linux-ext4 - Re: [PATCH v3 01/15] fsnotify: Don't insert unmergeable events in hashtable

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Date:   Wed, 7 Jul 2021 21:21:04 +0200
From:   Jan Kara <jack@...e.cz>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     amir73il@...il.com, djwong@...nel.org, tytso@....edu,
        david@...morbit.com, jack@...e.com, dhowells@...hat.com,
        khazhy@...gle.com, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH v3 01/15] fsnotify: Don't insert unmergeable events in
 hashtable

On Tue 29-06-21 15:10:21, Gabriel Krisman Bertazi wrote:
> Some events, like the overflow event, are not mergeable, so they are not
> hashed.  But, when failing inside fsnotify_add_event for lack of space,
> fsnotify_add_event() still calls the insert hook, which adds the
> overflow event to the merge list.  Add a check to prevent any kind of
> unmergeable event to be inserted in the hashtable.
> 
> Fixes: 94e00d28a680 ("fsnotify: use hash table for faster events merge")
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>

Looks good. Feel free to add:

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

								Honza

> 
> ---
> Changes since v2:
>   - Do check for hashed events inside the insert hook (Amir)
> ---
>  fs/notify/fanotify/fanotify.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index 057abd2cf887..310246f8d3f1 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -702,6 +702,9 @@ static void fanotify_insert_event(struct fsnotify_group *group,
>  
>  	assert_spin_locked(&group->notification_lock);
>  
> +	if (!fanotify_is_hashed_event(event->mask))
> +		return;
> +
>  	pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
>  		 group, event, bucket);
>  
> @@ -779,8 +782,7 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
>  
>  	fsn_event = &event->fse;
>  	ret = fsnotify_add_event(group, fsn_event, fanotify_merge,
> -				 fanotify_is_hashed_event(mask) ?
> -				 fanotify_insert_event : NULL);
> +				 fanotify_insert_event);
>  	if (ret) {
>  		/* Permission events shouldn't be merged */
>  		BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
> -- 
> 2.32.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR