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[v5,0/3] Convert NFS with fscache to the netfs API

Message ID 20220902125346.1619659-1-dwysocha@redhat.com (mailing list archive)
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Series Convert NFS with fscache to the netfs API | expand

Message

David Wysochanski Sept. 2, 2022, 12:53 p.m. UTC 
This patchset converts NFS with fscache non-direct READ IO paths to
use the netfs API with a non-invasive approach.  The existing NFS pgio
layer does not need extensive changes, and is the best way so far I've
found to address Trond's concerns about modifying the IO path [1] as
well as only enabling netfs when fscache is configured and enabled [2].
I have not attempted performance comparisions to address Chuck
Lever's concern [3] because we are not converting the non-fscache
enabled NFS IO paths to netfs.

The main patch to be reviewed is patch #3 which converts nfs_read_folio
and nfs_readahead.

Changes since v4 (all PATCH3)
- Remove more #ifdefs, replace with stub functions (Jeff Layton)[6]
- Use refcount for last RPC marker (Jeff Layton)[6]

The patches are fairly stable as evidenced with xfstests generic with
various servers, both with and without fscache enabled: 
hammerspace(pNFS flexfiles): vers=4.2,fsc; vers=4.2
NetApp(pNFS filelayout): vers=4.1,fsc; vers=4.0,fsc
RHEL8: vers=3,fsc; vers=3

No major issues outstanding.  Even the previous issue with the
"Subreq overread" was not reproducible with this set.
The known issues are as follows:

1. Unit test setting rsize < readahead does not properly read from
fscache but re-reads data from the NFS server
* This will be fixed with another linux-cachefs [4] patch to resolve
"Stop read optimisation when folio removed from pagecache"
* Daire Byrne also verified the patch fixes his issue as well

2. "Cache volume key already in use" after xfstest runs
* xfstests (hammerspace with vers=4.2,fsc) shows the following on the
console after some tests:
"NFS: Cache volume key already in use (nfs,4.1,2,c50,cfe0100a,3,,,8000,100000,100000,bb8,ea60,7530,ea60,1)"
* This may be fixed with another patch [4] that is in progress

The patchset is based on 6.0-rc3 and has been pushed to github at:
https://github.com/DaveWysochanskiRH/kernel/commits/nfs-fscache-netfs

[1] https://lore.kernel.org/linux-nfs/9cfd5bc3cfc6abc2d3316b0387222e708d67f595.camel@hammerspace.com/
[2] https://lore.kernel.org/linux-nfs/da9200f1bded9b8b078a7aef227fd6b92eb028fb.camel@hammerspace.com/
[3] https://marc.info/?l=linux-nfs&m=160597917525083&w=4
[4] https://www.mail-archive.com/linux-cachefs@redhat.com/msg03043.html
[5] https://marc.info/?l=linux-nfs&m=165962662200679&w=4
[6] https://marc.info/?l=linux-nfs&m=166204800323762&w=4

Dave Wysochanski (3):
  NFS: Rename readpage_async_filler to nfs_pageio_add_page
  NFS: Configure support for netfs when NFS fscache is configured
  NFS: Convert buffered read paths to use netfs when fscache is enabled

 fs/nfs/Kconfig           |   1 +
 fs/nfs/delegation.c      |   2 +-
 fs/nfs/dir.c             |   2 +-
 fs/nfs/fscache.c         | 256 ++++++++++++++++++++++++---------------
 fs/nfs/fscache.h         | 102 ++++++++++------
 fs/nfs/inode.c           |   8 +-
 fs/nfs/internal.h        |  11 +-
 fs/nfs/pagelist.c        |  12 ++
 fs/nfs/pnfs.c            |  12 +-
 fs/nfs/read.c            | 110 ++++++++---------
 fs/nfs/write.c           |   2 +-
 include/linux/nfs_fs.h   |  34 ++++--
 include/linux/nfs_page.h |   3 +
 include/linux/nfs_xdr.h  |   3 +
 14 files changed, 341 insertions(+), 217 deletions(-)