Commit a2915fa0 authored Sep 06, 2021 by Baptiste Lepers Committed by Trond Myklebust Oct 03, 2021

pnfs/flexfiles: Fix misplaced barrier in nfs4_ff_layout_prepare_ds



_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: d67ae825 ("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>

parent 36a10a3c

fs/nfs/flexfilelayout/flexfilelayoutdev.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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.

fs/nfs/pnfs_nfs.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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;