[Cluster-devel] [PATCH 4 of 5] Bz #248176: GFS2: invalid metadata block - REVISED

[Wendy Cheng]

Sorry ... hand and head do not coordinate well. Somehow I use "spin 
lock" but it is actually a semaphore.... Wendy
> Bob Peterson wrote:
>> Part of the problem was that inodes were being recycled
>> before their buffers were flushed to the journal logs.
>>
>>   
> Set aside "after this patch, the problem goes away" thing ...
>
> I haven't checked previous three patches yet so I may not have the 
> overall picture ... but why adding the journal flush spin lock here 
> could prevent the new inode to get re-used before its associated 
> buffer are flushed to the logs ? Could you elaborate more ?
>
>> diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
>> index b93ac45..2d7f7ea 100644
>> --- a/fs/gfs2/rgrp.c
>> +++ b/fs/gfs2/rgrp.c
>> @@ -865,12 +865,15 @@ static struct inode *try_rgrp_unlink(struct 
>> gfs2_rgrpd *rgd, u64 *last_unlinked)
>>      struct inode *inode;
>>      u32 goal = 0, block;
>>      u64 no_addr;
>> +    struct gfs2_sbd *sdp = rgd->rd_sbd;
>>  
>>      for(;;) {
>>          if (goal >= rgd->rd_data)
>>              break;
>> +        down_write(&sdp->sd_log_flush_lock);
>>          block = rgblk_search(rgd, goal, GFS2_BLKST_UNLINKED,
>>                       GFS2_BLKST_UNLINKED);
>> +        up_write(&sdp->sd_log_flush_lock);
>>          if (block == BFITNOENT)
>>              break;
>>         
> My concern is that GFS2's usage of sd_log_flush_lock has been very 
> abused lately. The journal logic is gradually becoming difficult to 
> understand and maintain. With this change, we move a local spin lock 
> (that belongs to log.c) into another sub-component (rgrp). 
> Intuitively, this is not right.
>
> -- Wendy
>
>