Re: [PATCH 07/13] vfs: make vfs_create break delegations on parent directory

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2025-10-13 at 10:48 -0400, 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.
> 
> Rename vfs_create as __vfs_create, make it static, and add a new
> delegated_inode parameter. Fix do_mknodat to call __vfs_create and wait
> for a delegation break if there is one. Add a new exported vfs_create
> wrapper that passes in NULL for delegated_inode.
> 

My apologies. I meant to change this to just add the extra parameter to
vfs_create() without all of the wrapper nonsense. I'll plan to re-post
at least once more, but I'll wait a bit in case there are other changes
needed.

> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/namei.c | 55 ++++++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 36 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 786f42bd184b5dbf6d754fa1fb6c94c0f75429f2..1427c53e13978e70adefdc572b71247536985430 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3458,6 +3458,32 @@ static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap,
>  	return mode;
>  }
>  
> +static int __vfs_create(struct mnt_idmap *idmap, struct inode *dir,
> +			struct dentry *dentry, umode_t mode, bool want_excl,
> +			struct inode **delegated_inode)
> +{
> +	int error;
> +
> +	error = may_create(idmap, dir, dentry);
> +	if (error)
> +		return error;
> +
> +	if (!dir->i_op->create)
> +		return -EACCES;	/* shouldn't it be ENOSYS? */
> +
> +	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, delegated_inode);
> +	if (error)
> +		return error;
> +	error = dir->i_op->create(idmap, dir, dentry, mode, want_excl);
> +	if (!error)
> +		fsnotify_create(dir, dentry);
> +	return error;
> +}
> +
>  /**
>   * vfs_create - create new file
>   * @idmap:	idmap of the mount the inode was found from
> @@ -3477,23 +3503,7 @@ static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap,
>  int vfs_create(struct mnt_idmap *idmap, struct inode *dir,
>  	       struct dentry *dentry, umode_t mode, bool want_excl)
>  {
> -	int error;
> -
> -	error = may_create(idmap, dir, dentry);
> -	if (error)
> -		return error;
> -
> -	if (!dir->i_op->create)
> -		return -EACCES;	/* shouldn't it be ENOSYS? */
> -
> -	mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
> -	error = security_inode_create(dir, dentry, mode);
> -	if (error)
> -		return error;
> -	error = dir->i_op->create(idmap, dir, dentry, mode, want_excl);
> -	if (!error)
> -		fsnotify_create(dir, dentry);
> -	return error;
> +	return __vfs_create(idmap, dir, dentry, mode, want_excl, NULL);
>  }
>  EXPORT_SYMBOL(vfs_create);
>  
> @@ -4365,6 +4375,7 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
>  	struct path path;
>  	int error;
>  	unsigned int lookup_flags = 0;
> +	struct inode *delegated_inode = NULL;
>  
>  	error = may_mknod(mode);
>  	if (error)
> @@ -4383,8 +4394,9 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
>  	idmap = mnt_idmap(path.mnt);
>  	switch (mode & S_IFMT) {
>  		case 0: case S_IFREG:
> -			error = vfs_create(idmap, path.dentry->d_inode,
> -					   dentry, mode, true);
> +			error = __vfs_create(idmap, path.dentry->d_inode,
> +					     dentry, mode, true,
> +					     &delegated_inode);
>  			if (!error)
>  				security_path_post_mknod(idmap, dentry);
>  			break;
> @@ -4399,6 +4411,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
>  	}
>  out2:
>  	end_creating_path(&path, dentry);
> +	if (delegated_inode) {
> +		error = break_deleg_wait(&delegated_inode);
> +		if (!error)
> +			goto retry;
> +	}
>  	if (retry_estale(error, lookup_flags)) {
>  		lookup_flags |= LOOKUP_REVAL;
>  		goto retry;

-- 
Jeff Layton <jlayton@kernel.org>