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Wed, 2 Jan 2019 08:57:47 +0000 (UTC) Subject: Re: [PATCH] btrfs-progs: Update backup roots when writing super blocks To: Qu Wenruo , linux-btrfs@vger.kernel.org References: <20181225052845.26322-1-wqu@suse.com> From: Nikolay Borisov Openpgp: preference=signencrypt Autocrypt: addr=nborisov@suse.com; prefer-encrypt=mutual; keydata= mQINBFiKBz4BEADNHZmqwhuN6EAzXj9SpPpH/nSSP8YgfwoOqwrP+JR4pIqRK0AWWeWCSwmZ T7g+RbfPFlmQp+EwFWOtABXlKC54zgSf+uulGwx5JAUFVUIRBmnHOYi/lUiE0yhpnb1KCA7f u/W+DkwGerXqhhe9TvQoGwgCKNfzFPZoM+gZrm+kWv03QLUCr210n4cwaCPJ0Nr9Z3c582xc bCUVbsjt7BN0CFa2BByulrx5xD9sDAYIqfLCcZetAqsTRGxM7LD0kh5WlKzOeAXj5r8DOrU2 GdZS33uKZI/kZJZVytSmZpswDsKhnGzRN1BANGP8sC+WD4eRXajOmNh2HL4P+meO1TlM3GLl EQd2shHFY0qjEo7wxKZI1RyZZ5AgJnSmehrPCyuIyVY210CbMaIKHUIsTqRgY5GaNME24w7h TyyVCy2qAM8fLJ4Vw5bycM/u5xfWm7gyTb9V1TkZ3o1MTrEsrcqFiRrBY94Rs0oQkZvunqia c+NprYSaOG1Cta14o94eMH271Kka/reEwSZkC7T+o9hZ4zi2CcLcY0DXj0qdId7vUKSJjEep c++s8ncFekh1MPhkOgNj8pk17OAESanmDwksmzh1j12lgA5lTFPrJeRNu6/isC2zyZhTwMWs k3LkcTa8ZXxh0RfWAqgx/ogKPk4ZxOXQEZetkEyTFghbRH2BIwARAQABtCNOaWtvbGF5IEJv cmlzb3YgPG5ib3Jpc292QHN1c2UuY29tPokCOAQTAQIAIgUCWIo48QIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQcb6CRuU/KFc0eg/9GLD3wTQz9iZHMFbjiqTCitD7B6dTLV1C ddZVlC8Hm/TophPts1bWZORAmYIihHHI1EIF19+bfIr46pvfTu0yFrJDLOADMDH+Ufzsfy2v HSqqWV/nOSWGXzh8bgg/ncLwrIdEwBQBN9SDS6aqsglagvwFD91UCg/TshLlRxD5BOnuzfzI Leyx2c6YmH7Oa1R4MX9Jo79SaKwdHt2yRN3SochVtxCyafDlZsE/efp21pMiaK1HoCOZTBp5 VzrIP85GATh18pN7YR9CuPxxN0V6IzT7IlhS4Jgj0NXh6vi1DlmKspr+FOevu4RVXqqcNTSS E2rycB2v6cttH21UUdu/0FtMBKh+rv8+yD49FxMYnTi1jwVzr208vDdRU2v7Ij/TxYt/v4O8 V+jNRKy5Fevca/1xroQBICXsNoFLr10X5IjmhAhqIH8Atpz/89ItS3+HWuE4BHB6RRLM0gy8 T7rN6ja+KegOGikp/VTwBlszhvfLhyoyjXI44Tf3oLSFM+8+qG3B7MNBHOt60CQlMkq0fGXd mm4xENl/SSeHsiomdveeq7cNGpHi6i6ntZK33XJLwvyf00PD7tip/GUj0Dic/ZUsoPSTF/mG EpuQiUZs8X2xjK/AS/l3wa4Kz2tlcOKSKpIpna7V1+CMNkNzaCOlbv7QwprAerKYywPCoOSC 7P25Ag0EWIoHPgEQAMiUqvRBZNvPvki34O/dcTodvLSyOmK/MMBDrzN8Cnk302XfnGlW/YAQ csMWISKKSpStc6tmD+2Y0z9WjyRqFr3EGfH1RXSv9Z1vmfPzU42jsdZn667UxrRcVQXUgoKg QYx055Q2FdUeaZSaivoIBD9WtJq/66UPXRRr4H/+Y5FaUZx+gWNGmBT6a0S/GQnHb9g3nonD jmDKGw+YO4P6aEMxyy3k9PstaoiyBXnzQASzdOi39BgWQuZfIQjN0aW+Dm8kOAfT5i/yk59h VV6v3NLHBjHVw9kHli3jwvsizIX9X2W8tb1SefaVxqvqO1132AO8V9CbE1DcVT8fzICvGi42 FoV/k0QOGwq+LmLf0t04Q0csEl+h69ZcqeBSQcIMm/Ir+NorfCr6HjrB6lW7giBkQl6hhomn l1mtDP6MTdbyYzEiBFcwQD4terc7S/8ELRRybWQHQp7sxQM/Lnuhs77MgY/e6c5AVWnMKd/z MKm4ru7A8+8gdHeydrRQSWDaVbfy3Hup0Ia76J9FaolnjB8YLUOJPdhI2vbvNCQ2ipxw3Y3c KhVIpGYqwdvFIiz0Fej7wnJICIrpJs/+XLQHyqcmERn3s/iWwBpeogrx2Lf8AGezqnv9woq7 OSoWlwXDJiUdaqPEB/HmGfqoRRN20jx+OOvuaBMPAPb+aKJyle8zABEBAAGJAh8EGAECAAkF AliKBz4CGwwACgkQcb6CRuU/KFdacg/+M3V3Ti9JYZEiIyVhqs+yHb6NMI1R0kkAmzsGQ1jU zSQUz9AVMR6T7v2fIETTT/f5Oout0+Hi9cY8uLpk8CWno9V9eR/B7Ifs2pAA8lh2nW43FFwp IDiSuDbH6oTLmiGCB206IvSuaQCp1fed8U6yuqGFcnf0ZpJm/sILG2ECdFK9RYnMIaeqlNQm