linux-kernel - Re: [PATCH v3 06/38] vfs: break parent dir delegations in open(..., O

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Message-ID: <5cst6i2y5rjxsag3oihanh6nusjvaklw24t6ihdd6kyqsdxy7f@ld2vqj5yoexf>
Date: Fri, 26 Sep 2025 17:32:27 +0200
From: Jan Kara <jack@...e.cz>
To: Jeff Layton <jlayton@...nel.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, Chuck Lever <chuck.lever@...cle.com>, 
	Alexander Aring <alex.aring@...il.com>, Trond Myklebust <trondmy@...nel.org>, 
	Anna Schumaker <anna@...nel.org>, Steve French <sfrench@...ba.org>, 
	Ronnie Sahlberg <ronniesahlberg@...il.com>, Shyam Prasad N <sprasad@...rosoft.com>, 
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Subject: Re: [PATCH v3 06/38] vfs: break parent dir delegations in open(...,
 O_CREAT) codepath

On Wed 24-09-25 14:05:52, 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 lookup_open and have it break the
> delegation. Then, open_last_lookups can wait for the delegation break
> and retry the call to lookup_open once it's done.
> 
> Signed-off-by: Jeff Layton <jlayton@...nel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/namei.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 4e058b00208c1663ba828c6f8ed1f82c26a4f136..903b70a82530938a0fdf10508529a1b7cc38136d 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3609,7 +3609,7 @@ static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
>   */
>  static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
>  				  const struct open_flags *op,
> -				  bool got_write)
> +				  bool got_write, struct inode **delegated_inode)
>  {
>  	struct mnt_idmap *idmap;
>  	struct dentry *dir = nd->path.dentry;
> @@ -3698,6 +3698,11 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
>  
>  	/* Negative dentry, just create the file */
>  	if (!dentry->d_inode && (open_flag & O_CREAT)) {
> +		/* but break the directory lease first! */
> +		error = try_break_deleg(dir_inode, delegated_inode);
> +		if (error)
> +			goto out_dput;
> +
>  		file->f_mode |= FMODE_CREATED;
>  		audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
>  		if (!dir_inode->i_op->create) {
> @@ -3761,6 +3766,7 @@ static const char *open_last_lookups(struct nameidata *nd,
>  		   struct file *file, const struct open_flags *op)
>  {
>  	struct dentry *dir = nd->path.dentry;
> +	struct inode *delegated_inode = NULL;
>  	int open_flag = op->open_flag;
>  	bool got_write = false;
>  	struct dentry *dentry;
> @@ -3791,7 +3797,7 @@ static const char *open_last_lookups(struct nameidata *nd,
>  				return ERR_PTR(-ECHILD);
>  		}
>  	}
> -
> +retry:
>  	if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
>  		got_write = !mnt_want_write(nd->path.mnt);
>  		/*
> @@ -3804,7 +3810,7 @@ static const char *open_last_lookups(struct nameidata *nd,
>  		inode_lock(dir->d_inode);
>  	else
>  		inode_lock_shared(dir->d_inode);
> -	dentry = lookup_open(nd, file, op, got_write);
> +	dentry = lookup_open(nd, file, op, got_write, &delegated_inode);
>  	if (!IS_ERR(dentry)) {
>  		if (file->f_mode & FMODE_CREATED)
>  			fsnotify_create(dir->d_inode, dentry);
> @@ -3819,8 +3825,16 @@ static const char *open_last_lookups(struct nameidata *nd,
>  	if (got_write)
>  		mnt_drop_write(nd->path.mnt);
>  
> -	if (IS_ERR(dentry))
> +	if (IS_ERR(dentry)) {
> +		if (delegated_inode) {
> +			int error = break_deleg_wait(&delegated_inode);
> +
> +			if (!error)
> +				goto retry;
> +			return ERR_PTR(error);
> +		}
>  		return ERR_CAST(dentry);
> +	}
>  
>  	if (file->f_mode & (FMODE_OPENED | FMODE_CREATED)) {
>  		dput(nd->path.dentry);
> 
> -- 
> 2.51.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR