[PATCH 2/6] NFSD: Apply per-export I/O modes to READ and WRITE

[Jeff Layton]

Resolve each export's effective I/O mode (explicit setting, else the
global io_cache_read/write knob) in nfsd_iter_read and nfsd_vfs_write,
and skip splice for reads on exports whose effective read mode is not
buffered. Update the debugfs knob comments to match.

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
 fs/nfsd/debugfs.c |  6 ++++--
 fs/nfsd/nfs4xdr.c |  6 ++++--
 fs/nfsd/vfs.c     | 39 ++++++++++++++++++++++++++++++++++++---
 fs/nfsd/vfs.h     |  2 ++
 4 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/fs/nfsd/debugfs.c b/fs/nfsd/debugfs.c
index 4af1e6b8b212..a10159db3b60 100644
--- a/fs/nfsd/debugfs.c
+++ b/fs/nfsd/debugfs.c
@@ -47,7 +47,8 @@ DEFINE_DEBUGFS_ATTRIBUTE(nfsd_dsr_fops, nfsd_dsr_get, nfsd_dsr_set, "%llu\n");
  *   %2: NFS READ will use direct IO
  *
  * This setting takes immediate effect for all NFS versions,
- * all exports, and in all NFSD net namespaces.
+ * all exports without an explicit riomode= setting, and in all
+ * NFSD net namespaces.
  */
 
 static int nfsd_io_cache_read_get(void *data, u64 *val)
@@ -92,7 +93,8 @@ DEFINE_DEBUGFS_ATTRIBUTE(nfsd_io_cache_read_fops, nfsd_io_cache_read_get,
  *   %1: NFS WRITE will use dontcache (buffered IO w/ dropbehind)
  *
  * This setting takes immediate effect for all NFS versions,
- * all exports, and in all NFSD net namespaces.
+ * all exports without an explicit wiomode= setting, and in all
+ * NFSD net namespaces.
  */
 
 static int nfsd_io_cache_write_get(void *data, u64 *val)
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 4d983444604a..9215feeeb0ba 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -5366,7 +5366,8 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 	maxcount = min_t(unsigned long, read->rd_length,
 			 (xdr->buf->buflen - xdr->buf->len));
 
-	if (file->f_op->splice_read && splice_ok)
+	if (file->f_op->splice_read && splice_ok &&
+	    nfsd_read_iomode(read->rd_fhp->fh_export) == NFSD_IO_BUFFERED)
 		nfserr = nfsd4_encode_splice_read(resp, read, file, maxcount);
 	else
 		nfserr = nfsd4_encode_readv(resp, read, maxcount);
@@ -6264,7 +6265,8 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
 	maxcount = min_t(unsigned long, read->rd_length,
 			 (xdr->buf->buflen - xdr->buf->len));
 
-	if (file->f_op->splice_read && splice_ok)
+	if (file->f_op->splice_read && splice_ok &&
+	    nfsd_read_iomode(read->rd_fhp->fh_export) == NFSD_IO_BUFFERED)
 		nfserr = nfsd4_encode_splice_read(resp, read, file, maxcount);
 	else
 		nfserr = nfsd4_encode_readv(resp, read, maxcount);
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 7f9ec6c4af6d..15613b6df290 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1266,6 +1266,38 @@ static bool nfsd_direct_read_ok(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	return true;
 }
 
+/**
+ * nfsd_read_iomode - effective NFS READ I/O mode for an export
+ * @exp: export being accessed
+ *
+ * An export without an explicit riomode= setting follows the global
+ * nfsd_io_cache_read knob.
+ *
+ * Returns one of NFSD_IO_BUFFERED, NFSD_IO_DONTCACHE, or NFSD_IO_DIRECT.
+ */
+int nfsd_read_iomode(struct svc_export *exp)
+{
+	if (exp->ex_riomode == NFSD_IO_DEFAULT)
+		return nfsd_io_cache_read;
+	return exp->ex_riomode;
+}
+
+/**
+ * nfsd_write_iomode - effective NFS WRITE I/O mode for an export
+ * @exp: export being accessed
+ *
+ * An export without an explicit wiomode= setting follows the global
+ * nfsd_io_cache_write knob.
+ *
+ * Returns one of NFSD_IO_BUFFERED, NFSD_IO_DONTCACHE, or NFSD_IO_DIRECT.
+ */
+int nfsd_write_iomode(struct svc_export *exp)
+{
+	if (exp->ex_wiomode == NFSD_IO_DEFAULT)
+		return nfsd_io_cache_write;
+	return exp->ex_wiomode;
+}
+
 /**
  * nfsd_iter_read - Perform a VFS read using an iterator
  * @rqstp: RPC transaction context
@@ -1300,7 +1332,7 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
 
 	init_sync_kiocb(&kiocb, file);
 
-	switch (nfsd_io_cache_read) {
+	switch (nfsd_read_iomode(fhp->fh_export)) {
 	case NFSD_IO_BUFFERED:
 		break;
 	case NFSD_IO_DIRECT:
@@ -1746,7 +1778,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	if (verf)
 		nfsd_copy_write_verifier(verf, nn);
 
-	switch (nfsd_io_cache_write) {
+	switch (nfsd_write_iomode(exp)) {
 	case NFSD_IO_DIRECT:
 		host_err = nfsd_direct_write(rqstp, fhp, nf, nvecs,
 					     cnt, &kiocb);
@@ -1853,7 +1885,8 @@ __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		return err;
 
 	file = nf->nf_file;
-	if (file->f_op->splice_read && nfsd_read_splice_ok(rqstp))
+	if (file->f_op->splice_read && nfsd_read_splice_ok(rqstp) &&
+	    nfsd_read_iomode(fhp->fh_export) == NFSD_IO_BUFFERED)
 		err = nfsd_splice_read(rqstp, fhp, file, offset, count, eof);
 	else
 		err = nfsd_iter_read(rqstp, fhp, nf, offset, count, eof);
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index 1f05c83a3ea6..e95611b79397 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -184,6 +184,8 @@ __be32		nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
 				struct nfsd_file *nf, loff_t offset,
 				unsigned long *count, u32 *eof);
 bool		nfsd_read_splice_ok(struct svc_rqst *rqstp);
+int		nfsd_read_iomode(struct svc_export *exp);
+int		nfsd_write_iomode(struct svc_export *exp);
 __be32		nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
 				loff_t offset, unsigned long *count,
 				u32 *eof);

-- 
2.56.0