In order to add directory delegation support, we need to break
delegations on the parent whenever there is going to be a change in the
directory.

Add a delegated_inode parameter to struct createdata. Most callers just
leave that as a NULL pointer, but do_mknodat() is changed to wait for a
delegation break if there is one.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/namei.c         | 26 +++++++++++++++++---------
 include/linux/fs.h |  2 +-
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index fdf4e78cd041de8c564b7d1d89a46ba2aaf79d53..e8973000a312fb05ebb63a0d9bd83b9a5f8f805d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3487,6 +3487,9 @@ int vfs_create(struct createdata *args)
 
 	mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
 	error = security_inode_create(dir, dentry, mode);
+	if (error)
+		return error;
+	error = try_break_deleg(dir, args->delegated_inode);
 	if (error)
 		return error;
 	error = dir->i_op->create(idmap, dir, dentry, mode, args->excl);
@@ -4359,6 +4362,8 @@ static int may_mknod(umode_t mode)
 static int do_mknodat(int dfd, struct filename *name, umode_t mode,
 		unsigned int dev)
 {
+	struct delegated_inode delegated_inode = { };
+	struct createdata cargs = { };
 	struct mnt_idmap *idmap;
 	struct dentry *dentry;
 	struct path path;
@@ -4383,18 +4388,16 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
 	switch (mode & S_IFMT) {
 		case 0:
 		case S_IFREG:
-		{
-			struct createdata args = { .idmap = idmap,
-						   .dir = path.dentry->d_inode,
-						   .dentry = dentry,
-						   .mode = mode,
-						   .excl = true };
-
-			error = vfs_create(&args);
+			cargs.idmap = idmap,
+			cargs.dir = path.dentry->d_inode,
+			cargs.dentry = dentry,
+			cargs.delegated_inode = &delegated_inode;
+			cargs.mode = mode,
+			cargs.excl = true,
+			error = vfs_create(&cargs);
 			if (!error)
 				security_path_post_mknod(idmap, dentry);
 			break;
-		}
 		case S_IFCHR: case S_IFBLK:
 			error = vfs_mknod(idmap, path.dentry->d_inode,
 					  dentry, mode, new_decode_dev(dev));
@@ -4406,6 +4409,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
 	}
 out2:
 	end_creating_path(&path, dentry);
+	if (is_delegated(&delegated_inode)) {
+		error = break_deleg_wait(&delegated_inode);
+		if (!error)
+			goto retry;
+	}
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b61873767b37591aecadd147623d7dfc866bef82..cfcb20a7c4ce4b6dcec98b3eccbdb5ec8bab6fa9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2116,12 +2116,12 @@ struct createdata {
 	struct mnt_idmap *idmap;	// idmap of the mount the inode was found from
 	struct inode *dir;		// inode of parent directory
 	struct dentry *dentry;		// dentry of the child file
+	struct delegated_inode *delegated_inode; // returns parent inode, if delegated
 	umode_t mode;			// mode of the child file
 	bool excl;			// whether the file must not yet exist
 };
 
 int vfs_create(struct createdata *);
-
 struct dentry *vfs_mkdir(struct mnt_idmap *, struct inode *,
 			 struct dentry *, umode_t, struct delegated_inode *);
 int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,

-- 
2.51.1

On Mon, Nov 03, 2025 at 07:52:38AM -0500, Jeff Layton wrote:
> In order to add directory delegation support, we need to break
> delegations on the parent whenever there is going to be a change in the
> directory.
> 
> Add a delegated_inode parameter to struct createdata. Most callers just
> leave that as a NULL pointer, but do_mknodat() is changed to wait for a
> delegation break if there is one.
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/namei.c         | 26 +++++++++++++++++---------
>  include/linux/fs.h |  2 +-
>  2 files changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c

...

