[PATCH v1 0/2] NFSD: Clean ups for recent XDR work

[PATCH v1 0/2] NFSD: Clean ups for recent XDR work

[Chuck Lever]

Hi Bruce-

As we discussed, here are a couple of minor improvements for the
xdr_stream_subsegment() API added when the NFSv4 XDR functions were
recently overhauled. Notably, the second patch changes the NFSv2 and
NFSv3 decoders to work like the NFSv4 one.

---

Chuck Lever (2):
      SUNRPC: xdr_stream_subsegment() must handle non-zero page_bases
      NFSD: Have legacy NFSD WRITE decoders use xdr_stream_subsegment()


 fs/nfsd/nfs3proc.c         |  3 +--
 fs/nfsd/nfs3xdr.c          | 12 ++----------
 fs/nfsd/nfs4proc.c         |  3 +--
 fs/nfsd/nfsproc.c          |  3 +--
 fs/nfsd/nfsxdr.c           |  9 +--------
 fs/nfsd/xdr.h              |  2 +-
 fs/nfsd/xdr3.h             |  2 +-
 include/linux/sunrpc/svc.h |  3 +--
 net/sunrpc/svc.c           | 11 ++++++-----
 net/sunrpc/xdr.c           | 32 +++++++++++++++++---------------
 10 files changed, 32 insertions(+), 48 deletions(-)

--
Chuck Lever

[PATCH v1 1/2] SUNRPC: xdr_stream_subsegment() must handle non-zero page_bases

[Chuck Lever]

xdr_stream_subsegment() was introduced in commit c1346a1216ab
("NFSD: Replace the internals of the READ_BUF() macro").

There are two call sites for xdr_stream_subsegment(). One is
nfsd4_decode_write(), and the other is nfsd4_decode_setxattr().
Currently neither of these call sites calls this API when
xdr_buf::page_base is a non-zero value.

However, I'm about to add a case where page_base will sometimes not
be zero when nfsd4_decode_write() invokes this API. Replace the
logic in xdr_stream_subsegment() that advances to the next data item
in the xdr_stream with something more generic in order to handle
this new use case.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xdr.c |   32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index ca10ba2626f2..df194cc07035 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1633,7 +1633,7 @@ EXPORT_SYMBOL_GPL(xdr_buf_subsegment);
  * Sets up @subbuf to represent a portion of @xdr. The portion
  * starts at the current offset in @xdr, and extends for a length
  * of @nbytes. If this is successful, @xdr is advanced to the next
- * position following that portion.
+ * XDR data item following that portion.
  *
  * Return values:
  *   %true: @subbuf has been initialized, and @xdr has been advanced.
@@ -1642,29 +1642,31 @@ EXPORT_SYMBOL_GPL(xdr_buf_subsegment);
 bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf,
 			   unsigned int nbytes)
 {
-	unsigned int remaining, offset, len;
+	unsigned int start = xdr_stream_pos(xdr);
+	unsigned int remaining, len;
 
-	if (xdr_buf_subsegment(xdr->buf, subbuf, xdr_stream_pos(xdr), nbytes))
+	/* Extract @subbuf and bounds-check the fn arguments */
+	if (xdr_buf_subsegment(xdr->buf, subbuf, start, nbytes))
 		return false;
 
-	if (subbuf->head[0].iov_len)
-		if (!__xdr_inline_decode(xdr, subbuf->head[0].iov_len))
-			return false;
-
-	remaining = subbuf->page_len;
-	offset = subbuf->page_base;
-	while (remaining) {
-		len = min_t(unsigned int, remaining, PAGE_SIZE) - offset;
-
+	/* Advance @xdr by @nbytes */
+	for (remaining = nbytes; remaining;) {
 		if (xdr->p == xdr->end && !xdr_set_next_buffer(xdr))
 			return false;
-		if (!__xdr_inline_decode(xdr, len))
-			return false;
 
+		len = (char *)xdr->end - (char *)xdr->p;
+		if (remaining <= len) {
+			xdr->p = (__be32 *)((char *)xdr->p +
+					(remaining + xdr_pad_size(nbytes)));
+			break;
+		}
+
+		xdr->p = (__be32 *)((char *)xdr->p + len);
+		xdr->end = xdr->p;
 		remaining -= len;
-		offset = 0;
 	}
 
+	xdr_stream_set_pos(xdr, start + nbytes);
 	return true;
 }
 EXPORT_SYMBOL_GPL(xdr_stream_subsegment);

[PATCH v1 2/2] NFSD: Have legacy NFSD WRITE decoders use xdr_stream_subsegment()

[Chuck Lever]

Refactor.

