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Date:   Thu, 5 Aug 2021 11:14:07 +0200
From:   Jan Kara <jack@suse.cz>
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     jack@suse.com, amir73il@gmail.com, djwong@kernel.org,
        tytso@mit.edu, david@fromorbit.com, dhowells@redhat.com,
        khazhy@google.com, linux-fsdevel@vger.kernel.org,
        linux-ext4@vger.kernel.org, linux-api@vger.kernel.org,
        kernel@collabora.com
Subject: Re: [PATCH v5 04/23] fsnotify: Reserve mark bits for backends
Message-ID: <20210805091407.GB14483@quack2.suse.cz>
References: <20210804160612.3575505-1-krisman@collabora.com>
 <20210804160612.3575505-5-krisman@collabora.com>
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On Wed 04-08-21 12:05:53, Gabriel Krisman Bertazi wrote:
> Split out the final bits of struct fsnotify_mark->flags for use by a
> backend.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> ---
>  include/linux/fsnotify_backend.h | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index 1ce66748a2d2..9d5586445c65 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -363,6 +363,21 @@ struct fsnotify_mark_connector {
>  	struct hlist_head list;
>  };
>  
> +#define FSNOTIFY_MARK_FLAG(flag)	\
> +static const unsigned int FSNOTIFY_MARK_FLAG_##flag = \
> +	(1 << FSN_MARK_FL_BIT_##flag)

Static variable declaration in a header file makes me a bit uneasy. I know
it is const so a compiler should optimize this to a constant but still
there will likely be some side-effects (see the 0-day warning).

Honestly, given these are just three flags I'd just don't overengineer this
and have:

#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY \
			(1 << FSN_MARK_FL_BIT_IGNORED_SURV_MODIFY)
...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR