This fix will cause problems for regular file unlinks. If the inode is
not cleared on node 2, then both node 1 and node 2 will fail to get try
open lock and fail to clear the orphan inodes.
I am assuming the deadlock you have seen is because of quota's enabled
and fix e3a767b60fd8a9f5e133f42f4970cff77ec43173 should have avoided
this deadlock by delaying the dropping of the dquot reference. That
didn't happen ? Why else is downconvert task taking the inode lock ?
Thanks,
--Srini
On 10/19/2014 10:28 PM, Wengang Wang wrote:
> There is dead lock case like this(the Dentry is a dentry to the Inode):
>
> node 1 node 2
> ------------------- --------------------------
>
> granted inode lock
>
> requesting dentry lock
> responding to node 1 request on dentry lock,
> it calls ocfs2_do_drop_dentry_lock with the
> call trace:
> #4 wait_for_completion
> #5 __ocfs2_cluster_lock
> #6 ocfs2_inode_lock_full_nested
> #7 ocfs2_evict_inode
> #8 evict
> #9 iput
> #10 ocfs2_do_drop_dentry_lock
>
> You can see node 2 is requesting the inode lock before unlocking dentry lock
> thus a two nodes dead lock formed.
>
> The story is like this:
>
> Responding node 1's request, Node 2, ocfs2_dentry_convert_worker, returned
> UNBLOCK_STOP_POST which means don't downconvert but do post_unlock action.
> It was doing so because it thought it doesn't need to downconvert but will do
> an unlock instead in the post_unlock action ocfs2_dentry_post_unlock().
> By doing so it can save a clusted downconvert request for performace
> consideration. But in ocfs2_dentry_post_unlock() before unlock the dentry
> lock,
> it was requesting the inode lock forming the deadlock expectedly.
>
> Fix:
> unlock dentry lock first before the requesting inode lock in
> ocfs2_do_drop_dentry_lock.
>
> Signed-off-by: Wengang Wang <wen.gang.w...@oracle.com>
> ---
> fs/ocfs2/dcache.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ocfs2/dcache.c b/fs/ocfs2/dcache.c
> index e2e05a1..19a7d6c 100644
> --- a/fs/ocfs2/dcache.c
> +++ b/fs/ocfs2/dcache.c
> @@ -369,9 +369,9 @@ out_attach:
> static void ocfs2_drop_dentry_lock(struct ocfs2_super *osb,
> struct ocfs2_dentry_lock *dl)
> {
> - iput(dl->dl_inode);
> ocfs2_simple_drop_lockres(osb, &dl->dl_lockres);
> ocfs2_lock_res_free(&dl->dl_lockres);
> + iput(dl->dl_inode);
> kfree(dl);
> }
>
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