[PATCH 00/21] NFS: flexfiles device notifications and caching for wide striped layouts

[Benjamin Coddington <ben.coddington@hammerspace.com>]

A flexfiles layout striped across many data servers puts hundreds to
~1000 distinct deviceIDs in play for a single mount.  This series makes
the client's CB_NOTIFY_DEVICEID handling actually work under live
layouts, implements the deviceID-deletion race recovery RFC 8881 asks
for, and scales the device caches to that number of devices.

Patches 1-4 are standalone fixes (Cc: stable) for latent bugs in the
striped-layout paths.  The CB_NOTIFY_DEVICEID decoder gated consuming
ndc_immediate on the layout type instead of the notification type, so
the flag was silently lost and any multi-item cnda_changes<> array
misaligned after the first entry.  Read data-server selection truncated
the file offset to 32 bits, picking the wrong stripe's DS for
availability probing and coalescing above 4 GiB.  And page coalescing
was bounded on a segment-relative offset in both the flexfiles and files
layouts, so an unaligned segment let a coalesced I/O straddle a stripe
boundary and send the bytes past it to the wrong data server.

Patches 5-13 make CHANGE notifications work under live layouts.  RFC 8881
Section 12.2.10 has CB_NOTIFY_DEVICEID CHANGE exist precisely so a server
can re-point a deviceID without recalling the layouts that reference it,
but the client's only response today is to unhash the cached device --
which never reaches the references pinned inside the layout driver's
segments, so I/O keeps going to the old mapping until the layouts are
freed.  Each in-flight I/O is given its own device-node reference, the
mirror's pinned pointer becomes RCU-managed, and a new layout-driver
hook re-resolves the device in place, honoring ndc_immediate.  A
GETDEVICEINFO reply that raced a CHANGE is discarded rather than
installed stale.

Patches 14-17 implement the deviceID-deletion race of RFC 8881 Section
18.40.4: layouts still referencing a deleted deviceID are tested with
TEST_STATEID, revoked state is recovered, and the deletion is confirmed
with GETDEVICEINFO before escalating to lease recovery.  A DELETE that
no live layout references keeps today's cheap path.

Patches 18-21 scale the device caches.  The global deviceid hash grows
from 32 to 256 buckets (a load factor of ~31 at 1000 devices today), and
the per-net data-server cache moves from a single list to hash buckets
keyed by the DS address set -- which also fixes a latent aliasing bug,
since the old comparator matched on subset rather than equality and
merged two data servers whenever one's address set contained the other's.
Last, the flexfiles driver gains a dataserver_nconnect module parameter
alongside its existing dataserver_timeo and dataserver_retrans knobs:
data-server clients otherwise inherit the MDS nconnect, which at ~1000
DSes and nconnect=16 means ~16k sockets and their slot tables for little
gain on a workload striping across the DSes anyway.  It defaults to 0,
preserving today's inherit-from-MDS behavior.

Tested end-to-end against reffs, a notification-capable reference
server, at 256 and 1000 devices, including KASAN and lockdep runs under
concurrent notification storms.

A related series, "NFS: size the LAYOUTGET reply buffer for wide
flexfiles layouts", lifts the single-page LAYOUTGET reply buffer that
today caps a segment at roughly 28 stripes.  The two are independent and
apply cleanly in either order.

Benjamin Coddington (21):
  pNFS: Fix CB_NOTIFY_DEVICEID CHANGE to consume ndc_immediate
  NFSv4/flexfiles: Use the full 64-bit offset for read DS selection
  NFSv4/flexfiles: Bound page coalescing on the absolute stripe offset
  NFSv4/filelayout: Anchor page coalescing on pattern_offset
  NFSv4/flexfiles: Reference the device node across DS setup
  NFSv4/flexfiles: Carry the device node reference across each I/O
  NFSv4/flexfiles: Hold a device node reference for layoutstats encoding
  NFSv4/flexfiles: Make the pinned device node pointer RCU-managed
  pNFS: Add a reresolve_deviceid layout driver hook
  NFSv4/flexfiles: Implement in-place device re-resolve on CHANGE
  NFSv4: Dispatch CB_NOTIFY_DEVICEID CHANGE to an in-place refresh
  NFSv4/flexfiles: Honor ndc_immediate on CB_NOTIFY_DEVICEID CHANGE
  pNFS: Discard a GETDEVICEINFO reply that raced a CHANGE notification
  pNFS: Add deviceid reference query and collection walkers
  NFSv4/pnfs: Recover revoked layouts on a deleted deviceID
  NFSv4/pnfs: Confirm a deviceID delete via GETDEVICEINFO
  NFSv4/pnfs: Dispatch CB_NOTIFY_DEVICEID DELETE to race recovery
  NFSv4/pnfs: Grow the deviceid cache hash table
  NFSv4/pnfs: Re-home the data-server cache onto hash buckets
  NFSv4/pnfs: Key the data-server cache by its address set
  NFSv4/flexfiles: Add a dataserver_nconnect cap

 fs/nfs/callback_proc.c                    |  30 +-
 fs/nfs/callback_xdr.c                     |   2 +-
 fs/nfs/client.c                           |   6 +-
 fs/nfs/filelayout/filelayout.c            |   8 +-
 fs/nfs/filelayout/filelayoutdev.c         |   2 +-
 fs/nfs/flexfilelayout/flexfilelayout.c    | 383 ++++++++++++++--------
 fs/nfs/flexfilelayout/flexfilelayout.h    |  44 +--
 fs/nfs/flexfilelayout/flexfilelayoutdev.c | 193 +++++++----
 fs/nfs/internal.h                         |   3 +-
 fs/nfs/netns.h                            |   5 +-
 fs/nfs/nfs3client.c                       |   9 +-
 fs/nfs/nfs4_fs.h                          |   2 +
 fs/nfs/nfs4client.c                       |   7 +-
 fs/nfs/nfs4proc.c                         | 113 +++++++
 fs/nfs/nfs4state.c                        |   3 +
 fs/nfs/pnfs.c                             | 292 +++++++++++++++++
 fs/nfs/pnfs.h                             |  81 ++++-
 fs/nfs/pnfs_dev.c                         |  35 +-
 fs/nfs/pnfs_nfs.c                         |  93 +++++-
 include/linux/nfs_fs_sb.h                 |   2 +
 include/linux/nfs_xdr.h                   |   2 +
 21 files changed, 1069 insertions(+), 246 deletions(-)

base-commit: db2ddb87143519e20a95aa36c60b36107b736a58
-- 
2.53.0