[PATCH v3 00/34] Convert server-side NFSv3 XDR to use xdrgen

[PATCH v3 00/34] Convert server-side NFSv3 XDR to use xdrgen

[Chuck Lever]

Replace NFSD's NFSv3 XDR encoders and decoders with code that is
mechanically generated directly from the NFSv3 RPC language
specification. Unlike NFSv2, where there are at least two
incomplete language specifications and much lore, nfs3.x here is
based closely on RFC 1813.

As we convert newer NFS versions to use xdrgen, I expect a reduction
in human coding errors, improved spec compliance, quicker implement-
ation of new protocol, and better memory safety for the more complex
NFS procedures.

Changes in v3:
- Copy the SYMLINK target with nfsd_symlink_target(), moved into vfs.c.
- Add a patch removing the now-unused svc_fill_symlink_pathname().
- Reject a READDIRPLUS entry on its minimum size before the lookup.
- Drop the pr_warn_once() for an unexpected file type in GETATTR.
- Explain why a late readdir host error is not reported as the status.
- Write "committed", not "on the wire", in the first-batch patch.
- Link to v2: https://lore.kernel.org/linux-nfs/20260924171012.3978-1-cel@kernel.org/

Changes in v2:
- Include the generated NFSv3 header directly in nfsfh.c and nfsctl.c.
- Remove the unused struct nfsd3_createargs in the MKDIR patch.
- Regenerate the READDIR and READDIRPLUS result decoders.
- Drop the decode-hook stubs the regenerated decoders no longer call.
- Link to v1: https://lore.kernel.org/linux-nfs/20260923132811.244160-1-cel@kernel.org/

Chuck Lever (34):
  NFSD: Report a first-batch readdir error in the reply status
  Documentation: Add the RPC language description of NFSv3
  NFSD: Add infrastructure for generating NFSv3 XDR encoders and
    decoders
  NFSD: Replace nfs3.h with nfs3xdr_gen.h
  NFSD: Replace the nfsd3_createres macro
  NFSD: Relocate the NFSv3 XDR storage union into nfs3proc.c
  NFSD: Use xdrgen XDR functions for the NFSv3 NULL procedure
  NFSD: Use xdrgen XDR functions for NFSv3 GETATTR procedure
  NFSD: Use xdrgen XDR functions for NFSv3 SETATTR procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 LOOKUP procedure
  NFSD: Use xdrgen XDR functions for NFSv3 ACCESS procedure
  NFSD: Use xdrgen XDR functions for NFSv3 READLINK procedure
  NFSD: Use xdrgen XDR functions for NFSv3 READ procedure
  NFSD: Use xdrgen XDR functions for NFSv3 WRITE procedure
  NFSD: Use xdrgen XDR functions for NFSv3 CREATE procedure
  NFSD: Use xdrgen XDR functions for NFSv3 MKDIR procedure
  NFSD: Use xdrgen XDR functions for NFSv3 SYMLINK procedure
  NFSD: Use xdrgen XDR functions for NFSv3 MKNOD procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 REMOVE procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 RMDIR procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 RENAME procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 LINK procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 FSSTAT procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 FSINFO procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 PATHCONF procedure
  NFSD: Use xdrgen XDR functions for the NFSv3 COMMIT procedure
  NFSD: Use xdrgen XDR functions for NFSv3 READDIR arguments
  NFSD: Use xdrgen XDR functions for NFSv3 READDIRPLUS arguments
  NFSD: Refactor NFSv3 directory cookie encoding
  NFSD: Refactor NFSv3 directory entry encoding
  NFSD: Split struct nfsd3_readdirres
  NFSD: Use xdrgen XDR functions for NFSv3 READDIR results
  NFSD: Use xdrgen XDR functions for NFSv3 READDIRPLUS results
  SUNRPC: Remove svc_fill_symlink_pathname()

 Documentation/sunrpc/xdr/nfs3.x    |  839 ++++++
 fs/nfsd/Makefile                   |   15 +-
 fs/nfsd/nfs2acl.c                  |   41 +-
 fs/nfsd/nfs3acl.c                  |   12 +-
 fs/nfsd/nfs3proc.c                 | 2541 +++++++++++++------
 fs/nfsd/nfs3xdr.c                  | 1374 +++-------
 fs/nfsd/nfs3xdr_gen.c              | 3808 ++++++++++++++++++++++++++++
 fs/nfsd/nfs3xdr_gen.h              |   82 +
 fs/nfsd/nfsctl.c                   |    2 +-
 fs/nfsd/nfserr.h                   |    2 +-
 fs/nfsd/nfsfh.c                    |    2 +-
 fs/nfsd/nfsproc.c                  |   22 -
 fs/nfsd/vfs.c                      |  105 +-
 fs/nfsd/vfs.h                      |    1 +
 fs/nfsd/xdr3.h                     |  300 +--
 include/linux/nfs3.h               |    3 -
 include/linux/sunrpc/svc.h         |    3 -
 include/linux/sunrpc/xdrgen/nfs3.h | 1092 ++++++++
 net/sunrpc/svc.c                   |   50 -
 19 files changed, 8052 insertions(+), 2242 deletions(-)
 create mode 100644 Documentation/sunrpc/xdr/nfs3.x
 create mode 100644 fs/nfsd/nfs3xdr_gen.c
 create mode 100644 fs/nfsd/nfs3xdr_gen.h
 create mode 100644 include/linux/sunrpc/xdrgen/nfs3.h

-- 
2.55.0

[PATCH v3 01/34] NFSD: Report a first-batch readdir error in the reply status

[Chuck Lever]

The NFSv2 READDIR encoder pulls directory entries while the reply
is encoded, after the status word is committed. nfsd_readdir_open()
does not read from the directory, so an iterate_dir() failure on the
first batch surfaces only in nfsd_readdir_next(), where nothing can
turn it into a status. The reply carries NFS_OK, no entries, and eof
false. The client resends the same cookie and receives the same reply,
so a directory that fails with -EIO or -ENOENT traps it in a loop.

