Re: [PATCH 1/2] No MDS mount error fix

[Li Wang <liwang@ubuntukylin.com>]

Well, after double-checking the code, it seems the wait process will be 
unconditionally waked up if new MDS map received. Is there a situation 
that the client is pushed a new MDS map, but still no mds active. If so,
maybe worth a little bit optimization such as calling check_new_map() to 
avoid the client be uselessly waked up ...

On 2013/12/9 22:26, Li Wang wrote:
> Personally, I don't think there is issue for current implementation,
> either. If no ACTIVE mds, the mount process put to wait, until updated
> MDS map received and with active mds present indicated in the map, it
> will be waked up and go on the mount process, otherwise, EIO returned if
> timeout. If it is boring to hang for a long time, you can specify a
> shorter mount timeout.
>
> On 2013/12/8 2:59, Mikhail Campos Guadamuz wrote:
>> For http://tracker.ceph.com/issues/4386
>>
>> It determines situation, when a user is trying to mount CephFS
>> with no MDS present. Return ECOMM from
>> open_root_dentry which can be analyzed then by ceph.mount
>>
>> Signed-off-by: Mikhail Campos Guadamuz <plageat90@gmail.com>
>> ---
>>   fs/ceph/mdsmap.c            | 19 ++++++++++++++++---
>>   fs/ceph/super.c             | 10 +++++++++-
>>   include/linux/ceph/mdsmap.h |  1 +
>>   3 files changed, 26 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
>> index 132b64e..3a6ba8a 100644
>> --- a/fs/ceph/mdsmap.c
>> +++ b/fs/ceph/mdsmap.c
>> @@ -12,6 +12,20 @@
>>
>>   #include "super.h"
>>
>> +/*
>> + * count active mds's
>> + */
>> +int ceph_mdsmap_active_mds_count(struct ceph_mdsmap *m)
>> +{
>> +    int n = 0;
>> +    int i;
>> +
>> +    for(i = 0; i < m->m_max_mds; ++i)
>> +    if(m->m_info[i].state > 0)
>> +        ++n;
>> +
>> +    return  n;
>> +}
>>
>>   /*
>>    * choose a random mds that is "up" (i.e. has a state > 0), or -1.
>> @@ -26,9 +40,8 @@ int ceph_mdsmap_get_random_mds(struct ceph_mdsmap *m)
>>           return 0;
>>
>>       /* count */
>> -    for (i = 0; i < m->m_max_mds; i++)
>> -        if (m->m_info[i].state > 0)
>> -            n++;
>> +    n = ceph_mdsmap_active_mds_count(m);
>> +
>>       if (n == 0)
>>           return -1;
>>
>> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
>> index 6627b26..4d33d68 100644
>> --- a/fs/ceph/super.c
>> +++ b/fs/ceph/super.c
>> @@ -674,7 +674,15 @@ static struct dentry *open_root_dentry(struct
>> ceph_fs_client *fsc,
>>       struct ceph_mds_request *req = NULL;
>>       int err;
>>       struct dentry *root;
>> -
>> +
>> +    /* check for mds*/
>> +    if( 0 == ceph_mdsmap_active_mds_count(mdsc->mdsmap) )
>> +    {
>> +        pr_info("active mds not found, possible not exist\n");
>> +        root = ERR_PTR( -ECOMM );
>> +        return root;
>> +    }
>> +
>>       /* open dir */
>>       dout("open_root_inode opening '%s'\n", path);
>>       req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_GETATTR,
>> USE_ANY_MDS);
>> diff --git a/include/linux/ceph/mdsmap.h b/include/linux/ceph/mdsmap.h
>> index 87ed09f..4d7d502 100644
>> --- a/include/linux/ceph/mdsmap.h
>> +++ b/include/linux/ceph/mdsmap.h
>> @@ -56,6 +56,7 @@ static inline bool ceph_mdsmap_is_laggy(struct
>> ceph_mdsmap *m, int w)
>>       return false;
>>   }
>>
>> +extern int ceph_mdsmap_active_mds_count(struct ceph_mdsmap *m);
>>   extern int ceph_mdsmap_get_random_mds(struct ceph_mdsmap *m);
>>   extern struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end);
>>   extern void ceph_mdsmap_destroy(struct ceph_mdsmap *m);
>>