nfs: fix incorrect error handling in LOCALIO

nfs: fix incorrect error handling in LOCALIO

[ Upstream commit ead11ac50ad4b8ef1b64806e962ea984862d96ad ]

nfs4_stat_to_errno() expects a NFSv4 error code as an argument and
returns a POSIX errno.

The problem is LOCALIO is passing nfs4_stat_to_errno() the POSIX errno
return values from filp->f_op->read_iter(), filp->f_op->write_iter()
and vfs_fsync_range().

So the POSIX errno that nfs_local_pgio_done() and
nfs_local_commit_done() are passing to nfs4_stat_to_errno() are
failing to match any NFSv4 error code, which results in
nfs4_stat_to_errno() defaulting to returning -EREMOTEIO. This causes
assertions in upper layers due to -EREMOTEIO not being a valid NFSv4
error code.

Fix this by updating nfs_local_pgio_done() and nfs_local_commit_done()
to use the new nfs_localio_errno_to_nfs4_stat() to map a POSIX errno
to an NFSv4 error code.

Care was taken to factor out nfs4_errtbl_common[] to avoid duplicating
the same NFS error to errno table. nfs4_errtbl_common[] is checked
first by both nfs4_stat_to_errno and nfs_localio_errno_to_nfs4_stat
before they check their own more specialized tables (nfs4_errtbl[] and
nfs4_errtbl_localio[] respectively).

While auditing the associated error mapping tables, the (ab)use of -1
for the last table entry was removed in favor of using ARRAY_SIZE to
iterate the nfs_errtbl[] and nfs4_errtbl[]. And 'errno_NFSERR_IO' was
removed because it caused needless obfuscation.

Fixes: 70ba381e1a431 ("nfs: add LOCALIO support")
Reported-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>