ocfs2: fix slow deleting
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Cover letter [Ocfs2-devel] [PATCH 0/3] ocfs2: fix slow deleting
Below is excerpts from Joel's email for the same question :)
Quoted 4 lines
Currently, orphan scan just iterate all the slots and call
ocfs2_queue_recovery_completion, but I don't think it is proper for a node to query another mounted one since that node will query it by itself.
Node 1 has an inode it was using. The dentry went away due to
memory pressure. Node 1 closes the inode, but it's on the free list. The node has the open lock.
Node 2 unlinks the inode. It grabs the dentry lock to notify
others, but node 1 has no dentry and doesn't get the message. It trylocks the open lock, sees that another node has a PR, and does nothing.
Later node 2 runs its orphan dir. It igets the inode, trylocks
the open lock, sees the PR still, and does nothing.
Basically, we have to trigger an orphan iput on node 1. The
only way for this to happen is if node 1 runs node 2's orphan dir. This patch exists because that wasn't happening.
Quoted 24 lines · Sunil Mushran
Quoted 14 lines · Sunil Mushran
Quoted 6 lines · Srinivas Eeda
Quoted 5 lines · Sunil Mushran
2. All nodes have to scan all slots. Even live slots. I remember we did for
a reason. And that reason should be in the comment in the patch written
by Srini.Quoted 7 lines
When a node unlinks a file it inserts an entry into it's own orphan slot. If another node is the last one to close the file and dentry got flushed then it will not do the cleanup as it doesn't know the file was orphaned. The file will remain in the orphan slot till the node umounts
and the same slot is reused again. To overcome this problem a node has to rescan all slots(including live slots) and try to do the cleanup.Quoted 3 lines
The qs is not why are we scanning all live slots on all nodes. As in, why not just recover the local slot. There was a reason for that. Yes, we have to recover unused slots for the reason listed previously.
bleh.... let me rephrase.
The qs is why are we scanning all live slots on all nodes. Wengangs patch limits the scanning to the local (live) slot only. And I remember we had a reason for it.