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From:   Dave Wysochanski <dwysocha@redhat.com>
To:     Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>
Cc:     linux-nfs@vger.kernel.org, dhowells@redhat.com
Subject: [PATCH v1 0/13] Convert NFS to new netfs and fscache APIs
Date:   Sat, 21 Nov 2020 08:29:08 -0500
Message-Id: <1605965348-24468-1-git-send-email-dwysocha@redhat.com>
Precedence: bulk

These patches update the NFS client to use the new netfs and fscache
APIs and are at:
https://github.com/DaveWysochanskiRH/kernel.git
https://github.com/DaveWysochanskiRH/kernel/commit/94e9633d98a5542ea384b1095290ac6f915fc917
https://github.com/DaveWysochanskiRH/kernel/releases/tag/fscache-iter-nfs-20201120

The patches are based on David Howells fscache-iter tree at
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-iter

The first 6 patches refactor some of the NFS read code to facilitate
re-use, the next 6 patches do the conversion to the new API, and the
last patch is a somewhat awkward fix for a problem seen in final
testing.

Per David Howell's recent post, note that the new fscache API is
divided into two separate APIs, a 'netfs' API and an 'fscache' API.
The netfs API was done to help simplify the IO paths of network
filesystems, and can be called even when fscache is disabled, thus
simplifing both readpage and readahead implementations.  However,
for now these NFS conversion patches only call the netfs API when
fscache is enabled, similar to the existing NFS code.

Trond and Anna, I would appreciate your guidance on this patchset.
At least I would like your feedback regarding the direction
you would like these patches to go, in particular, the following
items:

1. Whether you are ok with using the netfs API unconditionally even
when fscache is disabled, or prefer this "least invasive to NFS"
approach.  Note the unconditional use of the netfs API is the
recommended approach per David's post and the AFS and CEPH
implementations, but I was unsure if you would accept this
approach or would prefer to minimize changes to NFS.  Note if
we keep the current approach to minimize NFS changes, we will
have to address some problems with page unlocking such as with
patch 13 in the series.

2. Whether to keep the NFS fscache implementation as "read only"
or if we add write through support.  Today we only enable fscache
when a file is open read-only and disable / invalidate when a file
is open for write.

Still TODO
1. Address known issues (lockdep, page unlocking), depending on
what is decided as far as implementation direction
  a) nfs_issue_op: takes rcu_read_lock but may calls nfs_page_alloc()
  with GFP_KERNEL which may sleep (dhowells noted this in a review)
  b) nfs_refresh_inode() takes inode->i_lock but may call
  __fscache_invalidate() which may sleep (found with lockdep)
2. Fixup NFS fscache stats (NFSIOS_FSCACHE_*)
* Compare with netfs stats and determine if still needed
3. Cleanup dfprintks and/or convert to tracepoints
4. Further tests (see "Not tested yet")

Checks run
1. checkpatch: PASS*
  * a few warnings, mostly trivial fixups, some unrelated to this set
2. kernel builds with each patch: PASS
  * each patch in series built cleanly which ensure bisection

Tests run
1. Custom NFS+fscache unit tests for basic operation: PASS*
  * no oops or data corruptions
  * Some op counts are a bit off but these are mostly due
    to statistics not implemented properly (NFSIOS_FSCACHE_*)
2. cthon04: PASS (test options "-b -g -s -l", fsc,vers=3,4.0,4.1,4.2,sec=sys)
* No failures or oopses for any version or test options
3. iozone tests (fsc,vers=3,4.0,4.1,4.2,sec=sys): PASS
* No failures or oopses
4. kernel build (fsc,vers=3,4.1,4.2): PASS*
  * all builds finish without errors or data corruption
  * one lockdep "scheduling while atomic" fired with NFS41 and
    was due to one an fscache invalidation code path (known issue 'b' above)
5. xfstests/generic (fsc,vers=4.2, nofsc,vers=4.2): PASS*
   * generic/013 (pass but triggers i_lock lockdep warning known issue 'a' above)
   * NOTE: The following tests failed with errors, but they
     also fail on vanilla 5.10-rc4 so are not related to this
     patchset
     * generic/074 (lockep invalid wait context - nfs_free_request())
     * generic/538 (short read)
     * generic/551 (pread: Unknown error 524, Data verification fail)
     * generic/568 (ERROR: File grew from 4096 B to 8192 B when writing to the fallocated range)

Not tested yet:
* error injections (for example, connection disruptions, server errors during IO, etc)
* pNFS
* many process mixed read/write on same file
* performance
Dave Wysochanski (13):
  NFS: Clean up nfs_readpage() and nfs_readpages()
  NFS: In nfs_readpage() only increment NFSIOS_READPAGES when read
    succeeds
  NFS: Refactor nfs_readpage() and nfs_readpage_async() to use
    nfs_readdesc
  NFS: Call readpage_async_filler() from nfs_readpage_async()
  NFS: Add nfs_pageio_complete_read() and remove nfs_readpage_async()
  NFS: Allow internal use of read structs and functions
  NFS: Convert fscache_acquire_cookie and fscache_relinquish_cookie
  NFS: Convert fscache_enable_cookie and fscache_disable_cookie
  NFS: Convert fscache invalidation and update aux_data and i_size
  NFS: Convert to the netfs API and nfs_readpage to use netfs_readpage
  NFS: Convert readpage to readahead and use netfs_readahead for fscache
  NFS: Allow NFS use of new fscache API in build
  NFS: Ensure proper page unlocking when reads fail with retryable
    errors

 fs/nfs/Kconfig             |   2 +-
 fs/nfs/direct.c            |   2 +
 fs/nfs/file.c              |  22 ++--
 fs/nfs/fscache-index.c     |  94 --------------
 fs/nfs/fscache.c           | 315 ++++++++++++++++++++-------------------------
 fs/nfs/fscache.h           | 132 +++++++------------
 fs/nfs/inode.c             |   4 +-
 fs/nfs/internal.h          |   8 ++
 fs/nfs/nfs4proc.c          |   2 +-
 fs/nfs/pagelist.c          |   2 +
 fs/nfs/read.c              | 248 ++++++++++++++++-------------------
 fs/nfs/write.c             |   3 +-
 include/linux/nfs_fs.h     |   5 +-
 include/linux/nfs_iostat.h |   2 +-
 include/linux/nfs_page.h   |   1 +
 include/linux/nfs_xdr.h    |   1 +
 16 files changed, 339 insertions(+), 504 deletions(-)

-- 
1.8.3.1