pNFS/flexfiles: When mirrored, retry failed reads by switching mirrors

If the pNFS/flexfiles file is mirrored, and a read to one mirror fails,
then we should bump the mirror index, so that we retry to a different
mirror. Once we've iterated through all mirrors and all failed, we can
return the layout and issue a new LAYOUTGET.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index fbc5a56..7fc14b9 100644 (file)
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -741,17 +741,17 @@ ff_layout_alloc_commit_info(struct pnfs_layout_segment *lseg,
 }
 
 static struct nfs4_pnfs_ds *
-ff_layout_choose_best_ds_for_read(struct nfs_pageio_descriptor *pgio,
+ff_layout_choose_best_ds_for_read(struct pnfs_layout_segment *lseg,
+                                 int start_idx,
                                  int *best_idx)
 {
-       struct nfs4_ff_layout_segment *fls;
+       struct nfs4_ff_layout_segment *fls = FF_LAYOUT_LSEG(lseg);
        struct nfs4_pnfs_ds *ds;
        int idx;
 
-       fls = FF_LAYOUT_LSEG(pgio->pg_lseg);
        /* mirrors are sorted by efficiency */
-       for (idx = 0; idx < fls->mirror_array_cnt; idx++) {
-               ds = nfs4_ff_layout_prepare_ds(pgio->pg_lseg, idx, false);
+       for (idx = start_idx; idx < fls->mirror_array_cnt; idx++) {
+               ds = nfs4_ff_layout_prepare_ds(lseg, idx, false);
                if (ds) {
                        *best_idx = idx;
                        return ds;
@@ -782,7 +782,7 @@ ff_layout_pg_init_read(struct nfs_pageio_descriptor *pgio,
        if (pgio->pg_lseg == NULL)
                goto out_mds;
 
-       ds = ff_layout_choose_best_ds_for_read(pgio, &ds_idx);
+       ds = ff_layout_choose_best_ds_for_read(pgio->pg_lseg, 0, &ds_idx);
        if (!ds)
                goto out_mds;
        mirror = FF_LAYOUT_COMP(pgio->pg_lseg, ds_idx);
@@ -1171,6 +1171,10 @@ static int ff_layout_read_done_cb(struct rpc_task *task,
 
        switch (err) {
        case -NFS4ERR_RESET_TO_PNFS:
+               if (ff_layout_choose_best_ds_for_read(hdr->lseg,
+                                       hdr->pgio_mirror_idx + 1,
+                                       &hdr->pgio_mirror_idx))
+                       goto out_eagain;
                set_bit(NFS_LAYOUT_RETURN_BEFORE_CLOSE,
                        &hdr->lseg->pls_layout->plh_flags);
                pnfs_read_resend_pnfs(hdr);
@@ -1179,11 +1183,13 @@ static int ff_layout_read_done_cb(struct rpc_task *task,
                ff_layout_reset_read(hdr);
                return task->tk_status;
        case -EAGAIN:
-               rpc_restart_call_prepare(task);
-               return -EAGAIN;
+               goto out_eagain;
        }
 
        return 0;
+out_eagain:
+       rpc_restart_call_prepare(task);
+       return -EAGAIN;
 }
 
 static bool