[PATCH 00/10] Convert NFS fscache read paths to netfs API

[Dave Wysochanski <dwysocha@redhat.com>]

This minimal set of patches update the NFS client to use the new
readahead method, and convert the NFS fscache to use the new netfs
IO API, and are at:
https://github.com/DaveWysochanskiRH/kernel/releases/tag/fscache-iter-lib-nfs-20210128
https://github.com/DaveWysochanskiRH/kernel/commit/74357eb291c9c292f3ab3bc9ed1227cb76f52c51

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

The first 6 patches refactor some of the NFS read code to facilitate
re-use, the next 4 patches do the conversion to the new API.  Note
patch 8 converts nfs_readpages to nfs_readahead.

Changes since my last posting on Jan 27, 2021
- Fix oops with fscache enabled on parallel read unit test
- Add patches to handle invalidate and releasepage
- Use #define FSCACHE_USE_NEW_IO_API to select the new API
- Minor cleanup in nfs_readahead_from_fscache

Still TODO
1. Fix known bugs
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)
c) WARN with xfstest fscache/netapp/pnfs/nfs41
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")

Tests run
1. Custom NFS+fscache unit tests for basic operation: PASS
* vers=3,4.0,4.1,4.2,sec=sys,server=localhost (same kernel)
2. cthon04: PASS
* test options "-b -g -s -l", fsc,vers=3,4.0,4.1,4.2,sec=sys
* No failures, oopses or hangs
3. iozone tests: PASS
* nofsc,fsc,vers=3,4.0,4.1,4.2,sec=sys,server=rhel7,rhel8
* No failures, oopses, or hangs
4. xfstests/generic: PASS*
* no hangs or crashes (one WARN); failures unrelated to these patches
* Ran following configurations
  * vers=4.1,fsc,sec=sys,rhel7-server: PASS
  * vers=4.0,fsc,sec=sys,rhel7-server: PASS
  * vers=3,fsc,sec=sys,rhel7-server: PASS
  * vers=4.1,nofsc,sec=sys,netapp-server(pnfs/files): PASS
  * vers=4.1,fsc,sec=sys,netapp-server(pnfs/files): INCOMPLETE
    * WARN_ON fs/netfs/read_helper.c:616
    * ran with kernel.panic_on_oops=1
  * vers=4.2,fsc,sec=sys,rhel7-server: running at generic/438
  * vers=4.2,fsc,sec=sys,rhel8-server: running at generic/127
5. kernel build: PASS
  * vers=4.2,fsc,sec=sys,rhel8-server: PASS

Not tested yet:
* error injections (for example, connection disruptions, server errors during IO, etc)
* many process mixed read/write on same file
* performance

Dave Wysochanski (10):
  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 to the netfs API and nfs_readpage to use netfs_readpage
  NFS: Convert readpages to readahead and use netfs_readahead for
    fscache
  NFS: Update releasepage to handle new fscache kiocb IO API
  NFS: update various invalidation code paths for new IO API

 fs/nfs/file.c              |  22 +++--
 fs/nfs/fscache.c           | 230 +++++++++++++++++++------------------------
 fs/nfs/fscache.h           | 105 +++-----------------
 fs/nfs/internal.h          |   8 ++
 fs/nfs/pagelist.c          |   2 +
 fs/nfs/read.c              | 240 ++++++++++++++++++++-------------------------
 fs/nfs/write.c             |  10 +-
 include/linux/nfs_fs.h     |   5 +-
 include/linux/nfs_iostat.h |   2 +-
 include/linux/nfs_page.h   |   1 +
 include/linux/nfs_xdr.h    |   1 +
 11 files changed, 257 insertions(+), 369 deletions(-)

-- 
1.8.3.1