[PATCH 3/4] nfs4.2: request UNCACHEABLE_FILE_DATA only for regular files

[Mike Snitzer <snitzer@kernel.org>]

The UNCACHEABLE_FILE_DATA attribute applies only to regular files
(NF4REG); per draft-ietf-nfsv4-uncacheable-files a server MUST reject a
query of it on any other object type with NFS4ERR_INVAL.  The previous
commit decodes and tracks the attribute but does not gate it: the bit
rides in the per-server attribute bitmask (server->attr_bitmask) and in
the generic getattr request bitmap (nfs4_fattr_bitmap), so it would be
requested for non-regular objects too -- e.g. a plain directory GETATTR,
a LOOKUP that resolves to a directory, or a CREATE (which only ever makes
non-regular objects).  A strict server would fail those compounds.

Gate the client accordingly:

 - Only set NFS_INO_INVALID_UNCACHEABLE_FILE_DATA on regular-file inodes,
   so the attribute is never (re)requested for directories or other
   non-regular objects via the delegation GETATTR or nfs4_bitmask_set()
   refresh paths.

 - Gate the request by object type at the single choke point
   nfs4_bitmap_copy_adjust(), which clears
   FATTR4_WORD2_UNCACHEABLE_FILE_DATA unless the target inode is a
   regular file (a NULL inode -- unknown object type -- clears it too).
   This already covers GETATTR, SETATTR and LINK; route LOOKUP, LOOKUPP
   and CREATE through it as well.

The bit is kept in server->attr_bitmask (it is server-supported, and OPEN
still requests it via its regular-file-only open_bitmap), so no bespoke
per-data-file bitmask plumbing is needed.  The remaining getattr-bearing
compounds are already safe: ACCESS, DELEGRETURN, WRITE, CLOSE and
LAYOUTCOMMIT use server->cache_consistency_bitmask (no word2 attributes)
or operate on regular files; READDIR does not encode the bit; and
LOOKUP_ROOT, FSINFO, STATFS and PATHCONF use fixed bitmaps without it.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Assisted-by: Claude:claude-opus-4-8
---
 fs/nfs/inode.c    |  6 ++++--
 fs/nfs/nfs4proc.c | 37 ++++++++++++++++++++++++++++++++++---
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index c1227b7c5545..edadc3142592 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -565,7 +565,8 @@ nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
 		if (fattr->valid & NFS_ATTR_FATTR_UNCACHEABLE_FILE_DATA)
 			nfsi->uncacheable_file_data =
 				!!(fattr->aux_flags & NFS_AUX_UNCACHEABLE_FILE_DATA);
-		else if (fattr_supported & NFS_ATTR_FATTR_UNCACHEABLE_FILE_DATA)
+		else if (S_ISREG(inode->i_mode) &&
+			 (fattr_supported & NFS_ATTR_FATTR_UNCACHEABLE_FILE_DATA))
 			nfs_set_cache_invalid(inode, NFS_INO_INVALID_UNCACHEABLE_FILE_DATA);
 
 		nfs_setsecurity(inode, fattr);
@@ -2473,7 +2474,8 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 	if (fattr->valid & NFS_ATTR_FATTR_UNCACHEABLE_FILE_DATA)
 		nfsi->uncacheable_file_data =
 				!!(fattr->aux_flags & NFS_AUX_UNCACHEABLE_FILE_DATA);
-	else if (fattr_supported & NFS_ATTR_FATTR_UNCACHEABLE_FILE_DATA)
+	else if (S_ISREG(inode->i_mode) &&
+		 (fattr_supported & NFS_ATTR_FATTR_UNCACHEABLE_FILE_DATA))
 		nfsi->cache_validity |=
 			save_cache_validity & NFS_INO_INVALID_UNCACHEABLE_FILE_DATA;
 
