From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Fri, 18 Sep 2020 08:58:58 -0400
Subject: [PATCH] pNFS/flexfiles: Ensure we initialise the mirror bsizes
 correctly on read
Git-commit: ee15c7b53e52fb04583f734461244c4dcca828fa
Patch-mainline: v5.9-rc8
References: git-fixes

While it is true that reading from an unmirrored source always uses
index 0, that is no longer true for mirrored sources when we fail over.

Fixes: 563c53e73b8b ("NFS: Fix flexfiles read failover")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/flexfilelayout/flexfilelayout.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -908,6 +908,7 @@ ff_layout_pg_init_read(struct nfs_pageio
 	struct nfs4_ff_layout_mirror *mirror;
 	struct nfs4_pnfs_ds *ds;
 	int ds_idx;
+	u32 i;
 
 retry:
 	pnfs_generic_pg_check_layout(pgio);
@@ -934,14 +935,14 @@ retry:
 		goto retry;
 	}
 
-	mirror = FF_LAYOUT_COMP(pgio->pg_lseg, ds_idx);
+	for (i = 0; i < pgio->pg_mirror_count; i++) {
+		mirror = FF_LAYOUT_COMP(pgio->pg_lseg, i);
+		pgm = &pgio->pg_mirrors[i];
+		pgm->pg_bsize = mirror->mirror_ds->ds_versions[0].rsize;
+	}
 
 	pgio->pg_mirror_idx = ds_idx;
 
-	/* read always uses only one mirror - idx 0 for pgio layer */
-	pgm = &pgio->pg_mirrors[0];
-	pgm->pg_bsize = mirror->mirror_ds->ds_versions[0].rsize;
-
 	if (NFS_SERVER(pgio->pg_inode)->flags &
 			(NFS_MOUNT_SOFT|NFS_MOUNT_SOFTERR))
 		pgio->pg_maxretrans = io_maxretrans;