diff mbox series

[5/6] nfs: change mkdir inode_operation to return alternate dentry if needed.

Message ID 20250220234630.983190-6-neilb@suse.de (mailing list archive)
State Handled Elsewhere
Headers show
Series Change ->mkdir() and vfs_mkdir() to return a dentry. | expand

Commit Message

NeilBrown Feb. 20, 2025, 11:36 p.m. UTC 
mkdir now allows a different dentry to be returned which is sometimes
relevant for nfs.

This patch changes the nfs_rpc_ops mkdir op to return a dentry, and
passes that back to the caller.

The mkdir nfs_rpc_op will return NULL if the original dentry should be
used.  This matches the mkdir inode_operation.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/nfs/dir.c            | 13 ++++---------
 fs/nfs/nfs3proc.c       |  9 ++++++---
 fs/nfs/nfs4proc.c       | 43 +++++++++++++++++++++++++++++------------
 fs/nfs/proc.c           | 12 ++++++++----
 include/linux/nfs_xdr.h |  2 +-
 5 files changed, 50 insertions(+), 29 deletions(-)

Comments

Al Viro Feb. 22, 2025, 4:41 a.m. UTC | #1 
On Fri, Feb 21, 2025 at 10:36:34AM +1100, NeilBrown wrote:

>  nfs3_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
>  {
>  	struct posix_acl *default_acl, *acl;
> @@ -612,15 +612,18 @@ nfs3_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
>  		dentry = d_alias;
>  
>  	status = nfs3_proc_setacls(d_inode(dentry), acl, default_acl);
> +	if (status && d_alias)
> +		dput(d_alias);
>  
> -	dput(d_alias);
>  out_release_acls:
>  	posix_acl_release(acl);
>  	posix_acl_release(default_acl);
>  out:
>  	nfs3_free_createdata(data);
>  	dprintk("NFS reply mkdir: %d\n", status);
> -	return status;
> +	if (status)
> +		return ERR_PTR(status);
> +	return d_alias;

Ugh...  That's really hard to follow - you are leaving a dangling
reference in d_alias textually upstream of using that variable.
The only reason it's not a bug is that dput() is reachable only
with status && d_alias and that guarantees that we'll
actually go away on if (status) return ERR_PTR(status).

Worse, you can reach 'out:' with d_alias uninitialized.  Yes,
all such branches happen with status either still unmodified
since it's initialization (which is non-zero) or under
if (status), so again, that return d_alias; is unreachable.

So the code is correct, but it's really asking for trouble down
the road.

BTW, dput(NULL) is guaranteed to be a no-op...
diff mbox series

Patch

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 101b1098e87b..bc957487f6ec 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2426,7 +2426,7 @@  struct dentry *nfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 			 struct dentry *dentry, umode_t mode)
 {
 	struct iattr attr;
-	int error;
+	struct dentry *ret;
 
 	dfprintk(VFS, "NFS: mkdir(%s/%lu), %pd\n",
 			dir->i_sb->s_id, dir->i_ino, dentry);
@@ -2435,14 +2435,9 @@  struct dentry *nfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	attr.ia_mode = mode | S_IFDIR;
 
 	trace_nfs_mkdir_enter(dir, dentry);
-	error = NFS_PROTO(dir)->mkdir(dir, dentry, &attr);
-	trace_nfs_mkdir_exit(dir, dentry, error);
-	if (error != 0)
-		goto out_err;
-	return NULL;
-out_err:
-	d_drop(dentry);
-	return ERR_PTR(error);
+	ret = NFS_PROTO(dir)->mkdir(dir, dentry, &attr);
+	trace_nfs_mkdir_exit(dir, dentry, PTR_ERR_OR_ZERO(ret));
+	return ret;
 }
 EXPORT_SYMBOL_GPL(nfs_mkdir);
 
diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c
index 0c3bc98cd999..dfb3fafc9d4f 100644
--- a/fs/nfs/nfs3proc.c
+++ b/fs/nfs/nfs3proc.c
@@ -578,7 +578,7 @@  nfs3_proc_symlink(struct inode *dir, struct dentry *dentry, struct folio *folio,
 	return status;
 }
 
-static int
+static struct dentry *
 nfs3_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 {
 	struct posix_acl *default_acl, *acl;
@@ -612,15 +612,18 @@  nfs3_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 		dentry = d_alias;
 
 	status = nfs3_proc_setacls(d_inode(dentry), acl, default_acl);
+	if (status && d_alias)
+		dput(d_alias);
 
-	dput(d_alias);
 out_release_acls:
 	posix_acl_release(acl);
 	posix_acl_release(default_acl);
 out:
 	nfs3_free_createdata(data);
 	dprintk("NFS reply mkdir: %d\n", status);
-	return status;
+	if (status)
+		return ERR_PTR(status);
+	return d_alias;
 }
 
 static int
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index df9669d4ded7..164c9f3f36c8 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5135,9 +5135,6 @@  static int nfs4_do_create(struct inode *dir, struct dentry *dentry, struct nfs4_
 				    &data->arg.seq_args, &data->res.seq_res, 1);
 	if (status == 0) {
 		spin_lock(&dir->i_lock);
-		/* Creating a directory bumps nlink in the parent */
-		if (data->arg.ftype == NF4DIR)
-			nfs4_inc_nlink_locked(dir);
 		nfs4_update_changeattr_locked(dir, &data->res.dir_cinfo,
 					      data->res.fattr->time_start,
 					      NFS_INO_INVALID_DATA);
@@ -5147,6 +5144,25 @@  static int nfs4_do_create(struct inode *dir, struct dentry *dentry, struct nfs4_
 	return status;
 }
 
+static struct dentry *nfs4_do_mkdir(struct inode *dir, struct dentry *dentry,
+				    struct nfs4_createdata *data)
+{
+	int status = nfs4_call_sync(NFS_SERVER(dir)->client, NFS_SERVER(dir), &data->msg,
+				    &data->arg.seq_args, &data->res.seq_res, 1);
+
+	if (status)
+		return ERR_PTR(status);
+
+	spin_lock(&dir->i_lock);
+	/* Creating a directory bumps nlink in the parent */
+	nfs4_inc_nlink_locked(dir);
+	nfs4_update_changeattr_locked(dir, &data->res.dir_cinfo,
+				      data->res.fattr->time_start,
+				      NFS_INO_INVALID_DATA);
+	spin_unlock(&dir->i_lock);
+	return nfs_add_or_obtain(dentry, data->res.fh, data->res.fattr);
+}
+
 static void nfs4_free_createdata(struct nfs4_createdata *data)
 {
 	nfs4_label_free(data->fattr.label);
@@ -5203,32 +5219,34 @@  static int nfs4_proc_symlink(struct inode *dir, struct dentry *dentry,
 	return err;
 }
 
-static int _nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
-		struct iattr *sattr, struct nfs4_label *label)
+static struct dentry *_nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
+				       struct iattr *sattr,
+				       struct nfs4_label *label)
 {
 	struct nfs4_createdata *data;
-	int status = -ENOMEM;
+	struct dentry *ret = ERR_PTR(-ENOMEM);
 
 	data = nfs4_alloc_createdata(dir, &dentry->d_name, sattr, NF4DIR);
 	if (data == NULL)
 		goto out;
 
 	data->arg.label = label;
-	status = nfs4_do_create(dir, dentry, data);
+	ret = nfs4_do_mkdir(dir, dentry, data);
 
 	nfs4_free_createdata(data);
 out:
-	return status;
+	return ret;
 }
 
-static int nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
-		struct iattr *sattr)
+static struct dentry *nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
+				      struct iattr *sattr)
 {
 	struct nfs_server *server = NFS_SERVER(dir);
 	struct nfs4_exception exception = {
 		.interruptible = true,
 	};
 	struct nfs4_label l, *label;
+	struct dentry *alias;
 	int err;
 
 	label = nfs4_label_init_security(dir, dentry, sattr, &l);
@@ -5236,14 +5254,15 @@  static int nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
 	if (!(server->attr_bitmask[2] & FATTR4_WORD2_MODE_UMASK))
 		sattr->ia_mode &= ~current_umask();
 	do {
-		err = _nfs4_proc_mkdir(dir, dentry, sattr, label);
+		alias = _nfs4_proc_mkdir(dir, dentry, sattr, label);
+		err = PTR_ERR_OR_ZERO(alias);
 		trace_nfs4_mkdir(dir, &dentry->d_name, err);
 		err = nfs4_handle_exception(NFS_SERVER(dir), err,
 				&exception);
 	} while (exception.retry);
 	nfs4_label_release_security(label);
 
-	return err;
+	return alias;
 }
 
 static int _nfs4_proc_readdir(struct nfs_readdir_arg *nr_arg,
diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c
index 77920a2e3cef..63e71310b9f6 100644
--- a/fs/nfs/proc.c
+++ b/fs/nfs/proc.c
@@ -446,13 +446,14 @@  nfs_proc_symlink(struct inode *dir, struct dentry *dentry, struct folio *folio,
 	return status;
 }
 
-static int
+static struct dentry *
 nfs_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 {
 	struct nfs_createdata *data;
 	struct rpc_message msg = {
 		.rpc_proc	= &nfs_procedures[NFSPROC_MKDIR],
 	};
+	struct dentry *alias = NULL;
 	int status = -ENOMEM;
 
 	dprintk("NFS call  mkdir %pd\n", dentry);
@@ -464,12 +465,15 @@  nfs_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 
 	status = rpc_call_sync(NFS_CLIENT(dir), &msg, 0);
 	nfs_mark_for_revalidate(dir);
-	if (status == 0)
-		status = nfs_instantiate(dentry, data->res.fh, data->res.fattr);
+	if (status == 0) {
+		alias = nfs_add_or_obtain(dentry, data->res.fh, data->res.fattr);
+		status = PTR_ERR_OR_ZERO(alias);
+	} else
+		alias = ERR_PTR(status);
 	nfs_free_createdata(data);
 out:
 	dprintk("NFS reply mkdir: %d\n", status);
-	return status;
+	return alias;
 }
 
 static int
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 9155a6ffc370..d66c61cbbd1d 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -1802,7 +1802,7 @@  struct nfs_rpc_ops {
 	int	(*link)    (struct inode *, struct inode *, const struct qstr *);
 	int	(*symlink) (struct inode *, struct dentry *, struct folio *,
 			    unsigned int, struct iattr *);
-	int	(*mkdir)   (struct inode *, struct dentry *, struct iattr *);
+	struct dentry *(*mkdir)   (struct inode *, struct dentry *, struct iattr *);
 	int	(*rmdir)   (struct inode *, const struct qstr *);
 	int	(*readdir) (struct nfs_readdir_arg *, struct nfs_readdir_res *);
 	int	(*mknod)   (struct inode *, struct dentry *, struct iattr *,