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index d237abca4793..72d809463de7 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -308,6 +308,15 @@ static void nfs4_bitmap_copy_adjust(__u32 *dst, const __u32 *src,
 	unsigned long cache_validity;
 
 	memcpy(dst, src, NFS4_BITMASK_SZ*sizeof(*dst));
+	/*
+	 * The uncacheable_file_data attribute applies only to regular files
+	 * (NF4REG); a server must reject a query of it on any other object
+	 * type with NFS4ERR_INVAL.  Never request it unless the target is
+	 * known to be a regular file (callers with an unknown object type,
+	 * e.g. LOOKUP, pass a NULL inode).
+	 */
+	if (!inode || !S_ISREG(inode->i_mode))
+		dst[2] &= ~FATTR4_WORD2_UNCACHEABLE_FILE_DATA;
 	if (!inode || !nfs_have_read_or_write_delegation(inode))
 		return;
 
@@ -4599,6 +4608,7 @@ static int _nfs4_proc_lookup(struct rpc_clnt *clnt, struct inode *dir,
 		.rpc_resp = &res,
 	};
 	unsigned short task_flags = 0;
+	__u32 bitmask[NFS4_BITMASK_SZ];
 
 	if (nfs_server_capable(dir, NFS_CAP_MOVEABLE))
 		task_flags = RPC_TASK_MOVEABLE;
@@ -4607,7 +4617,13 @@ static int _nfs4_proc_lookup(struct rpc_clnt *clnt, struct inode *dir,
 	if (nfs_lookup_is_soft_revalidate(dentry))
 		task_flags |= RPC_TASK_TIMEOUT;
 
-	args.bitmask = nfs4_bitmask(server, fattr->label);
+	/*
+	 * The looked-up object's type is unknown here, so gate out the
+	 * regular-file-only uncacheable_file_data attribute (NULL inode).
+	 */
+	nfs4_bitmap_copy_adjust(bitmask, nfs4_bitmask(server, fattr->label),
+				NULL, 0);
+	args.bitmask = bitmask;
 
 	nfs_fattr_init(fattr);
 
@@ -4721,13 +4737,20 @@ static int _nfs4_proc_lookupp(struct inode *inode,
 		.rpc_resp = &res,
 	};
 	unsigned short task_flags = 0;
+	__u32 bitmask[NFS4_BITMASK_SZ];
 
 	if (server->flags & NFS_MOUNT_SOFTREVAL)
 		task_flags |= RPC_TASK_TIMEOUT;
 	if (server->caps & NFS_CAP_MOVEABLE)
 		task_flags |= RPC_TASK_MOVEABLE;
 
-	args.bitmask = nfs4_bitmask(server, fattr->label);
+	/*
+	 * The looked-up object's type is unknown here, so gate out the
+	 * regular-file-only uncacheable_file_data attribute (NULL inode).
+	 */
+	nfs4_bitmap_copy_adjust(bitmask, nfs4_bitmask(server, fattr->label),
+				NULL, 0);
+	args.bitmask = bitmask;
 
 	nfs_fattr_init(fattr);
 	nfs4_init_sequence(server->nfs_client, &args.seq_args, &res.seq_res, 0, 0);
@@ -5142,6 +5165,7 @@ struct nfs4_createdata {
 	struct nfs4_create_res res;
 	struct nfs_fh fh;
 	struct nfs_fattr fattr;
+	u32 bitmask[NFS4_BITMASK_SZ];
 };
 
 static struct nfs4_createdata *nfs4_alloc_createdata(struct inode *dir,
@@ -5165,7 +5189,14 @@ static struct nfs4_createdata *nfs4_alloc_createdata(struct inode *dir,
 		data->arg.name = name;
 		data->arg.attrs = sattr;
 		data->arg.ftype = ftype;
-		data->arg.bitmask = nfs4_bitmask(server, data->fattr.label);
+		/*
+		 * CREATE only makes non-regular objects, so gate out the
+		 * regular-file-only uncacheable_file_data attribute (NULL inode).
+		 */
+		nfs4_bitmap_copy_adjust(data->bitmask,
+					nfs4_bitmask(server, data->fattr.label),
+					NULL, 0);
+		data->arg.bitmask = data->bitmask;
 		data->arg.umask = current_umask();
 		data->res.server = server;
 		data->res.fh = &data->fh;
-- 
2.47.3