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pnfs: fix pnfs lock inversion of i_lock and cl_lock

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The pnfs code was using throughout the lock order i_lock, cl_lock.
This conflicts with the nfs delegation code.  Rework the pnfs code
to avoid taking both locks simultaneously.

Currently the code takes the double lock to add/remove the layout to a
nfs_client list, while atomically checking that the list of lsegs is
empty.  To avoid this, we rely on existing serializations.  When a
layout is initialized with lseg count equal zero, LAYOUTGET's
openstateid serialization is in effect, making it safe to assume it
stays zero unless we change it.  And once a layout's lseg count drops
to zero, it is set as DESTROYED and so will stay at zero.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Fred Isaman
2011-02-03 18:28:52 +00:00
committed by Trond Myklebust
parent 9f52c2525e
commit f49f9baac8
2 changed files with 26 additions and 18 deletions
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2
fs/nfs/callback_proc.c
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@@ -188,10 +188,10 @@ static u32 initiate_bulk_draining(struct nfs_client *clp,
rv = NFS4ERR_DELAY;
list_del_init(&lo->plh_bulk_recall);
spin_unlock(&ino->i_lock);
pnfs_free_lseg_list(&free_me_list);
put_layout_hdr(lo);
iput(ino);
}
pnfs_free_lseg_list(&free_me_list);
return rv;
}