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NFSv4/pNFS: Fix a layoutget livelock loop 

If NFS_LAYOUT_RETURN_REQUESTED is set, but there is no value set for
the layout plh_return_seq, we can end up in a livelock loop in which
every layout segment retrieved by a new call to layoutget is immediately
invalidated by pnfs_layout_need_return().
To get around this, we should just set plh_return_seq to the current
value of the layout stateid's seqid.

Fixes: d474f96104 ("NFS: Don't return layout segments that are in use")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Trond Myklebust 2021-07-26 07:58:49 -04:00 committed by Anna Schumaker
parent 71d3d0ebc8
commit e20772cbdf
1 changed files with 8 additions and 4 deletions
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12
fs/nfs/pnfs.c
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@ -347,11 +347,15 @@ pnfs_set_plh_return_info(struct pnfs_layout_hdr *lo, enum pnfs_iomode iomode,
iomode = IOMODE_ANY;
lo->plh_return_iomode = iomode;
set_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags);
if (seq != 0) {
WARN_ON_ONCE(lo->plh_return_seq != 0 && lo->plh_return_seq != seq);
/*
* We must set lo->plh_return_seq to avoid livelocks with
* pnfs_layout_need_return()
*/
if (seq == 0)
seq = be32_to_cpu(lo->plh_stateid.seqid);
if (!lo->plh_return_seq || pnfs_seqid_is_newer(seq, lo->plh_return_seq))
lo->plh_return_seq = seq;
pnfs_barrier_update(lo, seq);
}
pnfs_barrier_update(lo, seq);
}
static void