> @@ -4359,6 +4362,8 @@ static int may_mknod(umode_t mode)
>  static int do_mknodat(int dfd, struct filename *name, umode_t mode,
>  		unsigned int dev)
>  {
> +	struct delegated_inode delegated_inode = { };
> +	struct createdata cargs = { };
>  	struct mnt_idmap *idmap;
>  	struct dentry *dentry;
>  	struct path path;
> @@ -4383,18 +4388,16 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
>  	switch (mode & S_IFMT) {
>  		case 0:
>  		case S_IFREG:
> -		{
> -			struct createdata args = { .idmap = idmap,
> -						   .dir = path.dentry->d_inode,
> -						   .dentry = dentry,
> -						   .mode = mode,
> -						   .excl = true };
> -
> -			error = vfs_create(&args);
> +			cargs.idmap = idmap,
> +			cargs.dir = path.dentry->d_inode,
> +			cargs.dentry = dentry,
> +			cargs.delegated_inode = &delegated_inode;
> +			cargs.mode = mode,
> +			cargs.excl = true,

Hi Jeff,

I don't think it makes any difference to the generated code.
But I think it would be more intuitive to use ';' rather than ','
at the end of the lines immediately above.

> +			error = vfs_create(&cargs);
>  			if (!error)
>  				security_path_post_mknod(idmap, dentry);
>  			break;
> -		}
>  		case S_IFCHR: case S_IFBLK:
>  			error = vfs_mknod(idmap, path.dentry->d_inode,
>  					  dentry, mode, new_decode_dev(dev));

...

On Tue, 2025-11-04 at 17:38 +0000, Simon Horman wrote:
> On Mon, Nov 03, 2025 at 07:52:38AM -0500, Jeff Layton wrote:
> > In order to add directory delegation support, we need to break
> > delegations on the parent whenever there is going to be a change in the
> > directory.
> > 
> > Add a delegated_inode parameter to struct createdata. Most callers just
> > leave that as a NULL pointer, but do_mknodat() is changed to wait for a
> > delegation break if there is one.
> > 
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> >  fs/namei.c         | 26 +++++++++++++++++---------
> >  include/linux/fs.h |  2 +-
> >  2 files changed, 18 insertions(+), 10 deletions(-)
> > 
> > diff --git a/fs/namei.c b/fs/namei.c
> 
> ...
> 
> > @@ -4359,6 +4362,8 @@ static int may_mknod(umode_t mode)
> >  static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> >  		unsigned int dev)
> >  {
> > +	struct delegated_inode delegated_inode = { };
> > +	struct createdata cargs = { };
> >  	struct mnt_idmap *idmap;
> >  	struct dentry *dentry;
> >  	struct path path;
> > @@ -4383,18 +4388,16 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> >  	switch (mode & S_IFMT) {
> >  		case 0:
> >  		case S_IFREG:
> > -		{
> > -			struct createdata args = { .idmap = idmap,
> > -						   .dir = path.dentry->d_inode,
> > -						   .dentry = dentry,
> > -						   .mode = mode,
> > -						   .excl = true };
> > -
> > -			error = vfs_create(&args);
> > +			cargs.idmap = idmap,
> > +			cargs.dir = path.dentry->d_inode,
> > +			cargs.dentry = dentry,
> > +			cargs.delegated_inode = &delegated_inode;
> > +			cargs.mode = mode,
> > +			cargs.excl = true,
> 
> Hi Jeff,
> 
> I don't think it makes any difference to the generated code.
> But I think it would be more intuitive to use ';' rather than ','
> at the end of the lines immediately above.
> 

Definitely. Will fix.

> > +			error = vfs_create(&cargs);
> >  			if (!error)
> >  				security_path_post_mknod(idmap, dentry);
> >  			break;
> > -		}
> >  		case S_IFCHR: case S_IFBLK:
> >  			error = vfs_mknod(idmap, path.dentry->d_inode,
> >  					  dentry, mode, new_decode_dev(dev));
> 
> ...

Thanks!
-- 
Jeff Layton <jlayton@kernel.org>

On Mon, 03 Nov 2025, Jeff Layton wrote:
> In order to add directory delegation support, we need to break
> delegations on the parent whenever there is going to be a change in the
> directory.
> 
> Add a delegated_inode parameter to struct createdata. Most callers just
> leave that as a NULL pointer, but do_mknodat() is changed to wait for a
> delegation break if there is one.
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/namei.c         | 26 +++++++++++++++++---------
>  include/linux/fs.h |  2 +-
>  2 files changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index fdf4e78cd041de8c564b7d1d89a46ba2aaf79d53..e8973000a312fb05ebb63a0d9bd83b9a5f8f805d 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3487,6 +3487,9 @@ int vfs_create(struct createdata *args)
>  
>  	mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
>  	error = security_inode_create(dir, dentry, mode);
> +	if (error)
> +		return error;
> +	error = try_break_deleg(dir, args->delegated_inode);
>  	if (error)
>  		return error;
>  	error = dir->i_op->create(idmap, dir, dentry, mode, args->excl);
> @@ -4359,6 +4362,8 @@ static int may_mknod(umode_t mode)
>  static int do_mknodat(int dfd, struct filename *name, umode_t mode,
>  		unsigned int dev)
>  {
> +	struct delegated_inode delegated_inode = { };
> +	struct createdata cargs = { };

If we must have 'createdata', can it have a 'struct delegated_inode'
rather than a pointer to it?

