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Date: Wed, 16 Jun 2021 10:49:10 +0300 From: Amir Goldstein <amir73il@...il.com> To: Gabriel Krisman Bertazi <krisman@...labora.com> Cc: kernel@...labora.com, "Darrick J. Wong" <djwong@...nel.org>, Theodore Tso <tytso@....edu>, Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.com>, David Howells <dhowells@...hat.com>, Khazhismel Kumykov <khazhy@...gle.com>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Ext4 <linux-ext4@...r.kernel.org> Subject: Re: [PATCH v2 01/14] fsnotify: Don't call insert hook for overflow events On Wed, Jun 16, 2021 at 2:56 AM Gabriel Krisman Bertazi <krisman@...labora.com> wrote: > > Overflow events are not mergeable, so they are not hashed_events. 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. > > Avoid calling the insert hook when adding an overflow event. > > Fixes: 94e00d28a680 ("fsnotify: use hash table for faster events merge") > Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com> > --- > fs/notify/notification.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/fs/notify/notification.c b/fs/notify/notification.c > index 32f45543b9c6..033294669e07 100644 > --- a/fs/notify/notification.c > +++ b/fs/notify/notification.c > @@ -106,6 +106,11 @@ int fsnotify_add_event(struct fsnotify_group *group, > return ret; > } > event = group->overflow_event; > + /* > + * Since overflow events are not mergeable, don't insert > + * them in the merge hash. > + */ > + insert = NULL; > goto queue; > } > Hmm, the fix looks correct, but a bit fragile. While it makes sense that @insert is the counterpart of @merge there is nothing in the API that mandates it. Therefore, it would be more robust IMO to add a check fanotify_is_hashed_event(mask) in fanotify_insert_event() to match fanotify_is_hashed_event(mask) in get_one_event(). If we do that, we can also simplify: --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -779,8 +779,7 @@ 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); Thanks, Amir.
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