From: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
To: <dsterba@suse.cz>, <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH] Btrfs-progs: fsck: add an option to check data csums
Date: Wed, 28 May 2014 09:34:53 +0800 [thread overview]
Message-ID: <53853D3D.8020105@cn.fujitsu.com> (raw)
In-Reply-To: <20140516154045.GZ6917@twin.jikos.cz>
On 05/16/2014 11:40 PM, David Sterba wrote:
> On Thu, May 08, 2014 at 09:26:49AM +0800, Wang Shilong wrote:
>> This patch adds an option '--check-data-csum' to verify data csums.
>> fsck won't check data csums unless users specify this option explictly.
> Nice.
>
>> +static int read_extent_data(struct btrfs_root *root, char *data,
>> + u64 logical, u64 len, int mirror)
>> +{
>> + if (read_len > root->sectorsize)
>> + read_len = root->sectorsize;
>> + if (read_len > bytes_left)
>> + read_len = bytes_left;
>> +
>> + ret = pread64(device->fd, data + offset, read_len,
>> + multi->stripes[0].physical);
> You can od kfree(multi) here and make the error/exit block simpler.
>
> kfree(multi);
> multi = NULL;
>
>> + if (ret != read_len)
> ret = -EIO;
>
>> + goto error;
>> + offset += read_len;
>> + bytes_left -= read_len;
>> + kfree(multi);
>> + multi = NULL;
>> + }
>> + return 0;
> return ret;
>
> Remove the rest.
>
>> +error:
>> + kfree(multi);
>> + return -EIO;
>> +}
>> +
>> +static int check_extent_csums(struct btrfs_root *root, u64 bytenr,
>> + u64 num_bytes, unsigned long leaf_offset,
>> + struct extent_buffer *eb) {
>> +
>> + u64 offset = 0;
>> + u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
>> + char *data;
>> + u32 crc;
>> + unsigned long tmp;
>> + char result[csum_size];
>> + char out[csum_size];
> A local variable of dynamic size, though we know it will not be larger
> than BTRFS_CSUM_SIZE. Please use that.
>
> csum_size should be validated during superblock read, so we can assume
> it's correct at this point.
>
>> + int ret = 0;
>> + __s64 cmp;
> This is used as a return value of memcmp, but both kernel and userspace
> libraries use simple int which is IMO enough.
>
>> + int mirror;
>> + int num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
>> + bytenr, num_bytes);
>> +
>> + BUG_ON(num_bytes % root->sectorsize);
> Can you do this check in the caller and avoid a BUG_ON here?
>
>> + data = malloc(root->sectorsize);
>> + if (!data)
>> + return -ENOMEM;
>> +
>> + while (offset < num_bytes) {
>> + mirror = 0;
>> +again:
>> + ret = read_extent_data(root, data, bytenr + offset,
>> + root->sectorsize, mirror);
>> + if (ret)
>> + goto out;
>> +
>> + crc = ~(u32)0;
>> + crc = btrfs_csum_data(NULL, (char *)data, crc,
>> + root->sectorsize);
>> + btrfs_csum_final(crc, result);
>> +
>> + tmp = leaf_offset + offset / root->sectorsize * csum_size;
>> + read_extent_buffer(eb, out, tmp, csum_size);
>> + cmp = memcmp(out, result, csum_size);
>> + if (cmp) {
>> + fprintf(stderr, "mirror: %d range bytenr: %llu, len: %d checksum mismatch\n",
>> + mirror, bytenr + offset, root->sectorsize);
> It has proved useful to print the checksums here, please enhance the
> output.
>
>> + if (mirror < num_copies - 1) {
>> + mirror += 1;
> mirror++;
>
>> + goto again;
>> + }
>> + }
>> + offset += root->sectorsize;
>> + }
>> +out:
>> + free(data);
>> + return ret;
>> +}
>> +
>> static int check_extent_exists(struct btrfs_root *root, u64 bytenr,
>> u64 num_bytes)
>> {
>> @@ -6678,6 +6790,7 @@ const char * const cmd_check_usage[] = {
>> "--repair try to repair the filesystem",
>> "--init-csum-tree create a new CRC tree",
>> "--init-extent-tree create a new extent tree",
>> + "--check-data-csum check data csums",
> The help text is not very useful, just repeats the option name without
> the dashes. Something like "verify checkums of data blocks" looks more
> readable to me.
Sorry for late reply, i will address your comments, and send a v2 later.
> .
>
prev parent reply other threads:[~2014-05-28 1:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-08 1:26 [PATCH] Btrfs-progs: fsck: add an option to check data csums Wang Shilong
2014-05-08 10:48 ` Konstantinos Skarlatos
2014-05-16 15:49 ` David Sterba
2014-05-16 15:40 ` David Sterba
2014-05-28 1:34 ` Wang Shilong [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=53853D3D.8020105@cn.fujitsu.com \
--to=wangsl.fnst@cn.fujitsu.com \
--cc=dsterba@suse.cz \
--cc=linux-btrfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).