Re: [PATCH] ndctl/dimm: Fix to dump namespace indexs and labels

["Liu, Jingqi" <jingqi.liu@intel.com>]

Hi Vishal,

Thanks for your comments.

On 7/8/2021 8:21 AM, Verma, Vishal L wrote:
> On Wed, 2021-06-09 at 11:06 +0800, Jingqi Liu wrote:
>> The following bug is caused by setting the size of Label Index Block
>> to a fixed 256 bytes.
>>
>> Use the following Qemu command to start a Guest with 2MB label-size:
>>        -object memory-backend-file,id=mem1,share=on,mem-path=/dev/dax1.1,size=14G,align=2M
>>        -device nvdimm,memdev=mem1,id=nv1,label-size=2M
>>
>> There is a namespace in the Guest as follows:
>>        $ ndctl list
>>        [
>>          {
>>            "dev":"namespace0.0",
>>            "mode":"devdax",
>>            "map":"dev",
>>            "size":14780727296,
>>            "uuid":"58ad5282-5a16-404f-b8ee-e28b4c784eb8",
>>            "chardev":"dax0.0",
>>            "align":2097152,
>>            "name":"namespace0.0"
>>          }
>>        ]
>>
>> Fail to read labels. The result is as follows:
>>        $ ndctl read-labels -u nmem0
>>        [
>>        ]
>>        read 0 nmem
>>
>> If using the following Qemu command to start the Guest with 128K
>> label-size, this label can be read correctly.
>>        -object memory-backend-file,id=mem1,share=on,mem-path=/dev/dax1.1,size=14G,align=2M
>>        -device nvdimm,memdev=mem1,id=nv1,label-size=128K
>>
>> The size of a Label Index Block depends on how many label slots fit into
>> the label storage area. The minimum size of an index block is 256 bytes
>> and the size must be a multiple of 256 bytes. For a storage area of 128KB,
>> the corresponding Label Index Block size is 256 bytes. But if the label
>> storage area is not 128KB, the Label Index Block size should not be 256 bytes.
>>
>> Namespace Label Index Block appears twice at the top of the label storage area.
>> Following the two index blocks, an array for storing labels takes up the
>> remainder of the label storage area.
>>
>> For obtaining the size of Namespace Index Block, we also cannot rely on
>> the field of 'mysize' in this index block since it might be corrupted.
>> Similar to the linux kernel, we use sizeof_namespace_index() to get the size
>> of Namespace Index Block. Then we can also correctly calculate the starting
>> offset of the following namespace labels.
>>
>> Suggested-by: Dan Williams <dan.j.williams@intel.com>
>> Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
>> ---
>>   ndctl/dimm.c           | 19 +++++++++++++++----
>>   ndctl/lib/dimm.c       |  5 +++++
>>   ndctl/lib/libndctl.sym |  1 +
>>   ndctl/libndctl.h       |  1 +
>>   4 files changed, 22 insertions(+), 4 deletions(-)
> 
> Hi Jingqi,
> 
> This looks fine, one comment below.
> 
> [..]
>>
>> diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
>> index 0a82616..0ce2bb9 100644
>> --- a/ndctl/lib/libndctl.sym
>> +++ b/ndctl/lib/libndctl.sym
>> @@ -290,6 +290,7 @@ global:
>>        ndctl_dimm_validate_labels;
>>        ndctl_dimm_init_labels;
>>        ndctl_dimm_sizeof_namespace_label;
>> +     ndctl_dimm_sizeof_namespace_index;
> 
> This can't go into an 'old' section of the symbol version script - if
> you base off the current 'pending' branch, you should see a LIBNDCTL_26
> section at the bottom. You can add this there.

It's based on the current 'master' branch.
I don't see a LIBNDCTL_26 section, just 'LIBNDCTL_25'.
How about adding 'ndctl_dimm_sizeof_namespace_index' to LIBNDCTL_25 
section ?

Thanks,
Jingqi