[Ocfs2-tools-devel] [PATCH] o2image: return error if pread64 failed in ocfs2_image_load_bitmap()

[piaojun]

Hi Joseph,

On 2016-12-23 17:38, Joseph Qi wrote:
> Hi Jun,
> 
> 
> On 16/12/21 17:33, piaojun wrote:
>> In ocfs2_image_load_bitmap(), if pread64 failed, we need catch the
>> errno and return errno to upper callers. otherwise we may get the
>> incorrect 'arr_map' but 'o2image -I' execute successfully.
>>
>> Signed-off-by: Jun Piao <piaojun at huawei.com>
>> ---
>>   libocfs2/image.c | 15 ++++++++++-----
>>   1 file changed, 10 insertions(+), 5 deletions(-)
>>
>> diff --git a/libocfs2/image.c b/libocfs2/image.c
>> index fe95530..460616d 100644
>> --- a/libocfs2/image.c
>> +++ b/libocfs2/image.c
>> @@ -163,7 +163,7 @@ errcode_t ocfs2_image_load_bitmap(ocfs2_filesys *ofs)
>>       struct ocfs2_image_state *ost;
>>       struct ocfs2_image_hdr *hdr;
>>       uint64_t blk_off, bits_set;
>> -    int count, i, j, fd;
>> +    int count = 0, tmp, i, j, fd;
>>       errcode_t ret;
>>       char *blk;
>>   @@ -216,10 +216,15 @@ errcode_t ocfs2_image_load_bitmap(ocfs2_filesys *ofs)
>>            * we don't use io_read_block as ocfs2 image bitmap block size
>>            * could be different from filesystem block size
>>            */
>> -        count = pread64(fd, ost->ost_bmparr[i].arr_map,
>> -                ost->ost_bmpblksz, blk_off);
>> -        if (count < ost->ost_bmpblksz)
>> -            goto out;
>> +        while (count < ost->ost_bmpblksz) {
>> +            tmp = pread64(fd, ost->ost_bmparr[i].arr_map + count,
>> +                ost->ost_bmpblksz - count, blk_off + count);
>> +            if (tmp <= 0) {
>> +                ret = OCFS2_ET_IO;
>> +                goto out;
>> +            }
>> +            count += tmp;
>> +        }
> In which case we need loop read?
> Or shall we just set the error code if read fails?
> 
> Thanks,
> Joseph
The usage of pread64 refers to unix_io_read_block() in unix_io.c.
I have not catch the case we need loop read but I think it is safer by
loop reading in case of incomplete data.

Thanks,
Jun
>>             /* add bits set in this bitmap */
>>           for (j = 0; j < (ost->ost_bmpblksz * 8); j++)
> 
> 
>