pNFS/flexfiles: Add support for FF_FLAGS_NO_IO_THRU_MDS
For loosely coupled pNFS/flexfiles systems, there is often no advantage
at all in going through the MDS for I/O, since the MDS is subject to
the same limitations as all other clients when talking to DSes. If a
DS is unresponsive, I/O through the MDS will fail.
For such systems, the only scalable solution is to have the pNFS clients
retry doing pNFS, and so the protocol now provides a flag that allows
the pNFS server to signal this.
If LAYOUTGET returns FF_FLAGS_NO_IO_THRU_MDS, then we should assume that
the MDS wants the client to retry using these devices, even if they were
previously marked as being unavailable. To do so, we add a helper,
ff_layout_mark_devices_valid() that will be called from 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 7fc14b9..03516c8 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -339,6 +339,19 @@
}
}
+static void ff_layout_mark_devices_valid(struct nfs4_ff_layout_segment *fls)
+{
+ struct nfs4_deviceid_node *node;
+ int i;
+
+ if (!(fls->flags & FF_FLAGS_NO_IO_THRU_MDS))
+ return;
+ for (i = 0; i < fls->mirror_array_cnt; i++) {
+ node = &fls->mirror_array[i]->mirror_ds->id_node;
+ clear_bit(NFS_DEVICEID_UNAVAILABLE, &node->flags);
+ }
+}
+
static struct pnfs_layout_segment *
ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
struct nfs4_layoutget_res *lgr,
@@ -499,6 +512,7 @@
rc = ff_layout_check_layout(lgr);
if (rc)
goto out_err_free;
+ ff_layout_mark_devices_valid(fls);
ret = &fls->generic_hdr;
dprintk("<-- %s (success)\n", __func__);
@@ -1035,7 +1049,8 @@
rpc_wake_up(&tbl->slot_tbl_waitq);
/* fall through */
default:
- if (ff_layout_has_available_ds(lseg))
+ if (ff_layout_no_fallback_to_mds(lseg) ||
+ ff_layout_has_available_ds(lseg))
return -NFS4ERR_RESET_TO_PNFS;
reset:
dprintk("%s Retry through MDS. Error %d\n", __func__,
@@ -1153,7 +1168,6 @@
}
/* NFS_PROTO call done callback routines */
-
static int ff_layout_read_done_cb(struct rpc_task *task,
struct nfs_pgio_header *hdr)
{