On 01/08/2014 07:12 PM, Goldwyn Rodrigues wrote: > Hi Srini, > > On 01/08/2014 07:29 PM, Srinivas Eeda wrote: >> Hi Goldwyn, >> >> On 01/08/2014 04:12 PM, Goldwyn Rodrigues wrote: >>> Hi, >>> >>> >From the comments in fs/ocfs2/inode.h:90 it seems, this was used in >>> legacy ocfs2 systems when a node received unlink votes. Since unlink >>> votes has been done away with and replaced with open locks, is this >>> flag still required? If yes, why? >> My understanding is that unlink voting protocol was heavy. So the >> following was done to address it. >> >> To do an unlink, dentry has to be removed. In order to do that the node >> has to get EX lock on the dentry which means all other nodes have to >> downconvert. In general EX lock on dentry is acquired only in unlink and >> I assume rename case. So all nodes which down convert the lock mark >> their inode OCFS2_INODE_MAYBE_ORPHANED. The only problem with this is >> that dentry on a node can get purged because of memory pressure which >> marks inode as OCFS2_INODE_MAYBE_ORPHANED even when no unlink was done >> on this inode. >> > > I think you are getting confused between dentry_lock (dentry_lockres) > and open lock (ip_open_lockres). AFAICS, dentry locks are used to > control the remote dentries. I was trying to answer why we need OCFS2_INODE_MAYBE_ORPHANED flag, I guess I wasn't clear. I'll make an other attempt :).
One way for node A to tell node B that an unlink had happened on node A is by sending an explicit message(something similar to what we had in old release). When node B received such communication it marked inode with OCFS2_INODE_MAYBE_ORPHANED flag if it still had the inode in use. The other way(current implementation) is to indirectly tell it by asking node B to purge dentry lockres. Once node B has been informed that dentry lock has to be released, it assumes inode might have been unlinked somewhere and marks the inode with OCFS2_INODE_MAYBE_ORPHANED flag. So, we need OCFS2_INODE_MAYBE_ORPHANED flag to tell node B that it should finish the second phase of unlink(remove the inode from file system) when it closes the file. > >> >>> >From my ongoing investigation of unlink() times, it seems this flag is >>> causing the delay with releasing the open locks while downconverting >>> dentry locks. The flag is set _everytime_ a dentry downconvert is >>> performed even if the file is not scheduled to be deleted. If not, we >>> can be smartly evict the inodes which are *not* to be deleted >>> (i_nlink>0) by not offloading to ocfs2_wq. This way open lock will >>> release faster speeding up unlink on the deleting node. >>> >>> >> Are you referring to the delay caused by ocfs2_drop_dentry_lock queueing >> dentry locks to dentry_lock_list ?. If that's the case, have you tried >> removing following patches which introduced that behavior ? I think that >> quota's deadlock bug might have to be addressed differently ? >> >> ea455f8ab68338ba69f5d3362b342c115bea8e13 > > Yes, that should make some difference. Let me try that. However, I was > suggesting we do not set the OCFS2_INODE_MAYBE_ORPHANED flag in > ocfs2_dentry_convert_worker as well, but I am not sure of the > consequences and that is the reason I asked why it is used. > >> eb90e46458b08bc7c1c96420ca0eb4263dc1d6e5 >> bb44bf820481e19381ec549118e4ee0b89d56191 > > I did not find these gits. Which tree are you referring to? Sorry, my bad. Those commit id's were from my local repo. I meant f7b1aa69be138ad9d7d3f31fa56f4c9407f56b6a and 5fd131893793567c361ae64cbeb28a2a753bbe35 > >> >> The above patches were leaving orphan files around which was causing a >> big problem to some applications that removes lot of files which inturn >> caused intermittent hangs >> > > _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel