sv2_args.key.min_type = BTRFS_CSUM_ITEM_KEY;
> sv2_args.key.max_type = BTRFS_CSUM_ITEM_KEY;
> sv2_args.key.nr_items = -1;
> sv2_args.buf_size = sizeof(sv2_args.buf);
> ioctl(fd, BTRFS_IOC_TREE_SEARCH_V2, &sv2_args);
>
> But the device is not small and I hit the limit of the
> btrfs_sv2_args.buf which seems to be 16 MB.
>
> How can I get the *complete* CSUM-Tree?
>
> Limiting to offset does not work (My first idea was to do it this way
> and get it in chunks).
That's strange.
Are you still using 0~-1 objectid and 0~-1 type, just last_offset~-1?
Have tried searching using the following parameters?
min_objectid = max_objectid = BTRFS_EXTENT_CSUM_OBJECTID
min_type = max_type = BTRFS_CSUM_ITEM_KEY;
min_offset = last_found_csum_offset
max_offset = -1
Thanks,
Qu
>
> Limiting to a single transid does not work as well because even one
> transid is larger than the limit.
>
> Kernel is 4.15.
>
> Any help would be appreciated.
>
> Best Regards
>
> Tobias
>
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next prev parent reply other threads:[~2019-01-13 11:02 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-13 10:19 Retrieving Tobias Reinhard
2019-01-13 11:02 ` Qu Wenruo [this message]
2019-01-25 16:59 ` Retrieving CSUM-Tree Tobias Reinhard
2019-01-25 18:05 ` Hans van Kranenburg
2019-01-25 20:45 ` Tobias Reinhard
2019-01-25 20:49 ` Hans van Kranenburg
2019-01-25 21:22 ` Retrieving Zygo Blaxell
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