pNFS/flexfiles: Fix an Oopsable condition when connection to the DS fails

If the attempt to connect to a DS fails inside ff_layout_pg_init_read or
ff_layout_pg_init_write, then we currently end up clearing the layout
segment carried by the struct nfs_pageio_descriptor, causing an Oops
when we later call into ff_layout_read_pagelist/ff_layout_write_pagelist.

The fix is to ensure we return the layout and then retry.

Fixes: 446ca2195303 ("pNFS/flexfiles: When initing reads or writes, we...")
Cc: stable@vger.kernel.org # v4.7+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

2 files changed, 28 insertions, 28 deletions

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index ee1c94c7614c..51b51369704c 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -806,11 +806,14 @@ ff_layout_choose_best_ds_for_read(struct pnfs_layout_segment *lseg,
 {
         struct nfs4_ff_layout_segment *fls = FF_LAYOUT_LSEG(lseg);
         struct nfs4_pnfs_ds *ds;
+        bool fail_return = false;
         int idx;
 
         /* mirrors are sorted by efficiency */
         for (idx = start_idx; idx < fls->mirror_array_cnt; idx++) {
-                ds = nfs4_ff_layout_prepare_ds(lseg, idx, false);
+                if (idx+1 == fls->mirror_array_cnt)
+                        fail_return = true;
+                ds = nfs4_ff_layout_prepare_ds(lseg, idx, fail_return);
                 if (ds) {
                         *best_idx = idx;
                         return ds;
@@ -859,6 +862,7 @@ ff_layout_pg_init_read(struct nfs_pageio_descriptor *pgio,
         struct nfs4_pnfs_ds *ds;
         int ds_idx;
 
+retry:
         /* Use full layout for now */
         if (!pgio->pg_lseg)
                 ff_layout_pg_get_read(pgio, req, false);
@@ -871,10 +875,13 @@ ff_layout_pg_init_read(struct nfs_pageio_descriptor *pgio,
 
         ds = ff_layout_choose_best_ds_for_read(pgio->pg_lseg, 0, &ds_idx);
         if (!ds) {
-                if (ff_layout_no_fallback_to_mds(pgio->pg_lseg))
-                        goto out_pnfs;
-                else
+                if (!ff_layout_no_fallback_to_mds(pgio->pg_lseg))
                         goto out_mds;
+                pnfs_put_lseg(pgio->pg_lseg);
+                pgio->pg_lseg = NULL;
+                /* Sleep for 1 second before retrying */
+                ssleep(1);
+                goto retry;
         }
 
         mirror = FF_LAYOUT_COMP(pgio->pg_lseg, ds_idx);
@@ -890,12 +897,6 @@ out_mds:
         pnfs_put_lseg(pgio->pg_lseg);
         pgio->pg_lseg = NULL;
         nfs_pageio_reset_read_mds(pgio);
-        return;
-
-out_pnfs:
-        pnfs_set_lo_fail(pgio->pg_lseg);
-        pnfs_put_lseg(pgio->pg_lseg);
-        pgio->pg_lseg = NULL;
 }
 
 static void
@@ -909,6 +910,7 @@ ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
         int i;
         int status;
 
+retry:
         if (!pgio->pg_lseg) {
                 pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
                                                    req->wb_context,
@@ -940,10 +942,13 @@ ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
         for (i = 0; i < pgio->pg_mirror_count; i++) {
                 ds = nfs4_ff_layout_prepare_ds(pgio->pg_lseg, i, true);
                 if (!ds) {
-                        if (ff_layout_no_fallback_to_mds(pgio->pg_lseg))
-                                goto out_pnfs;
-                        else
+                        if (!ff_layout_no_fallback_to_mds(pgio->pg_lseg))
                                 goto out_mds;
+                        pnfs_put_lseg(pgio->pg_lseg);
+                        pgio->pg_lseg = NULL;
+                        /* Sleep for 1 second before retrying */
+                        ssleep(1);
+                        goto retry;
                 }
                 pgm = &pgio->pg_mirrors[i];
                 mirror = FF_LAYOUT_COMP(pgio->pg_lseg, i);
@@ -956,12 +961,6 @@ out_mds:
         pnfs_put_lseg(pgio->pg_lseg);
         pgio->pg_lseg = NULL;
         nfs_pageio_reset_write_mds(pgio);
-        return;
-
-out_pnfs:
-        pnfs_set_lo_fail(pgio->pg_lseg);
-        pnfs_put_lseg(pgio->pg_lseg);
-        pgio->pg_lseg = NULL;
 }
 
 static unsigned int
diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
index 970efba05ae1..f7a3f6b05369 100644
--- a/fs/nfs/flexfilelayout/flexfilelayoutdev.c
+++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
@@ -379,7 +379,7 @@ nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx,
 
         devid = &mirror->mirror_ds->id_node;
         if (ff_layout_test_devid_unavailable(devid))
-                goto out;
+                goto out_fail;
 
         ds = mirror->mirror_ds->ds;
         /* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */
@@ -405,15 +405,16 @@ nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx,
                         mirror->mirror_ds->ds_versions[0].rsize = max_payload;
                 if (mirror->mirror_ds->ds_versions[0].wsize > max_payload)
                         mirror->mirror_ds->ds_versions[0].wsize = max_payload;
-        } else {
-                ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
-                                         mirror, lseg->pls_range.offset,
-                                         lseg->pls_range.length, NFS4ERR_NXIO,
-                                         OP_ILLEGAL, GFP_NOIO);
-                if (fail_return || !ff_layout_has_available_ds(lseg))
-                        pnfs_error_mark_layout_for_return(ino, lseg);
-                ds = NULL;
+                goto out;
         }
+        ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
+                                 mirror, lseg->pls_range.offset,
+                                 lseg->pls_range.length, NFS4ERR_NXIO,
+                                 OP_ILLEGAL, GFP_NOIO);
+out_fail:
+        if (fail_return || !ff_layout_has_available_ds(lseg))
+                pnfs_error_mark_layout_for_return(ino, lseg);
+        ds = NULL;
 out:
         return ds;
 }