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pNFS: Don't forget the layout stateid if there are outstanding LAYOUTGETs 

If there are outstanding LAYOUTGET rpc calls, then we want to ensure that
we keep the layout stateid around so we that don't inadvertently pick up
an old/misordered sequence id.
The race is as follows:

Client				Server
======				======
LAYOUTGET(seqid)
LAYOUTGET(seqid)
				return LAYOUTGET(seqid+1)
				return LAYOUTGET(seqid+2)
process LAYOUTGET(seqid+2)
	forget layout
process LAYOUTGET(seqid+1)

If it forgets the layout stateid before processing seqid+1, then
the client will not check the layout->plh_barrier, and so will set
the stateid with seqid+1.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Trond Myklebust 2016-09-04 12:46:35 -04:00
parent 52ec7be2e2
commit 334a8f3711
1 changed files with 2 additions and 1 deletions
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3
fs/nfs/pnfs.c
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@ -365,7 +365,8 @@ pnfs_layout_remove_lseg(struct pnfs_layout_hdr *lo,
/* Matched by pnfs_get_layout_hdr in pnfs_layout_insert_lseg */
atomic_dec(&lo->plh_refcount);
if (list_empty(&lo->plh_segs)) {
set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
if (atomic_read(&lo->plh_outstanding) == 0)
set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
clear_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags);
}
rpc_wake_up(&NFS_SERVER(inode)->roc_rpcwaitq);