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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>
This commit is contained in:
Trond Myklebust 2015-11-02 09:59:00 -05:00
parent 135444126a
commit 260074cd84
2 changed files with 23 additions and 2 deletions
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18
fs/nfs/flexfilelayout/flexfilelayout.c
View File

@ -339,6 +339,19 @@ static void ff_layout_sort_mirrors(struct nfs4_ff_layout_segment *fls)
}
}
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 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
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 @@ static int ff_layout_async_handle_error_v4(struct rpc_task *task,
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 @@ static void ff_layout_io_track_ds_error(struct pnfs_layout_segment *lseg,
}
/* NFS_PROTO call done callback routines */
static int ff_layout_read_done_cb(struct rpc_task *task,
struct nfs_pgio_header *hdr)
{

7
fs/nfs/flexfilelayout/flexfilelayout.h
View File

@ -10,6 +10,7 @@
#define FS_NFS_NFS4FLEXFILELAYOUT_H
#define FF_FLAGS_NO_LAYOUTCOMMIT 1
#define FF_FLAGS_NO_IO_THRU_MDS 2
#include "../pnfs.h"
@ -145,6 +146,12 @@ FF_LAYOUT_MIRROR_COUNT(struct pnfs_layout_segment *lseg)
return FF_LAYOUT_LSEG(lseg)->mirror_array_cnt;
}
static inline bool
ff_layout_no_fallback_to_mds(struct pnfs_layout_segment *lseg)
{
return FF_LAYOUT_LSEG(lseg)->flags & FF_FLAGS_NO_IO_THRU_MDS;
}
static inline bool
ff_layout_test_devid_unavailable(struct nfs4_deviceid_node *node)
{