Now that the NFSv2 and NFSv3 XDR decoders have been converted to
use xdr_streams, the WRITE decoder functions can use
xdr_stream_subsegment() to extract the WRITE payload into its own
xdr_buf, just as the NFSv4 WRITE XDR decoder currently does.

That makes it possible to pass the first kvec, pages array + length,
page_base, and total payload length via a single function parameter.

The payload's page_base is not yet assigned or used, but will be in
subsequent patches.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfs3proc.c         |    3 +--
 fs/nfsd/nfs3xdr.c          |   12 ++----------
 fs/nfsd/nfs4proc.c         |    3 +--
 fs/nfsd/nfsproc.c          |    3 +--
 fs/nfsd/nfsxdr.c           |    9 +--------
 fs/nfsd/xdr.h              |    2 +-
 fs/nfsd/xdr3.h             |    2 +-
 include/linux/sunrpc/svc.h |    3 +--
 net/sunrpc/svc.c           |   11 ++++++-----
 9 files changed, 15 insertions(+), 33 deletions(-)

diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 17715a6c7a40..4418517f6f12 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -201,8 +201,7 @@ nfsd3_proc_write(struct svc_rqst *rqstp)
 
 	fh_copy(&resp->fh, &argp->fh);
 	resp->committed = argp->stable;
-	nvecs = svc_fill_write_vector(rqstp, rqstp->rq_arg.pages,
-				      &argp->first, cnt);
+	nvecs = svc_fill_write_vector(rqstp, &argp->payload);
 	if (!nvecs) {
 		resp->status = nfserr_io;
 		goto out;
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 0a5ebc52e6a9..91d4e2b8b854 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -621,9 +621,6 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p)
 	struct xdr_stream *xdr = &rqstp->rq_arg_stream;
 	struct nfsd3_writeargs *args = rqstp->rq_argp;
 	u32 max_blocksize = svc_max_payload(rqstp);
-	struct kvec *head = rqstp->rq_arg.head;
-	struct kvec *tail = rqstp->rq_arg.tail;
-	size_t remaining;
 
 	if (!svcxdr_decode_nfs_fh3(xdr, &args->fh))
 		return 0;
@@ -641,17 +638,12 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p)
 	/* request sanity */
 	if (args->count != args->len)
 		return 0;
-	remaining = head->iov_len + rqstp->rq_arg.page_len + tail->iov_len;
-	remaining -= xdr_stream_pos(xdr);
-	if (remaining < xdr_align_size(args->len))
-		return 0;
 	if (args->count > max_blocksize) {
 		args->count = max_blocksize;
 		args->len = max_blocksize;
 	}
-
-	args->first.iov_base = xdr->p;
-	args->first.iov_len = head->iov_len - xdr_stream_pos(xdr);
+	if (!xdr_stream_subsegment(xdr, &args->payload, args->count))
+		return 0;
 
 	return 1;
 }
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 486c5dba4b65..55c9551fa74e 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1033,8 +1033,7 @@ nfsd4_write(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 
 	write->wr_how_written = write->wr_stable_how;
 
-	nvecs = svc_fill_write_vector(rqstp, write->wr_payload.pages,
-				      write->wr_payload.head, write->wr_buflen);
+	nvecs = svc_fill_write_vector(rqstp, &write->wr_payload);
 	WARN_ON_ONCE(nvecs > ARRAY_SIZE(rqstp->rq_vec));
 
 	status = nfsd_vfs_write(rqstp, &cstate->current_fh, nf,
diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index 90fcd6178823..eea5b59b6a6c 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -234,8 +234,7 @@ nfsd_proc_write(struct svc_rqst *rqstp)
 		SVCFH_fmt(&argp->fh),
 		argp->len, argp->offset);
 
-	nvecs = svc_fill_write_vector(rqstp, rqstp->rq_arg.pages,
-				      &argp->first, cnt);
+	nvecs = svc_fill_write_vector(rqstp, &argp->payload);
 	if (!nvecs) {
 		resp->status = nfserr_io;
 		goto out;
diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
index a06c05fe3b42..26a42f87c240 100644
--- a/fs/nfsd/nfsxdr.c
+++ b/fs/nfsd/nfsxdr.c
@@ -325,10 +325,7 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p)
 {
 	struct xdr_stream *xdr = &rqstp->rq_arg_stream;
 	struct nfsd_writeargs *args = rqstp->rq_argp;
-	struct kvec *head = rqstp->rq_arg.head;
-	struct kvec *tail = rqstp->rq_arg.tail;
 	u32 beginoffset, totalcount;
-	size_t remaining;
 
