nfsd: fix nfs read eof detection

Currently, the knfsd server assumes that a short read indicates an
end of file. That assumption is incorrect. The short read means that
either we've hit the end of file, or we've hit a read error.

In the case of a read error, the client may want to retry (as per the
implementation recommendations in RFC1813 and RFC7530), but currently it
is being told that it hit an eof.

Move the code to detect eof from version specific code into the generic
nfsd read.

Report eof only in the two following cases:
1) read() returns a zero length short read with no error.
2) the offset+length of the read is >= the file size.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 3 insertions, 8 deletions

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index c1fc2641e3e7..533d0fc3c96b 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3472,7 +3472,7 @@ static __be32 nfsd4_encode_splice_read(
 
 	len = maxcount;
 	nfserr = nfsd_splice_read(read->rd_rqstp, read->rd_fhp,
-				  file, read->rd_offset, &maxcount);
+				  file, read->rd_offset, &maxcount, &eof);
 	read->rd_length = maxcount;
 	if (nfserr) {
 		/*
@@ -3484,9 +3484,6 @@ static __be32 nfsd4_encode_splice_read(
 		return nfserr;
 	}
 
-	eof = nfsd_eof_on_read(len, maxcount, read->rd_offset,
-				d_inode(read->rd_fhp->fh_dentry)->i_size);
-
 	*(p++) = htonl(eof);
 	*(p++) = htonl(maxcount);
 
@@ -3557,15 +3554,13 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 
 	len = maxcount;
 	nfserr = nfsd_readv(resp->rqstp, read->rd_fhp, file, read->rd_offset,
-			    resp->rqstp->rq_vec, read->rd_vlen, &maxcount);
+			    resp->rqstp->rq_vec, read->rd_vlen, &maxcount,
+			    &eof);
 	read->rd_length = maxcount;
 	if (nfserr)
 		return nfserr;
 	xdr_truncate_encode(xdr, starting_len + 8 + ((maxcount+3)&~3));
 
-	eof = nfsd_eof_on_read(len, maxcount, read->rd_offset,
-				d_inode(read->rd_fhp->fh_dentry)->i_size);
-
 	tmp = htonl(eof);
 	write_bytes_to_xdr_buf(xdr->buf, starting_len    , &tmp, 4);
 	tmp = htonl(maxcount);