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[91.66.68.233]) by smtp.googlemail.com with ESMTPSA id x38sm12123416edx.24.2019.01.25.08.59.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 08:59:58 -0800 (PST) Subject: Re: Retrieving CSUM-Tree To: Qu Wenruo , "linux-btrfs@vger.kernel.org" References: <4472aad4-86cb-7ce2-6055-1ff8d6955969@gmail.com> From: Tobias Reinhard Message-ID: <91b98362-9019-3199-990d-072466b1b455@gmail.com> Date: Fri, 25 Jan 2019 17:59:55 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-GB Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Am 13.01.2019 um 12:02 schrieb Qu Wenruo: > > 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 Sorry for my late response. If I set min_objectid = max_objectid = BTRFS_EXTENT_CSUM_OBJECTID I don't get anything. I have to set it to max=-1 (min doesn't matter). And in that I case, min_offset and max_offset doesn't matter - I always get the same result. I can even use "wrong" filters like min=1000 max=500. Tobias