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

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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);