From mboxrd@z Thu Jan 1 00:00:00 1970 From: jack@suse.cz (Jan Kara) Date: Thu, 24 Jan 2019 09:35:36 +0100 Subject: [PATCH 2/4] introduce four macros for in-kernel hints In-Reply-To: References: <1547047861-7271-1-git-send-email-joshi.k@samsung.com> <1547047861-7271-3-git-send-email-joshi.k@samsung.com> Message-ID: <20190124083536.GB12184@quack2.suse.cz> On Wed 23-01-19 19:27:12, Javier Gonz?lez wrote: > > > On 9 Jan 2019,@16.30, Kanchan Joshi wrote: > > > > Exiting write-hints are exposed to user-mode. There is a possiblity > > of conflict if kernel happens to use those. This patch introduces four > > write-hints for exclusive kernel-mode use. > > > > Signed-off-by: Kanchan Joshi > > --- > > include/linux/fs.h | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index 811c777..e8548eb 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -291,6 +291,11 @@ enum rw_hint { > > WRITE_LIFE_MEDIUM = RWH_WRITE_LIFE_MEDIUM, > > WRITE_LIFE_LONG = RWH_WRITE_LIFE_LONG, > > WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME, > > +/* below ones are meant for in-kernel use */ > > + KERN_WRITE_LIFE_SHORT, > > + KERN_WRITE_LIFE_MEDIUM, > > + KERN_WRITE_LIFE_LONG, > > + KERN_WRITE_LIFE_EXTREME > > }; > > > > I think Jens and Dave meant kernel hints to go top down. This would also > give space for supporting more hints / streams from both ends for user > and kernel. Yes, that was the idea however if I understand it right, the write hints do not really have to be consistent boot-to-boot since they aren't stored persistently by the disk, are they? If that's the case, it doesn't really matter which numbers we pick. One thing I don't quite like is the naming of KERN_WRITE_LIFE_SHORT etc.. It is upto filesystem to assign meanings to the write hints. So I think it is enough to provide something like KERN_WRITE_HINT_MIN which is the first hint available to the kernel and then the number of hints available to the kernel. Honza -- Jan Kara SUSE Labs, CR