# \[PATCH 4.9 131/207\] pnfs/flexfiles: Fix misplaced barrier in nfs4\_ff\_layout\_prepare\_ds - From: Greg Kroah-Hartman \ - Date: 2021-11-24 12:23:27 - List: stable - Page: https://ratatoskr.run/stable/2021/11/1584068 - Thread: https://ratatoskr.run/stable/2021/11/1583929/t/2.md ```text From: Baptiste Lepers [ Upstream commit a2915fa06227b056a8f9b0d79b61dca08ad5cfc6 ] _nfs4_pnfs_v3/v4_ds_connect do some work smp_wmb ds->ds_clp = clp; And nfs4_ff_layout_prepare_ds currently does smp_rmb if(ds->ds_clp) ... This patch places the smp_rmb after the if. This ensures that following reads only happen once nfs4_ff_layout_prepare_ds has checked that data has been properly initialized. Fixes: d67ae825a59d6 ("pnfs/flexfiles: Add the FlexFile Layout Driver") Signed-off-by: Baptiste Lepers Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin --- fs/nfs/flexfilelayout/flexfilelayoutdev.c | 4 ++-- fs/nfs/pnfs_nfs.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c b/fs/nfs/flexfilelayout/flexfilelayoutdev.c index c8863563c6350..287ed99a7e513 100644 --- a/fs/nfs/flexfilelayout/flexfilelayoutdev.c +++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c @@ -383,10 +383,10 @@ nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx, goto out_fail; ds = mirror->mirror_ds->ds; + if (READ_ONCE(ds->ds_clp)) + goto out; /* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */ smp_rmb(); - if (ds->ds_clp) - goto out; /* FIXME: For now we assume the server sent only one version of NFS * to use for the DS. diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c index 53b4705abcc76..1f2da20946640 100644 --- a/fs/nfs/pnfs_nfs.c +++ b/fs/nfs/pnfs_nfs.c @@ -666,7 +666,7 @@ static int _nfs4_pnfs_v3_ds_connect(struct nfs_server *mds_srv, } smp_wmb(); - ds->ds_clp = clp; + WRITE_ONCE(ds->ds_clp, clp); dprintk("%s [new] addr: %s\n", __func__, ds->ds_remotestr); out: return status; @@ -742,7 +742,7 @@ static int _nfs4_pnfs_v4_ds_connect(struct nfs_server *mds_srv, } smp_wmb(); - ds->ds_clp = clp; + WRITE_ONCE(ds->ds_clp, clp); dprintk("%s [new] addr: %s\n", __func__, ds->ds_remotestr); out: return status; -- 2.33.0 ```