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

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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On 2018年04月16日 20:55, Anand Jain wrote:
> 
> 
> On 04/16/2018 10:02 AM, Qu Wenruo wrote:
>> There are already 2 reports about strangely corrupted super blocks,
>> where csum type and incompat flags get some obvious garbage, but csum
>> still matches and all other vitals are correct.
>>
>> This normally means some kernel memory corruption happens, although the
>> cause is unknown, at least detect it and prevent further corruption.
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
> 
>  Can you help point those 2 cases here?

Did you mean the reported-by tags?
If so, no problem.

Thanks,
Qu
> 
> Thanks, Anand
> 
> 
>>   fs/btrfs/disk-io.c | 24 ++++++++++++++++++++----
>>   1 file changed, 20 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
>> index 23803102aa0d..10d814f03f13 100644
>> --- a/fs/btrfs/disk-io.c
>> +++ b/fs/btrfs/disk-io.c
>> @@ -68,7 +68,8 @@
>>   static const struct extent_io_ops btree_extent_io_ops;
>>   static void end_workqueue_fn(struct btrfs_work *work);
>>   static void free_fs_root(struct btrfs_root *root);
>> -static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info);
>> +static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
>> +                   struct btrfs_super_block *sb);
>>   static void btrfs_destroy_ordered_extents(struct btrfs_root *root);
>>   static int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
>>                         struct btrfs_fs_info *fs_info);
>> @@ -2680,7 +2681,7 @@ int open_ctree(struct super_block *sb,
>>         memcpy(fs_info->fsid, fs_info->super_copy->fsid,
>> BTRFS_FSID_SIZE);
>>   -    ret = btrfs_check_super_valid(fs_info);
>> +    ret = btrfs_check_super_valid(fs_info, fs_info->super_copy);
>>       if (ret) {
>>           btrfs_err(fs_info, "superblock contains fatal errors");
>>           err = -EINVAL;
>> @@ -3575,6 +3576,21 @@ int write_all_supers(struct btrfs_fs_info
>> *fs_info, int max_mirrors)
>>       sb = fs_info->super_for_commit;
>>       dev_item = &sb->dev_item;
>>   +    /* Do extra check on the sb to be written */
>> +    ret = btrfs_check_super_valid(fs_info, sb);
>> +    if (ret) {
>> +        btrfs_err(fs_info, "fatal superblock corrupted detected");
>> +        return -EUCLEAN;
>> +    }
>> +    /*
>> +     * Unknown incompat flags can't be mounted, so newly developed flags
>> +     * means corruption
>> +     */
>> +    if (btrfs_super_incompat_flags(sb) & ~BTRFS_FEATURE_INCOMPAT_SUPP) {
>> +        btrfs_err(fs_info, "fatal superblock corrupted detected");
>> +        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;
>> @@ -3985,9 +4001,9 @@ 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)
>> +static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
>> +                   struct btrfs_super_block *sb)
>>   {
>> -    struct btrfs_super_block *sb = fs_info->super_copy;
>>       u64 nodesize = btrfs_super_nodesize(sb);
>>       u64 sectorsize = btrfs_super_sectorsize(sb);
>>       int ret = 0;
>>
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