[PATCH 5.14 679/849] pnfs/flexfiles: Fix misplaced barrier in nfs4_ff_layout_prepare_ds

Greg Kroah-Hartman
2021-11-15T23:21:43Z

From: Baptiste Lepers <baptiste.lepers@gmail.com>

[ 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 <baptiste.lepers@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 c9b61b818ec11..bfa7202ca7be1 100644
--- a/fs/nfs/flexfilelayout/flexfilelayoutdev.c
+++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
@@ -378,10 +378,10 @@ nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
goto noconnect;

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 cf19914fec817..02bd6e83961d9 100644
--- a/fs/nfs/pnfs_nfs.c
+++ b/fs/nfs/pnfs_nfs.c
@@ -895,7 +895,7 @@ 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;
@@ -973,7 +973,7 @@ 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