[0/3] nfsd: write verifier fixes and optimization

Message

Jeff Layton Feb. 13, 2023, 9:13 p.m. UTC

While looking at the recent problems with the fsync during nfsd_file
cleanup, it occured to me that we could greatly simplify and improve
the server's write verifier handling. I also noticed an existing bug
which is fixed in patch #1.

Instead of trying to check for errors via fsync and resetting the write
verifier when we get one, we can just fold the current value of the
inode's errseq_t into the hashed verifier that is generated at startup
time.

Testing this new scheme has been a real challenge. Once a writeback
error is recorded on all local filesystems, further attempts to write to
the inode return -EIO (and some filesystems even flip to r/o) and you
never see the new verifier.

Trond, you originally added the code to make it reset the verifier on a
writeback error. Do you have a good way to test that? Did you guys use
NFSv3 reexport for testing this somehow?

Jeff Layton (3):
  nfsd: copy the whole verifier in nfsd_copy_write_verifier
  errseq: add a new errseq_fetch helper
  nfsd: simplify write verifier handling

 fs/nfsd/filecache.c    | 22 +------------------
 fs/nfsd/netns.h        |  4 ----
 fs/nfsd/nfs4proc.c     | 17 ++++++---------
 fs/nfsd/nfsctl.c       |  1 -
 fs/nfsd/nfssvc.c       | 48 +++++++++++++-----------------------------
 fs/nfsd/trace.h        | 28 ------------------------
 fs/nfsd/vfs.c          | 28 +++++-------------------
 fs/nfsd/vfs.h          |  1 +
 include/linux/errseq.h |  1 +
 lib/errseq.c           | 33 ++++++++++++++++++++++++++++-
 10 files changed, 62 insertions(+), 121 deletions(-)