Implement support for multiple extents in the LAYOUTGET response
for two main reasons.
First, it avoids unnecessary RPC calls. For files consisting of many
extents, especially large ones, too many LAYOUTGET requests are observed
in Wireshark traces.
Second, due to the current limitation on returning a single extent,
the client can only reliably request layouts with minimum length set
to 4K. Otherwise, NFS4ERR_LAYOUTUNAVAILABLE may be returned if XFS
allocated a 4K extent within the requested range.
We are using the ability to request layouts with a minimum length
greater than 4K to fix/workaround a bug in the client. I will prepare
the client's patch for review too.
Below is an example of multiple extents in the LAYOUTGET response
captured using Wireshark.
Network File System, Ops(3): SEQUENCE, PUTFH, LAYOUTGET
[Program Version: 4]
[V4 Procedure: COMPOUND (1)]
Tag: <EMPTY>
length: 0
contents: <EMPTY>
minorversion: 2
Operations (count: 3): SEQUENCE, PUTFH, LAYOUTGET
Opcode: SEQUENCE (53)
Opcode: PUTFH (22)
Opcode: LAYOUTGET (50)
layout available?: No
layout type: LAYOUT4_BLOCK_VOLUME (3)
IO mode: IOMODE_RW (2)
offset: 0
length: 10485760
min length: 16384
StateID
maxcount: 4096
[Main Opcode: LAYOUTGET (50)]
Network File System, Ops(3): SEQUENCE PUTFH LAYOUTGET
[Program Version: 4]
[V4 Procedure: COMPOUND (1)]
Status: NFS4_OK (0)
Tag: <EMPTY>
length: 0
contents: <EMPTY>
Operations (count: 3)
Opcode: SEQUENCE (53)
Opcode: PUTFH (22)
Opcode: LAYOUTGET (50)
Status: NFS4_OK (0)
return on close?: Yes
StateID
Layout Segment (count: 1)
offset: 0
length: 385024
IO mode: IOMODE_RW (2)
layout type: LAYOUT4_BLOCK_VOLUME (3)
layout: <DATA>
length: 4052
contents: <DATA>
[Main Opcode: LAYOUTGET (50)]
pNFS Block Layout Extents
bex_count: 92
BEX[0]
BEX[1]
BEX[2]
...
Signed-off-by: Sergey Bashirov <sergeybashirov@gmail.com>
---
Changes in v3:
- Added a Fixes tag
- Removed an unnecessary sentence from the commit message
Sergey Bashirov (4):
NFSD/blocklayout: Fix minlength check in proc_layoutget
NFSD/blocklayout: Extract extent mapping from proc_layoutget
NFSD/blocklayout: Introduce layout content structure
NFSD/blocklayout: Support multiple extents per LAYOUTGET
fs/nfsd/blocklayout.c | 154 +++++++++++++++++++++++++++------------
fs/nfsd/blocklayoutxdr.c | 36 ++++++---
fs/nfsd/blocklayoutxdr.h | 14 ++++
3 files changed, 147 insertions(+), 57 deletions(-)
--
2.43.0