Re: [PATCH 3/3] btrfs: Do super block verification before writing it to disk

Qu Wenruo
2018-04-19T10:32:46Z

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On 2018年04月19日 18:16, David Sterba wrote:
> Looks good, some minor comments below. I'm wondering how to test that.

Currently I'm using the most stupid way to test it, insert code randomly
modifies super blocks.

> We'd have to inject either the corruption or to provide a way to
> forcibly fail the test. For the latter a debugfs should do, I'll send
> something for comments.

What about a sysfs interface to modify super blocks?
Since we already have sectorsize and nodessize, allow it to be writeable
for CONFIG_BTRFS_DEBUG looks pretty good.

Thanks,
Qu

>
> On Thu, Apr 19, 2018 at 05:38:16PM +0800, Qu Wenruo wrote:
>> @@ -3563,6 +3565,12 @@ int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors)
>> sb = fs_info->super_for_commit;
>> dev_item = &sb->dev_item;
>>
>> + if (btrfs_check_super_valid(fs_info, sb, -1)) {
>
> A comment that this is skipping the bytenr check would be good.
>
>> + btrfs_err(fs_info,
>> + "superblock corruption detected before transaction commitment");
>
> commit
>
>
>> + return -EUCLEAN;
>> + }
>> +
>> mutex_lock(&fs_info->fs_devices->device_list_mutex);
>> head = &fs_info->fs_devices->devices;
>> max_errors = btrfs_super_num_devices(fs_info->super_copy) - 1;
>> @@ -3974,9 +3982,18 @@ int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid, int level,
>> level, first_key);
>> }
>>
>> -static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info)
>> +/*
>> + * Check the validation of btrfs super block.
>> + *
>> + * @sb: super block to check
>> + * @super_mirror: the super block number to check its bytenr.
>> + * 0 means the primary (1st) sb, 1 and 2 means 2nd and
>> + * 3rd backup sb, while -1 means to skip bytenr check.
>> + */
>> +static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
>> + struct btrfs_super_block *sb,
>> + int super_mirror)
>> {
>> - struct btrfs_super_block *sb = fs_info->super_copy;
>> u64 nodesize = btrfs_super_nodesize(sb);
>> u64 sectorsize = btrfs_super_sectorsize(sb);
>> int ret = 0;
>> @@ -4019,7 +4036,7 @@ static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info)
>> * Check sectorsize and nodesize first, other check will need it.
>> * Check all possible sectorsize(4K, 8K, 16K, 32K, 64K) here.
>> */
>> - if (!is_power_of_2(sectorsize) || sectorsize < 4096 ||
>> + if (!is_power_of_2(sectorsize) || sectorsize < SZ_4K ||
>
> No unrelated changes please. There are some remaining raw values, send a
> separate patch if you want to convert them.
>
>> sectorsize > BTRFS_MAX_METADATA_BLOCKSIZE) {
>> btrfs_err(fs_info, "invalid sectorsize %llu", sectorsize);
>> ret = -EINVAL;
>> @@ -4088,9 +4105,10 @@ static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info)
>> ret = -EINVAL;
>> }
>>
>> - if (btrfs_super_bytenr(sb) != BTRFS_SUPER_INFO_OFFSET) {
>> - btrfs_err(fs_info, "super offset mismatch %llu != %u",
>> - btrfs_super_bytenr(sb), BTRFS_SUPER_INFO_OFFSET);
>> + if (super_mirror >= 0 && btrfs_super_bytenr(sb) !=
>> + btrfs_sb_offset(super_mirror)) {
>> + btrfs_err(fs_info, "super offset mismatch %llu != %llu",
>> + btrfs_super_bytenr(sb), btrfs_sb_offset(super_mirror));
>> ret = -EINVAL;
>> }
>>
>> --
>> 2.17.0
>>
>> --
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