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* [RFC PATCH v1 0/13] Convert NFS client to new fscache-iter API
@ 2020-07-15 15:10 Dave Wysochanski
  2020-07-15 15:10 ` [RFC PATCH v1 01/13] NFS: Clean up nfs_readpage() and nfs_readpages() Dave Wysochanski
                   ` (14 more replies)
  0 siblings, 15 replies; 17+ messages in thread
From: Dave Wysochanski @ 2020-07-15 15:10 UTC (permalink / raw)
  To: Trond Myklebust, Anna Schumaker; +Cc: linux-nfs, linux-cachefs

These patches update the nfs client to use the new FS-Cache API and are at:
https://github.com/DaveWysochanskiRH/kernel/commit/a426b431873ea755c94ccd403aeaba0c4e635016

They are based on David Howells fscache-iter tree at ff12b5a05bd6984ad83e762f702cb655222bad74
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit/?h=fscache-iter&id=ff12b5a05bd6984ad83e762f702cb655222bad74

The following patches may be of specific interest to review
as they are related to the conversion:
NFS: Convert fscache_acquire_cookie and fscache_relinquish_cookie
NFS: Convert nfs_readpage() and readpages() to new fscache API
NFS: Only use and unuse an fscache cookie a single time based on NFS_INO_FSCACHE
NFS: Convert fscache invalidation and update aux_data and i_size

Note that this is only a "first pass" v1 / RFC set I wanted to get
out there for the maintainers to see and know this is being worked on.
It is far from perfect and has some problems still need worked out.
A short summary of this set:

1. Takes a "least invasive to existing code" approach
* most fscache bits stay fs/nfs/fscache.[ch] 
* fscache enable/disable switched inside NFS code on nfs_inode.fscache
* only enable fscache for reads
* may not be the best approach (see future patcheset items below)

2. Basically works and passes a series of tests
* should not affect NFS when fscache is disabled (no "fsc" option)
* a couple small NFS + fscache basic verification tests
* connectathon (all NFS versions, with/without 'fsc' option)
* various iozone tests (all NFS versions, with/without 'fsc' option)

3. Still has a few known problems that are being tracked down
* Data integrity issue when write with O_DIRECT and read
back without O_DIRECT (we get 0's back from the cache)
* iozone tests run through ok but at the end superblock
cookies are left (each NFS version has a different superblock
cookie); this leads to "duplicate cookie" messages
upon subsequent mounts / runs
* A couple oopses in fscache reported to dhowells, may
be related to NFS's enable/disable of fscache on read/write
* Kernel build fails about halfway through with a strange
dubious error at the same place, linking this file:
ld: net/sunrpc/auth_gss/trace.o: attempt to load strings from a non-string section (number 41)


In addition to fixing various code issues and above issues,
a future patchset may:

1. The readpage/readpages conversion patch call read_helpers
directly rather than isolation into fs/nfs/fscache.c
* Similar to the AFS conversion, with calls directly to the
read_helpers, but not sure about non-fsc code path

2. Add write-through support
* Would probably eliminate some problematic code
paths where fscache is turned on / off depending on whether
a file switches from read to write and vice-versa
* This would rework open as well
* Have to work out whether this is possible or not and
with what caveats as far as NFS version support (is this
an NFSv4.x only thing?)

3. Rework dfprintks and/or add ftrace points
* fscache/cachefiles has 'debug' logging similar to rpcdebug
so not sure if we keep rpcdebug here or go full ftrace


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: Rename readpage_async_filler() to nfs_pageio_add_page_read()
  NFS: Convert fscache_acquire_cookie and fscache_relinquish_cookie
  NFS: Allow nfs_async_read_completion_ops to be used by other NFS code
  NFS: Convert nfs_readpage() and readpages() to new fscache API
  NFS: Allow NFS use of new fscache API in build
  NFS: Only use and unuse an fscache cookie a single time based on
    NFS_INO_FSCACHE
  NFS: Convert fscache invalidation and update aux_data and i_size
  NFS: Call nfs_fscache_invalidate() when write extends the size of the
    file

 fs/nfs/Kconfig           |   2 +-
 fs/nfs/file.c            |  20 +--
 fs/nfs/fscache-index.c   |  94 --------------
 fs/nfs/fscache.c         | 315 ++++++++++++++++++++++++-----------------------
 fs/nfs/fscache.h         |  92 +++++---------
 fs/nfs/inode.c           |   1 -
 fs/nfs/internal.h        |   4 +
 fs/nfs/pagelist.c        |   1 +
 fs/nfs/read.c            | 221 ++++++++++++++++-----------------
 fs/nfs/write.c           |   9 +-
 include/linux/nfs_fs.h   |   3 +-
 include/linux/nfs_page.h |   1 +
 include/linux/nfs_xdr.h  |   1 +
 13 files changed, 322 insertions(+), 442 deletions(-)

-- 
1.8.3.1


^ permalink raw reply	[flat|nested] 17+ messages in thread

end of thread, other threads:[~2020-07-17 16:18 UTC | newest]

Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-15 15:10 [RFC PATCH v1 0/13] Convert NFS client to new fscache-iter API Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 01/13] NFS: Clean up nfs_readpage() and nfs_readpages() Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 02/13] NFS: In nfs_readpage() only increment NFSIOS_READPAGES when read succeeds Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 03/13] NFS: Refactor nfs_readpage() and nfs_readpage_async() to use nfs_readdesc Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 04/13] NFS: Call readpage_async_filler() from nfs_readpage_async() Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 05/13] NFS: Add nfs_pageio_complete_read() and remove nfs_readpage_async() Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 06/13] NFS: Rename readpage_async_filler() to nfs_pageio_add_page_read() Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 07/13] NFS: Convert fscache_acquire_cookie and fscache_relinquish_cookie Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 08/13] NFS: Allow nfs_async_read_completion_ops to be used by other NFS code Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 09/13] NFS: Convert nfs_readpage() and readpages() to new fscache API Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 10/13] NFS: Allow NFS use of new fscache API in build Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 11/13] NFS: Only use and unuse an fscache cookie a single time based on NFS_INO_FSCACHE Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 12/13] NFS: Convert fscache invalidation and update aux_data and i_size Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 13/13] NFS: Call nfs_fscache_invalidate() when write extends the size of the file Dave Wysochanski
2020-07-17 14:25 ` [RFC PATCH v1 0/13] Convert NFS client to new fscache-iter API J. Bruce Fields
2020-07-17 15:19 ` [Linux-cachefs] " David Howells
2020-07-17 16:18   ` J. Bruce Fields

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