Re: [PATCH] NFSD: Replace isdotent() macro

On Sun, 2026-06-21 at 17:35 -0400, Chuck Lever wrote:
> The VFS provides name_is_dot_dotdot() as the canonical helper for
> recognizing the "." and ".." directory entries, and fs/ already uses
> it widely. nfsd has instead carried its own open-coded isdotent()
> macro that computes the same predicate for non-empty names, a needless
> duplicate of shared functionality. The macro reads the first name byte
> without first confirming the name is non-empty; name_is_dot_dotdot()
> tests the length first, so it never touches a zero-length buffer.
> Convert every isdotent() call site to the generic helper and remove the
> macro.
> 
> Signed-off-by: Chuck Lever <[email protected]>
> ---
>  fs/nfsd/nfs3proc.c |  2 +-
>  fs/nfsd/nfs3xdr.c  |  2 +-
>  fs/nfsd/nfs4proc.c |  2 +-
>  fs/nfsd/nfs4xdr.c  |  4 ++--
>  fs/nfsd/nfsd.h     |  3 ---
>  fs/nfsd/nfsproc.c  |  2 +-
>  fs/nfsd/vfs.c      | 13 +++++++------
>  7 files changed, 13 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
> index 42adc5461db0..a14827cfeeb8 100644
> --- a/fs/nfsd/nfs3proc.c
> +++ b/fs/nfsd/nfs3proc.c
> @@ -265,7 +265,7 @@ nfsd3_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  
>  	trace_nfsd_vfs_create(rqstp, fhp, S_IFREG, argp->name, argp->len);
>  
> -	if (isdotent(argp->name, argp->len))
> +	if (name_is_dot_dotdot(argp->name, argp->len))
>  		return nfserr_exist;
>  	if (!(iap->ia_valid & ATTR_MODE))
>  		iap->ia_mode = 0;
> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> index 2ff9a991a8fb..e481804bb120 100644
> --- a/fs/nfsd/nfs3xdr.c
> +++ b/fs/nfsd/nfs3xdr.c
> @@ -987,7 +987,7 @@ compose_entry_fh(struct nfsd3_readdirres *cd, struct svc_fh *fhp,
>  	dparent = cd->fh.fh_dentry;
>  	exp  = cd->fh.fh_export;
>  
> -	if (isdotent(name, namlen)) {
> +	if (name_is_dot_dotdot(name, namlen)) {
>  		if (namlen == 2) {
>  			dchild = dget_parent(dparent);
>  			/*
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 907b899a90da..654705d1dd37 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -259,7 +259,7 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  	__be32 status;
>  	int host_err;
>  
> -	if (isdotent(open->op_fname, open->op_fnamelen))
> +	if (name_is_dot_dotdot(open->op_fname, open->op_fnamelen))
>  		return nfserr_exist;
>  	if (!(iap->ia_valid & ATTR_MODE))
>  		iap->ia_mode = 0;
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 2a0946c630e1..8db16a30d971 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -98,7 +98,7 @@ check_filename(char *str, int len)
>  		return nfserr_inval;
>  	if (len > NFS4_MAXNAMLEN)
>  		return nfserr_nametoolong;
> -	if (isdotent(str, len))
> +	if (name_is_dot_dotdot(str, len))
>  		return nfserr_badname;
>  	for (i = 0; i < len; i++)
>  		if (str[i] == '/')
> @@ -4241,7 +4241,7 @@ nfsd4_encode_entry4(void *ccdv, const char *name, int namlen,
>  	__be32 nfserr = nfserr_toosmall;
>  
>  	/* In nfsv4, "." and ".." never make it onto the wire.. */
> -	if (name && isdotent(name, namlen)) {
> +	if (name && name_is_dot_dotdot(name, namlen)) {
>  		cd->common.err = nfs_ok;
>  		return 0;
>  	}
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 7c009f07c90b..faf5c1dafa42 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -372,9 +372,6 @@ enum {
>  #define	nfserr_symlink_not_dir	cpu_to_be32(NFSERR_SYMLINK_NOT_DIR)
>  };
>  
> -/* Check for dir entries '.' and '..' */
> -#define isdotent(n, l)	(l < 3 && n[0] == '.' && (l == 1 || n[1] == '.'))
> -
>  #ifdef CONFIG_NFSD_V4
>  
>  /* before processing a COMPOUND operation, we have to check that there
> diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
> index 8873033d1e82..846506445ff9 100644
> --- a/fs/nfsd/nfsproc.c
> +++ b/fs/nfsd/nfsproc.c
> @@ -298,7 +298,7 @@ nfsd_proc_create(struct svc_rqst *rqstp)
>  	/* Check for NFSD_MAY_WRITE in nfsd_create if necessary */
>  
>  	resp->status = nfserr_exist;
> -	if (isdotent(argp->name, argp->len))
> +	if (name_is_dot_dotdot(argp->name, argp->len))
>  		goto done;
>  	hosterr = fh_want_write(dirfhp);
>  	if (hosterr) {
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index eafdf7b7890f..73506e924dc3 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -255,7 +255,7 @@ nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  	exp = exp_get(fhp->fh_export);
>  
>  	/* Lookup the name, but don't follow links */
> -	if (isdotent(name, len)) {
> +	if (name_is_dot_dotdot(name, len)) {
>  		if (len==1)
>  			dentry = dget(dparent);
>  		else if (dparent != exp->ex_path.dentry)
> @@ -1867,7 +1867,7 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  
>  	trace_nfsd_vfs_create(rqstp, fhp, type, fname, flen);
>  
> -	if (isdotent(fname, flen))
> +	if (name_is_dot_dotdot(fname, flen))
>  		return nfserr_exist;
>  
>  	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_NOP);
> @@ -1969,7 +1969,7 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  	if (!flen || path[0] == '\0')
>  		goto out;
>  	err = nfserr_exist;
> -	if (isdotent(fname, flen))
> +	if (name_is_dot_dotdot(fname, flen))
>  		goto out;
>  
>  	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
> @@ -2046,7 +2046,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
>  	if (!len)
>  		goto out;
>  	err = nfserr_exist;
> -	if (isdotent(name, len))
> +	if (name_is_dot_dotdot(name, len))
>  		goto out;
>  
>  	err = nfs_ok;
> @@ -2157,7 +2157,8 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
>  	tdentry = tfhp->fh_dentry;
>  
>  	err = nfserr_perm;
> -	if (!flen || isdotent(fname, flen) || !tlen || isdotent(tname, tlen))
> +	if (!flen || name_is_dot_dotdot(fname, flen) ||
> +	    !tlen || name_is_dot_dotdot(tname, tlen))
>  		goto out;
>  
>  	err = nfserr_xdev;
> @@ -2279,7 +2280,7 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
>  	trace_nfsd_vfs_unlink(rqstp, fhp, fname, flen);
>  
>  	err = nfserr_acces;
> -	if (!flen || isdotent(fname, flen))
> +	if (!flen || name_is_dot_dotdot(fname, flen))
>  		goto out;
>  	err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_REMOVE);
>  	if (err)

Reviewed-by: Jeff Layton <[email protected]>