 	if (!svcxdr_decode_fhandle(xdr, &args->fh))
 		return 0;
@@ -346,12 +343,8 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p)
 		return 0;
 	if (args->len > NFSSVC_MAXBLKSIZE_V2)
 		return 0;
-	remaining = head->iov_len + rqstp->rq_arg.page_len + tail->iov_len;
-	remaining -= xdr_stream_pos(xdr);
-	if (remaining < xdr_align_size(args->len))
+	if (!xdr_stream_subsegment(xdr, &args->payload, args->len))
 		return 0;
-	args->first.iov_base = xdr->p;
-	args->first.iov_len = head->iov_len - xdr_stream_pos(xdr);
 
 	return 1;
 }
diff --git a/fs/nfsd/xdr.h b/fs/nfsd/xdr.h
index f45b4bc93f52..80fd6d7f3404 100644
--- a/fs/nfsd/xdr.h
+++ b/fs/nfsd/xdr.h
@@ -33,7 +33,7 @@ struct nfsd_writeargs {
 	svc_fh			fh;
 	__u32			offset;
 	int			len;
-	struct kvec		first;
+	struct xdr_buf		payload;
 };
 
 struct nfsd_createargs {
diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h
index 933008382bbe..712c117300cb 100644
--- a/fs/nfsd/xdr3.h
+++ b/fs/nfsd/xdr3.h
@@ -40,7 +40,7 @@ struct nfsd3_writeargs {
 	__u32			count;
 	int			stable;
 	__u32			len;
-	struct kvec		first;
+	struct xdr_buf		payload;
 };
 
 struct nfsd3_createargs {
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 064c96157d1f..6263410c948a 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -532,8 +532,7 @@ int		   svc_encode_result_payload(struct svc_rqst *rqstp,
 					     unsigned int offset,
 					     unsigned int length);
 unsigned int	   svc_fill_write_vector(struct svc_rqst *rqstp,
-					 struct page **pages,
-					 struct kvec *first, size_t total);
+					 struct xdr_buf *payload);
 char		  *svc_fill_symlink_pathname(struct svc_rqst *rqstp,
 					     struct kvec *first, void *p,
 					     size_t total);
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index a3bbe5ce4570..08ca797bb8a4 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1676,16 +1676,17 @@ EXPORT_SYMBOL_GPL(svc_encode_result_payload);
 /**
  * svc_fill_write_vector - Construct data argument for VFS write call
  * @rqstp: svc_rqst to operate on
- * @pages: list of pages containing data payload
- * @first: buffer containing first section of write payload
- * @total: total number of bytes of write payload
+ * @payload: xdr_buf containing only the write data payload
  *
  * Fills in rqstp::rq_vec, and returns the number of elements.
  */
-unsigned int svc_fill_write_vector(struct svc_rqst *rqstp, struct page **pages,
-				   struct kvec *first, size_t total)
+unsigned int svc_fill_write_vector(struct svc_rqst *rqstp,
+				   struct xdr_buf *payload)
 {
+	struct page **pages = payload->pages;
+	struct kvec *first = payload->head;
 	struct kvec *vec = rqstp->rq_vec;
+	size_t total = payload->len;
 	unsigned int i;
 
 	/* Some types of transport can present the write payload

Re: [PATCH v1 0/2] NFSD: Clean ups for recent XDR work

[J. Bruce Fields]

On Thu, Sep 30, 2021 at 05:06:09PM -0400, Chuck Lever wrote:
> As we discussed, here are a couple of minor improvements for the
> xdr_stream_subsegment() API added when the NFSv4 XDR functions were
> recently overhauled. Notably, the second patch changes the NFSv2 and
> NFSv3 decoders to work like the NFSv4 one.

Looks good to me; applying.

--b.

> 
> ---
> 
> Chuck Lever (2):
>       SUNRPC: xdr_stream_subsegment() must handle non-zero page_bases
>       NFSD: Have legacy NFSD WRITE decoders use xdr_stream_subsegment()
> 
> 
>  fs/nfsd/nfs3proc.c         |  3 +--
>  fs/nfsd/nfs3xdr.c          | 12 ++----------
>  fs/nfsd/nfs4proc.c         |  3 +--
>  fs/nfsd/nfsproc.c          |  3 +--
>  fs/nfsd/nfsxdr.c           |  9 +--------
>  fs/nfsd/xdr.h              |  2 +-
>  fs/nfsd/xdr3.h             |  2 +-
>  include/linux/sunrpc/svc.h |  3 +--
>  net/sunrpc/svc.c           | 11 ++++++-----
>  net/sunrpc/xdr.c           | 32 +++++++++++++++++---------------
>  10 files changed, 32 insertions(+), 48 deletions(-)
> 
> --
> Chuck Lever