[PATCH v13 14/15] nfsd: Implement NFSv4 FATTR4_CASE_INSENSITIVE and FATTR4_CASE_PRESERVING
From: Chuck Lever <cel@kernel.org>
Date: 2026-05-02 14:22:36
Also in:
linux-cifs, linux-ext4, linux-f2fs-devel, linux-fsdevel, linux-nfs, linux-xfs
Subsystem:
filesystems (vfs and infrastructure), kernel nfsd, sunrpc, and lockd servers, the rest · Maintainers:
Alexander Viro, Christian Brauner, Chuck Lever, Jeff Layton, Linus Torvalds
From: Chuck Lever <chuck.lever@oracle.com> NFSD currently provides NFSv4 clients with hard-coded responses indicating all exported filesystems are case-sensitive and case-preserving. This is incorrect for case-insensitive filesystems and ext4 directories with casefold enabled. Query the underlying filesystem's actual case sensitivity via nfsd_get_case_info() and return accurate values to clients. This supports per-directory settings for filesystems that allow mixing case-sensitive and case-insensitive directories within an export. The helper queries the parent dentry for non-directory filehandles because case-folding is a per-directory property. That resolution has the same corner cases here as for NFSv3 PATHCONF: single-file exports query an unexported parent, disconnected dentries report defaults until reconnected, and hardlinked files track whichever alias the dcache currently holds. Reviewed-by: Roland Mainz <redacted> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> --- fs/nfsd/nfs4xdr.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 49 insertions(+), 3 deletions(-)
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 2a0946c630e1..d77304692e11 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c@@ -3158,6 +3158,8 @@ struct nfsd4_fattr_args { u32 rdattr_err; bool contextsupport; bool ignore_crossmnt; + bool case_insensitive; + bool case_preserving; }; typedef __be32(*nfsd4_enc_attr)(struct xdr_stream *xdr,
@@ -3356,6 +3358,33 @@ static __be32 nfsd4_encode_fattr4_acl(struct xdr_stream *xdr, return nfs_ok; } +static __be32 nfsd4_encode_fattr4_case_insensitive(struct xdr_stream *xdr, + const struct nfsd4_fattr_args *args) +{ + return nfsd4_encode_bool(xdr, args->case_insensitive); +} + +static __be32 nfsd4_encode_fattr4_case_preserving(struct xdr_stream *xdr, + const struct nfsd4_fattr_args *args) +{ + return nfsd4_encode_bool(xdr, args->case_preserving); +} + +static __be32 nfsd4_encode_fattr4_homogeneous(struct xdr_stream *xdr, + const struct nfsd4_fattr_args *args) +{ + /* + * Casefold-capable filesystems (e.g. ext4 or f2fs with the + * casefold feature) attach a Unicode encoding at mount time + * but apply case folding per directory. The per-file-system + * case_insensitive and case_preserving values can therefore + * legitimately differ across objects that share the same fsid. + * Report FATTR4_HOMOGENEOUS = FALSE on such filesystems to + * keep that variation consistent with RFC 8881 Section 5.8.2.16. + */ + return nfsd4_encode_bool(xdr, !sb_has_encoding(args->dentry->d_sb)); +} + static __be32 nfsd4_encode_fattr4_filehandle(struct xdr_stream *xdr, const struct nfsd4_fattr_args *args) {
@@ -3748,8 +3777,8 @@ static const nfsd4_enc_attr nfsd4_enc_fattr4_encode_ops[] = { [FATTR4_ACLSUPPORT] = nfsd4_encode_fattr4_aclsupport, [FATTR4_ARCHIVE] = nfsd4_encode_fattr4__noop, [FATTR4_CANSETTIME] = nfsd4_encode_fattr4__true, - [FATTR4_CASE_INSENSITIVE] = nfsd4_encode_fattr4__false, - [FATTR4_CASE_PRESERVING] = nfsd4_encode_fattr4__true, + [FATTR4_CASE_INSENSITIVE] = nfsd4_encode_fattr4_case_insensitive, + [FATTR4_CASE_PRESERVING] = nfsd4_encode_fattr4_case_preserving, [FATTR4_CHOWN_RESTRICTED] = nfsd4_encode_fattr4__true, [FATTR4_FILEHANDLE] = nfsd4_encode_fattr4_filehandle, [FATTR4_FILEID] = nfsd4_encode_fattr4_fileid,
@@ -3758,7 +3787,7 @@ static const nfsd4_enc_attr nfsd4_enc_fattr4_encode_ops[] = { [FATTR4_FILES_TOTAL] = nfsd4_encode_fattr4_files_total, [FATTR4_FS_LOCATIONS] = nfsd4_encode_fattr4_fs_locations, [FATTR4_HIDDEN] = nfsd4_encode_fattr4__noop, - [FATTR4_HOMOGENEOUS] = nfsd4_encode_fattr4__true, + [FATTR4_HOMOGENEOUS] = nfsd4_encode_fattr4_homogeneous, [FATTR4_MAXFILESIZE] = nfsd4_encode_fattr4_maxfilesize, [FATTR4_MAXLINK] = nfsd4_encode_fattr4_maxlink, [FATTR4_MAXNAME] = nfsd4_encode_fattr4_maxname,
@@ -3968,6 +3997,23 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr, args.fhp = tempfh; } else args.fhp = fhp; + if (attrmask[0] & (FATTR4_WORD0_CASE_INSENSITIVE | + FATTR4_WORD0_CASE_PRESERVING)) { + err = nfsd_get_case_info(dentry, &args.case_insensitive, + &args.case_preserving); + /* + * SUPPORTED_ATTRS unconditionally advertises both + * bits, and the Linux client treats an absent + * CASE_PRESERVING in a GETATTR reply as false. When + * the filesystem does not expose case state, + * nfsd_get_case_info() fills POSIX defaults + * (case-sensitive, case-preserving) and returns + * -EOPNOTSUPP; encode those defaults so the reply + * agrees with what the server claims to support. + */ + if (err && err != -EOPNOTSUPP) + goto out_nfserr; + } if (attrmask[0] & FATTR4_WORD0_ACL) { err = nfsd4_get_nfs4_acl(rqstp, dentry, &args.acl);
--
2.53.0