Read the first batch in nfsd_readdir_open() so the error selects the
reply status before any of it is committed. An error on a later batch
still cuts the list short with eof false. The client's follow-up
request then starts from that cookie and gets the error in its status.

Signed-off-by: Chuck Lever <cel@kernel.org>
---
 fs/nfsd/vfs.c | 76 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 50 insertions(+), 26 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index c7dd94697f2f..c753d3257f1e 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -2397,6 +2397,33 @@ static bool nfsd_buffered_filldir(struct dir_context *ctx, const char *name,
 	return true;
 }
 
+/*
+ * Read the next batch of entries.  Returns false at end of directory
+ * (@iter->eof set) or on a filesystem error (@iter->host_err set).
+ */
+static bool nfsd_readdir_fill(struct nfsd_readdir_iter *iter)
+{
+	/* Between batches the resume cookie advances past the last. */
+	if (iter->batched)
+		iter->offset = vfs_llseek(iter->file, 0, SEEK_CUR);
+
+	iter->used = 0;
+	iter->full = 0;
+	iter->host_err = iterate_dir(iter->file, &iter->ctx);
+	if (iter->full)
+		iter->host_err = 0;
+	if (iter->host_err < 0)
+		return false;
+	if (!iter->used) {
+		iter->eof = true;
+		return false;
+	}
+	iter->batched = true;
+	iter->pos = iter->page;
+	iter->remaining = iter->used;
+	return true;
+}
+
 /**
  * nfsd_readdir_open - open a directory for streaming readdir
  * @rqstp: RPC transaction context
@@ -2404,13 +2431,15 @@ static bool nfsd_buffered_filldir(struct dir_context *ctx, const char *name,
  * @offsetp: seek offset at which to resume reading
  * @iter: OUT: directory reader to initialize
  *
- * On success the directory is open and positioned at @offsetp, and
- * @iter is ready for nfsd_readdir_next().  The caller must release
- * @iter with nfsd_readdir_close() once done, including on error paths
- * that follow a successful open.
+ * On success the directory is open and positioned at @offsetp, the
+ * first batch of entries has been read, and @iter is ready for
+ * nfsd_readdir_next().  The caller must release @iter with
+ * nfsd_readdir_close() once done, including on error paths that
+ * follow a successful open.
  *
- * Return: nfs_ok on success, otherwise an nfsstat code.  On error @iter
- * is left safe to pass to nfsd_readdir_close().
+ * Return: nfs_ok on success, otherwise an nfsstat code, including the
+ * error from reading the first batch.  On error @iter is left safe to
+ * pass to nfsd_readdir_close().
  */
 __be32 nfsd_readdir_open(struct svc_rqst *rqstp, struct svc_fh *fhp,
 			 loff_t *offsetp, struct nfsd_readdir_iter *iter)
@@ -2446,6 +2475,17 @@ __be32 nfsd_readdir_open(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	iter->file = file;
 	iter->fhp = fhp;
 	iter->offset = offset;
+
+	/*
+	 * The first batch is read here so a filesystem error surfaces
+	 * in the reply status.  Once the encoder has committed nfs_ok,
+	 * an error can only be reported as a short list.
+	 */
+	if (!nfsd_readdir_fill(iter) && iter->host_err) {
+		err = nfserrno(iter->host_err);
+		nfsd_readdir_close(iter);
+		return err;
+	}
 	return nfs_ok;
 
 out_close:
@@ -2470,26 +2510,10 @@ struct buffered_dirent *nfsd_readdir_next(struct nfsd_readdir_iter *iter)
 	struct buffered_dirent *de;
 	unsigned int reclen;
 
-	while (iter->remaining <= 0) {
-		/* Between batches the resume cookie advances past the last. */
-		if (iter->batched)
-			iter->offset = vfs_llseek(iter->file, 0, SEEK_CUR);
-
-		iter->used = 0;
-		iter->full = 0;
-		iter->host_err = iterate_dir(iter->file, &iter->ctx);
-		if (iter->full)
-			iter->host_err = 0;
-		if (iter->host_err < 0)
-			return NULL;
-		if (!iter->used) {
-			iter->eof = true;
-			return NULL;
-		}
-		iter->batched = true;
-		iter->pos = iter->page;
-		iter->remaining = iter->used;
-	}
+	if (iter->eof || iter->host_err)
+		return NULL;
+	if (iter->remaining <= 0 && !nfsd_readdir_fill(iter))
+		return NULL;
 
 	de = (struct buffered_dirent *)iter->pos;
 	iter->offset = de->offset;
-- 
2.55.0