Re: [PATCH 2/4] fsnotify: count s_fsnotify_inode_refs for attached connectors

[Matthew Bobrowski <repnop@google.com>]

On Tue, Aug 03, 2021 at 09:03:42PM +0300, Amir Goldstein wrote:
> Instead of incrementing s_fsnotify_inode_refs when detaching connector
> from inode, increment it earlier when attaching connector to inode.
> Next patch is going to use s_fsnotify_inode_refs to count all objects
> with attached connectors.
> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>

LGTM.

Reviewed-by: Matthew Bobrowski <repnop@google.com>

> ---
>  fs/notify/mark.c | 29 ++++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/notify/mark.c b/fs/notify/mark.c
> index 80459db58f63..2d8c46e1167d 100644
> --- a/fs/notify/mark.c
> +++ b/fs/notify/mark.c
> @@ -169,6 +169,21 @@ static void fsnotify_connector_destroy_workfn(struct work_struct *work)
>  	}
>  }
>  
> +static void fsnotify_get_inode_ref(struct inode *inode)
> +{
> +	ihold(inode);
> +	atomic_long_inc(&inode->i_sb->s_fsnotify_inode_refs);
> +}
> +
> +static void fsnotify_put_inode_ref(struct inode *inode)
> +{
> +	struct super_block *sb = inode->i_sb;
> +
> +	iput(inode);
> +	if (atomic_long_dec_and_test(&sb->s_fsnotify_inode_refs))
> +		wake_up_var(&sb->s_fsnotify_inode_refs);
> +}
> +
>  static void *fsnotify_detach_connector_from_object(
>  					struct fsnotify_mark_connector *conn,
>  					unsigned int *type)
> @@ -182,7 +197,6 @@ static void *fsnotify_detach_connector_from_object(
>  	if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
>  		inode = fsnotify_conn_inode(conn);
>  		inode->i_fsnotify_mask = 0;
> -		atomic_long_inc(&inode->i_sb->s_fsnotify_inode_refs);
>  	} else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
>  		fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0;
>  	} else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) {
> @@ -209,19 +223,12 @@ static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark)
>  /* Drop object reference originally held by a connector */
>  static void fsnotify_drop_object(unsigned int type, void *objp)
>  {
> -	struct inode *inode;
> -	struct super_block *sb;
> -
>  	if (!objp)
>  		return;
>  	/* Currently only inode references are passed to be dropped */
>  	if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE))
>  		return;
> -	inode = objp;
> -	sb = inode->i_sb;
> -	iput(inode);
> -	if (atomic_long_dec_and_test(&sb->s_fsnotify_inode_refs))
> -		wake_up_var(&sb->s_fsnotify_inode_refs);
> +	fsnotify_put_inode_ref(objp);
>  }
>  
>  void fsnotify_put_mark(struct fsnotify_mark *mark)
> @@ -495,7 +502,7 @@ static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
>  	}
>  	if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
>  		inode = fsnotify_conn_inode(conn);
> -		ihold(inode);
> +		fsnotify_get_inode_ref(inode);
>  	}
>  
>  	/*
> @@ -505,7 +512,7 @@ static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
>  	if (cmpxchg(connp, NULL, conn)) {
>  		/* Someone else created list structure for us */
>  		if (inode)
> -			iput(inode);
> +			fsnotify_put_inode_ref(inode);
>  		kmem_cache_free(fsnotify_mark_connector_cachep, conn);
>  	}
>  
> -- 
> 2.25.1
> 
/M