NeilBrown


>  	struct mnt_idmap *idmap;
>  	struct dentry *dentry;
>  	struct path path;
> @@ -4383,18 +4388,16 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
>  	switch (mode & S_IFMT) {
>  		case 0:
>  		case S_IFREG:
> -		{
> -			struct createdata args = { .idmap = idmap,
> -						   .dir = path.dentry->d_inode,
> -						   .dentry = dentry,
> -						   .mode = mode,
> -						   .excl = true };
> -
> -			error = vfs_create(&args);
> +			cargs.idmap = idmap,
> +			cargs.dir = path.dentry->d_inode,
> +			cargs.dentry = dentry,
> +			cargs.delegated_inode = &delegated_inode;
> +			cargs.mode = mode,
> +			cargs.excl = true,
> +			error = vfs_create(&cargs);
>  			if (!error)
>  				security_path_post_mknod(idmap, dentry);
>  			break;
> -		}
>  		case S_IFCHR: case S_IFBLK:
>  			error = vfs_mknod(idmap, path.dentry->d_inode,
>  					  dentry, mode, new_decode_dev(dev));
> @@ -4406,6 +4409,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
>  	}
>  out2:
>  	end_creating_path(&path, dentry);
> +	if (is_delegated(&delegated_inode)) {
> +		error = break_deleg_wait(&delegated_inode);
> +		if (!error)
> +			goto retry;
> +	}
>  	if (retry_estale(error, lookup_flags)) {
>  		lookup_flags |= LOOKUP_REVAL;
>  		goto retry;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index b61873767b37591aecadd147623d7dfc866bef82..cfcb20a7c4ce4b6dcec98b3eccbdb5ec8bab6fa9 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2116,12 +2116,12 @@ struct createdata {
>  	struct mnt_idmap *idmap;	// idmap of the mount the inode was found from
>  	struct inode *dir;		// inode of parent directory
>  	struct dentry *dentry;		// dentry of the child file
> +	struct delegated_inode *delegated_inode; // returns parent inode, if delegated
>  	umode_t mode;			// mode of the child file
>  	bool excl;			// whether the file must not yet exist
>  };
>  
>  int vfs_create(struct createdata *);
> -
>  struct dentry *vfs_mkdir(struct mnt_idmap *, struct inode *,
>  			 struct dentry *, umode_t, struct delegated_inode *);
>  int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
> 
> -- 
> 2.51.1
> 
> 

On Tue, 2025-11-04 at 11:14 +1100, NeilBrown wrote:
> On Mon, 03 Nov 2025, Jeff Layton wrote:
> > In order to add directory delegation support, we need to break
> > delegations on the parent whenever there is going to be a change in the
> > directory.
> > 
> > Add a delegated_inode parameter to struct createdata. Most callers just
> > leave that as a NULL pointer, but do_mknodat() is changed to wait for a
> > delegation break if there is one.
> > 
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> >  fs/namei.c         | 26 +++++++++++++++++---------
> >  include/linux/fs.h |  2 +-
> >  2 files changed, 18 insertions(+), 10 deletions(-)
> > 
> > diff --git a/fs/namei.c b/fs/namei.c
> > index fdf4e78cd041de8c564b7d1d89a46ba2aaf79d53..e8973000a312fb05ebb63a0d9bd83b9a5f8f805d 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -3487,6 +3487,9 @@ int vfs_create(struct createdata *args)
> >  
> >  	mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
> >  	error = security_inode_create(dir, dentry, mode);
> > +	if (error)
> > +		return error;
> > +	error = try_break_deleg(dir, args->delegated_inode);
> >  	if (error)
> >  		return error;
> >  	error = dir->i_op->create(idmap, dir, dentry, mode, args->excl);
> > @@ -4359,6 +4362,8 @@ static int may_mknod(umode_t mode)
> >  static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> >  		unsigned int dev)
> >  {
> > +	struct delegated_inode delegated_inode = { };
> > +	struct createdata cargs = { };
> 
> If we must have 'createdata', can it have a 'struct delegated_inode'
> rather than a pointer to it?
> 

If we do that, then we'd need some way to signal that the caller
doesn't want to wait on the delegation break. Currently that's
indicated by setting cargs.delegated_inode to NULL. I suppose we could
add a bool for this or something.

I confess that I too am lukewarm on struct createdata. I can live with
it, but it's not clearly a win to me either.

Christian, thoughts?

> 
> >  	struct mnt_idmap *idmap;
> >  	struct dentry *dentry;
> >  	struct path path;
> > @@ -4383,18 +4388,16 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> >  	switch (mode & S_IFMT) {
> >  		case 0:
> >  		case S_IFREG:
> > -		{
> > -			struct createdata args = { .idmap = idmap,
> > -						   .dir = path.dentry->d_inode,
> > -						   .dentry = dentry,
> > -						   .mode = mode,
> > -						   .excl = true };
> > -
> > -			error = vfs_create(&args);
> > +			cargs.idmap = idmap,
> > +			cargs.dir = path.dentry->d_inode,
> > +			cargs.dentry = dentry,
> > +			cargs.delegated_inode = &delegated_inode;
> > +			cargs.mode = mode,
> > +			cargs.excl = true,
> > +			error = vfs_create(&cargs);
> >  			if (!error)
> >  				security_path_post_mknod(idmap, dentry);
> >  			break;
> > -		}
> >  		case S_IFCHR: case S_IFBLK:
> >  			error = vfs_mknod(idmap, path.dentry->d_inode,
> >  					  dentry, mode, new_decode_dev(dev));
> > @@ -4406,6 +4409,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> >  	}
> >  out2:
> >  	end_creating_path(&path, dentry);
> > +	if (is_delegated(&delegated_inode)) {
> > +		error = break_deleg_wait(&delegated_inode);
> > +		if (!error)
> > +			goto retry;
> > +	}
> >  	if (retry_estale(error, lookup_flags)) {
> >  		lookup_flags |= LOOKUP_REVAL;
> >  		goto retry;
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index b61873767b37591aecadd147623d7dfc866bef82..cfcb20a7c4ce4b6dcec98b3eccbdb5ec8bab6fa9 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -2116,12 +2116,12 @@ struct createdata {
> >  	struct mnt_idmap *idmap;	// idmap of the mount the inode was found from
> >  	struct inode *dir;		// inode of parent directory
> >  	struct dentry *dentry;		// dentry of the child file
> > +	struct delegated_inode *delegated_inode; // returns parent inode, if delegated
> >  	umode_t mode;			// mode of the child file
> >  	bool excl;			// whether the file must not yet exist
> >  };
> >  
> >  int vfs_create(struct createdata *);
> > -
> >  struct dentry *vfs_mkdir(struct mnt_idmap *, struct inode *,
> >  			 struct dentry *, umode_t, struct delegated_inode *);
> >  int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
> > 
> > -- 
> > 2.51.1
> > 
> > 

-- 
Jeff Layton <jlayton@kernel.org>

On Mon, Nov 03, 2025 at 07:30:57PM -0500, Jeff Layton wrote:
> On Tue, 2025-11-04 at 11:14 +1100, NeilBrown wrote:
> > On Mon, 03 Nov 2025, Jeff Layton wrote:
> > > In order to add directory delegation support, we need to break
> > > delegations on the parent whenever there is going to be a change in the
> > > directory.
> > > 
> > > Add a delegated_inode parameter to struct createdata. Most callers just
> > > leave that as a NULL pointer, but do_mknodat() is changed to wait for a
> > > delegation break if there is one.
> > > 
> > > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > > ---
> > >  fs/namei.c         | 26 +++++++++++++++++---------
> > >  include/linux/fs.h |  2 +-
> > >  2 files changed, 18 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/fs/namei.c b/fs/namei.c
> > > index fdf4e78cd041de8c564b7d1d89a46ba2aaf79d53..e8973000a312fb05ebb63a0d9bd83b9a5f8f805d 100644
> > > --- a/fs/namei.c
> > > +++ b/fs/namei.c
> > > @@ -3487,6 +3487,9 @@ int vfs_create(struct createdata *args)
> > >  
> > >  	mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
> > >  	error = security_inode_create(dir, dentry, mode);
> > > +	if (error)
> > > +		return error;
> > > +	error = try_break_deleg(dir, args->delegated_inode);
> > >  	if (error)
> > >  		return error;
> > >  	error = dir->i_op->create(idmap, dir, dentry, mode, args->excl);
> > > @@ -4359,6 +4362,8 @@ static int may_mknod(umode_t mode)
> > >  static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> > >  		unsigned int dev)
> > >  {
> > > +	struct delegated_inode delegated_inode = { };
> > > +	struct createdata cargs = { };
> > 
> > If we must have 'createdata', can it have a 'struct delegated_inode'
> > rather than a pointer to it?
> > 
> 
> If we do that, then we'd need some way to signal that the caller
> doesn't want to wait on the delegation break. Currently that's
> indicated by setting cargs.delegated_inode to NULL. I suppose we could
> add a bool for this or something.
> 
> I confess that I too am lukewarm on struct createdata. I can live with
> it, but it's not clearly a win to me either.
> 
> Christian, thoughts?

If two stable voices of the community seem to have consensus that this
isn't worth it then it's obviously fine to not do it.

> 
> > 
> > >  	struct mnt_idmap *idmap;
> > >  	struct dentry *dentry;
> > >  	struct path path;
> > > @@ -4383,18 +4388,16 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> > >  	switch (mode & S_IFMT) {
> > >  		case 0:
> > >  		case S_IFREG:
> > > -		{
> > > -			struct createdata args = { .idmap = idmap,
> > > -						   .dir = path.dentry->d_inode,
> > > -						   .dentry = dentry,
> > > -						   .mode = mode,
> > > -						   .excl = true };
> > > -
> > > -			error = vfs_create(&args);
> > > +			cargs.idmap = idmap,
> > > +			cargs.dir = path.dentry->d_inode,
> > > +			cargs.dentry = dentry,
> > > +			cargs.delegated_inode = &delegated_inode;
> > > +			cargs.mode = mode,
> > > +			cargs.excl = true,
> > > +			error = vfs_create(&cargs);
> > >  			if (!error)
> > >  				security_path_post_mknod(idmap, dentry);
> > >  			break;
> > > -		}
> > >  		case S_IFCHR: case S_IFBLK:
> > >  			error = vfs_mknod(idmap, path.dentry->d_inode,
> > >  					  dentry, mode, new_decode_dev(dev));
> > > @@ -4406,6 +4409,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> > >  	}
> > >  out2:
> > >  	end_creating_path(&path, dentry);
> > > +	if (is_delegated(&delegated_inode)) {
> > > +		error = break_deleg_wait(&delegated_inode);
> > > +		if (!error)
> > > +			goto retry;
> > > +	}
> > >  	if (retry_estale(error, lookup_flags)) {
> > >  		lookup_flags |= LOOKUP_REVAL;
> > >  		goto retry;
> > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > index b61873767b37591aecadd147623d7dfc866bef82..cfcb20a7c4ce4b6dcec98b3eccbdb5ec8bab6fa9 100644
> > > --- a/include/linux/fs.h
> > > +++ b/include/linux/fs.h
> > > @@ -2116,12 +2116,12 @@ struct createdata {
> > >  	struct mnt_idmap *idmap;	// idmap of the mount the inode was found from
> > >  	struct inode *dir;		// inode of parent directory
> > >  	struct dentry *dentry;		// dentry of the child file
> > > +	struct delegated_inode *delegated_inode; // returns parent inode, if delegated
> > >  	umode_t mode;			// mode of the child file
> > >  	bool excl;			// whether the file must not yet exist
> > >  };
> > >  
> > >  int vfs_create(struct createdata *);
> > > -
> > >  struct dentry *vfs_mkdir(struct mnt_idmap *, struct inode *,
> > >  			 struct dentry *, umode_t, struct delegated_inode *);
> > >  int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
> > > 
> > > -- 
> > > 2.51.1
> > > 
> > > 
> 
> -- 
> Jeff Layton <jlayton@kernel.org>