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Date:   Thu, 27 Feb 2020 14:30:16 +0100
From:   Jan Kara <jack@suse.cz>
To:     Amir Goldstein <amir73il@gmail.com>
Cc:     Jan Kara <jack@suse.cz>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2 11/16] fanotify: prepare to encode both parent and
 child fid's
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On Thu 27-02-20 14:12:30, Amir Goldstein wrote:
> >
> > > struct fanotify_fh_name {
> > >          union {
> > >                 struct {
> > >                        u8 fh_type;
> > >                        u8 fh_len;
> > >                        u8 name_len;
> > >                        u32 hash;
> > >                 };
> > >                 u64 hash_len;
> > >         };
> > >         union {
> > >                 unsigned char fh[FANOTIFY_INLINE_FH_LEN];
> > >                 unsigned char *ext_fh;
> > >         };
> > >         char name[0];
> > > };
> >
> > So based on the above I wouldn't add just name hash to fanotify_fh_name at
> > this point...
> >
> 
> OK. but what do you think about tying name with fh as above?
> At least name_len gets to use the hole this way.

Is saving that one byte for name_len really worth the packing? If anything,
I'd rather do the fanotity_fh padding optimization I outlined in another
email. That would save one long without any packing and the following u8
name_len would get packed tightly after the fanotify_fh by the compiler.

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