linux-kernel - Re: [PATCH v3 27/38] nfsd: add notification handlers for dir events

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Message-ID: <8e5d91125e171f8ee3cd6a10dfb47a6d25fb83c9.camel@kernel.org>
Date: Thu, 25 Sep 2025 13:15:54 -0400
From: Jeff Layton <jlayton@...nel.org>
To: 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>, Tom Talpey <tom@...pey.com>, 
 Bharath SM <bharathsm@...rosoft.com>, NeilBrown <neil@...wn.name>, Olga
 Kornievskaia <okorniev@...hat.com>,  Dai Ngo <Dai.Ngo@...cle.com>, Jonathan
 Corbet <corbet@....net>, Amir Goldstein <amir73il@...il.com>,  Miklos
 Szeredi <miklos@...redi.hu>, Paulo Alcantara <pc@...guebit.org>, Greg
 Kroah-Hartman	 <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>,  Danilo Krummrich	 <dakr@...nel.org>, David Howells
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 <linkinjeon@...nel.org>, Steve French	 <smfrench@...il.com>, Sergey
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 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu	
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Rick Macklem <rick.macklem@...il.com>, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org, 
	linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org, 
	linux-doc@...r.kernel.org, netfs@...ts.linux.dev, ecryptfs@...r.kernel.org,
 	linux-unionfs@...r.kernel.org, linux-xfs@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v3 27/38] nfsd: add notification handlers for dir events

On Wed, 2025-09-24 at 14:06 -0400, Jeff Layton wrote:
> Add the necessary parts to accept a fsnotify callback for directory
> change event and create a CB_NOTIFY request for it. When a dir nfsd_file
> is created set a handle_event callback to handle the notification.
> 
> Use that to allocate a nfsd_notify_event object and then hand off a
> reference to each delegation's CB_NOTIFY. If anything fails along the
> way, recall any affected delegations.
> 
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
>  fs/nfsd/filecache.c    |  51 ++++++++++----
>  fs/nfsd/nfs4callback.c |  19 +++--
>  fs/nfsd/nfs4state.c    | 185 +++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/nfsd/nfs4xdr.c      |  95 +++++++++++++++++++++++++
>  fs/nfsd/state.h        |   2 +
>  fs/nfsd/xdr4.h         |   2 +
>  6 files changed, 337 insertions(+), 17 deletions(-)
> 

[...]

> +
> +int
> +nfsd_handle_dir_event(u32 mask, const struct inode *dir, const void *data,
> +		      int data_type, const struct qstr *name)
> +{
> +	struct dentry *dentry = fsnotify_data_dentry(data, data_type);
> +	struct file_lock_context *ctx;
> +	struct file_lock_core *flc;
> +	struct nfsd_notify_event *evt;
> +
> +	ctx = locks_inode_context(dir);
> +	if (!ctx || list_empty(&ctx->flc_lease))
> +		return 0;
> +
> +	evt = alloc_nfsd_notify_event(mask, name, dentry);
> +	if (!evt) {
> +		nfsd_recall_all_dir_delegs(dir);
> +		return 0;
> +	}
> +
> +	spin_lock(&ctx->flc_lock);
> +	list_for_each_entry(flc, &ctx->flc_lease, flc_list) {
> +		struct file_lease *fl = container_of(flc, struct file_lease, c);
> +		struct nfs4_delegation *dp = flc->flc_owner;
> +		struct nfsd4_cb_notify *ncn = &dp->dl_cb_notify;
> +
> +		if (!should_notify_deleg(mask, fl))
> +			continue;
> +
> +		spin_lock(&ncn->ncn_lock);
> +		if (ncn->ncn_evt_cnt >= NOTIFY4_EVENT_QUEUE_SIZE) {
> +			/* We're generating notifications too fast. Recall. */
> +			spin_unlock(&ncn->ncn_lock);
> +			nfsd_break_deleg_cb(fl);
> +			continue;
> +		}
> +		ncn->ncn_evt[ncn->ncn_evt_cnt++] = nfsd_notify_event_get(evt);

The above nfsd_notify_event_get() causes a refcount leak. Fixed in
tree.
-- 
Jeff Layton <jlayton@...nel.org>