[PATCH v2 5/6] nfs4.2: request UNCACHEABLE_DIRENT_METADATA only for directories

[Mike Snitzer <snitzer@kernel.org>]

The UNCACHEABLE_DIRENT_METADATA attribute (attr 88) applies only to
directory objects (NF4DIR); per draft-ietf-nfsv4-uncacheable-directories
a server must reject a query of it on any other object type with
NFS4ERR_INVAL.  Gate the request by object type at the single choke point
nfs4_bitmap_copy_adjust(), stripping FATTR4_WORD2_UNCACHEABLE_DIRENT_METADATA
unless the target is known to be a directory (callers with an unknown
object type, e.g. LOOKUP/LOOKUPP/CREATE, pass a NULL inode and are already
routed through this helper).  This mirrors the NF4REG gating of the
companion UNCACHEABLE_FILE_DATA attribute: a regular file requests
file_data and never dirent_metadata, a directory requests dirent_metadata
and never file_data, and an unknown/other object requests neither.

The bit stays in server->attr_bitmask, so OPEN (which requests the
regular-file open bitmap) is unaffected.  This type gate runs before the
helper's read/write (file) delegation handling and is the only adjustment
the directory attribute needs: a directory cannot hold a file delegation,
so the delegation-based suppression below it never applies.

See: https://datatracker.ietf.org/doc/draft-ietf-nfsv4-uncacheable-directories/

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Assisted-by: Claude:claude-opus-4-8
---
 fs/nfs/nfs4proc.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index d912f6a43978..a4c40e12d621 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -312,13 +312,16 @@ static void nfs4_bitmap_copy_adjust(__u32 *dst, const __u32 *src,
 	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).
+	 * (NF4REG) and the uncacheable_dirent_metadata attribute only to
+	 * directories (NF4DIR); a server must reject a query of either on any
+	 * other object type with NFS4ERR_INVAL.  Never request either unless
+	 * the target is known to be of the matching type (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 || !S_ISDIR(inode->i_mode))
+		dst[2] &= ~FATTR4_WORD2_UNCACHEABLE_DIRENT_METADATA;
 	if (!inode || !nfs_have_read_or_write_delegation(inode))
 		return;
 
-- 
2.47.3