iZicBY2lmlYFBEaMXHoy+K7nbOuizPWdUKoKHq+tmZ3iA+qL5s6Qlm4trH28/fPpFuOmgP8P K+7LpYLNSl1oQUr+WlqilPAuLcCo5Vdl7M7VFLMq4xxY/dY99aZx0ZJQYFx0w/6UkbDdFLzN upT7NIN68lZRucImffiWyN7CjH23X3Tni8bS9ubo7OON68NbPz1YIaYaHmnVQCjDyDXkQoKC R82Vf9mf5slj0Vlpf+/Wpsv/TH8X32ajva37oEQTkWNMsDxyw3aPSps6MaMafcN7k60y2Wk/ TCiLsRHFfMHFY6/lq/c0ZdOsGjgpIK0G0z6et9YU6MaPuKwNY4kBdjPNBwHreucrQVUdqRRm RcxmGC6ohvpqVGfhT48ZPZKZEWM+tZky0mO7bhZYxMXyVjBn4EoNTsXy1et9Y1dU3HVJ8fod 5UqrNrzIQFbdeM0/JqSLrtlTcXKJ7cYFa9ZM2AP7UIN9n1UWxq+OPY9YMOewVfYtL8M= Message-ID: Date: Wed, 2 Jan 2019 10:57:46 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181225052845.26322-1-wqu@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 25.12.18 г. 7:28 ч., Qu Wenruo wrote: > The code is mostly ported from kernel with minimal change. > > Since btrfs-progs doesn't support replaying log, there is some code > unnecessary for btrfs-progs, but to keep the code the same, that > unnecessary code is kept as it. > > Now "btrfs check --repair" will update backup roots correctly. > > Signed-off-by: Qu Wenruo > --- > disk-io.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 78 insertions(+) > > diff --git a/disk-io.c b/disk-io.c > index 133835a4d063..f28a6b526391 100644 > --- a/disk-io.c > +++ b/disk-io.c > @@ -1621,6 +1621,83 @@ write_err: > return ret; > } > > +/* > + * copy all the root pointers into the super backup array. > + * this will bump the backup pointer by one when it is > + * done > + */ > +static void backup_super_roots(struct btrfs_fs_info *info) > +{ > + struct btrfs_root_backup *root_backup; > + int next_backup; > + int last_backup; > + > + last_backup = find_best_backup_root(info->super_copy); Slightly offtopic: but find_best_backup_root only partially resembles it's kernel counterpart - find_newest_super_backup. And it's missing the code for handling wraparound. So in kernel space if the newest root is at index 3 and index 0 backup also has the same gen then we switch the index to 0, why is this needed? In any case I think 'find_best_backup_root' in progs should be renamed to 'find_newest_super_backup' and copied from kernel space. > + next_backup = (last_backup + 1) % BTRFS_NUM_BACKUP_ROOTS; This logic is different than the kernel one which does: last_backup = (next_backup + BTRFS_NUM_BACKUP_ROOTS - 1) % BTRFS_NUM_BACKUP_ROOTS; So in the kernel when info->backup_root_index == 0 then the newest backup root is going to be written at position 3, the next one in pos 1, the next in pos 2 and so on. OTOH in userspace we might potentially start writing at 1 (which doesn't seem problematic per se). So why the difference in logic? > + > + /* just overwrite the last backup if we're at the same generation */ > + root_backup = info->super_copy->super_roots + last_backup; > + if (btrfs_backup_tree_root_gen(root_backup) == > + btrfs_header_generation(info->tree_root->node)) > + next_backup = last_backup; > + > + root_backup = info->super_copy->super_roots + next_backup; > + > + /* > + * make sure all of our padding and empty slots get zero filled > + * regardless of which ones we use today > + */ > + memset(root_backup, 0, sizeof(*root_backup)); > + btrfs_set_backup_tree_root(root_backup, info->tree_root->node->start); > + btrfs_set_backup_tree_root_gen(root_backup, > + btrfs_header_generation(info->tree_root->node)); > + btrfs_set_backup_tree_root_level(root_backup, > + btrfs_header_level(info->tree_root->node)); > + > + btrfs_set_backup_chunk_root(root_backup, info->chunk_root->node->start); > + btrfs_set_backup_chunk_root_gen(root_backup, > + btrfs_header_generation(info->chunk_root->node)); > + btrfs_set_backup_chunk_root_level(root_backup, > + btrfs_header_level(info->chunk_root->node)); > + > + btrfs_set_backup_extent_root(root_backup, info->extent_root->node->start); > + btrfs_set_backup_extent_root_gen(root_backup, > + btrfs_header_generation(info->extent_root->node)); > + btrfs_set_backup_extent_root_level(root_backup, > + btrfs_header_level(info->extent_root->node)); > + /* > + * we might commit during log recovery, which happens before we set > + * the fs_root. Make sure it is valid before we fill it in. > + */ > + if (info->fs_root && info->fs_root->node) { > + btrfs_set_backup_fs_root(root_backup, > + info->fs_root->node->start); > + btrfs_set_backup_fs_root_gen(root_backup, > + btrfs_header_generation(info->fs_root->node)); > + btrfs_set_backup_fs_root_level(root_backup, > + btrfs_header_level(info->fs_root->node)); > + } > + > + btrfs_set_backup_dev_root(root_backup, info->dev_root->node->start); > + btrfs_set_backup_dev_root_gen(root_backup, > + btrfs_header_generation(info->dev_root->node)); > + btrfs_set_backup_dev_root_level(root_backup, > + btrfs_header_level(info->dev_root->node)); > + > + btrfs_set_backup_csum_root(root_backup, info->csum_root->node->start); > + btrfs_set_backup_csum_root_gen(root_backup, > + btrfs_header_generation(info->csum_root->node)); > + btrfs_set_backup_csum_root_level(root_backup, > + btrfs_header_level(info->csum_root->node)); > + > + btrfs_set_backup_total_bytes(root_backup, > + btrfs_super_total_bytes(info->super_copy)); > + btrfs_set_backup_bytes_used(root_backup, > + btrfs_super_bytes_used(info->super_copy)); > + btrfs_set_backup_num_devices(root_backup, > + btrfs_super_num_devices(info->super_copy)); > +}; > + > int write_all_supers(struct btrfs_fs_info *fs_info) > { > struct list_head *head = &fs_info->fs_devices->devices; > @@ -1630,6 +1707,7 @@ int write_all_supers(struct btrfs_fs_info *fs_info) > int ret; > u64 flags; > > + backup_super_roots(fs_info); > sb = fs_info->super_copy; > dev_item = &sb->dev_item; > list_for_each_entry(dev, head, dev_list) { >