Re: [PATCH v2 09/14] nfsd: reduce range of directory lock in nfsd4_create_file()

On Mon, 2026-07-06 at 08:19 +1000, NeilBrown wrote:
> From: NeilBrown <neil-+NVA1uvv1dVBDLzU/[email protected]>
> 
> We only need to hold the lock taken by start_creating() until the create
> has been attempted.  Holding for longer can serve no purpose.
> 
> The lock is currently held across the setattr call.  This might be the
> intent but it serves no purpose.  Holding the lock prevents the name
> from being removed or renamed, but it doesn't prevent a GETATTR or a
> racing SETATTR or an OPEN.
> 
> Calling end_creating() puts the reference to 'child', but we can still
> use the reference that was stored in open->op_filp.
> 
> Signed-off-by: NeilBrown <neil-+NVA1uvv1dVBDLzU/[email protected]>
> ---
>  fs/nfsd/nfs4proc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 244d5f3975b7..973beda7f161 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -367,9 +367,12 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  		if (status == nfs_ok)
>  			open->op_created = open->op_filp->f_mode & FMODE_CREATED;
>  	}
> +	end_creating(child);
>  	if (status != nfs_ok)
>  		goto out;
>  
> +	child = open->op_filp->f_path.dentry;
> +
>  	status = fh_compose(resfhp, fhp->fh_export, child, fhp);
>  	if (status != nfs_ok)
>  		goto out;
> @@ -419,7 +422,6 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
>  	if (attrs.na_paclerr)
>  		open->op_bmval[2] &= ~FATTR4_WORD2_POSIX_ACCESS_ACL;
>  out:
> -	end_creating(child);
>  	fh_drop_write(fhp);
>  out_free:
>  	nfsd_attrs_free(&attrs);

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