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Wong" , Dave Chinner , Theodore Ts'o , Andreas Dilger , Chris Mason , Josef Bacik , David Sterba , Hugh Dickins , Andrew Morton , Amir Goldstein , Jan Kara , David Howells , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH RFC 2/9] timekeeping: new interfaces for multigrain timestamp handing Message-ID: <20231019-fluor-skifahren-ec74ceb6c63e@brauner> References: <20231018-mgtime-v1-0-4a7a97b1f482@kernel.org> <20231018-mgtime-v1-2-4a7a97b1f482@kernel.org> <5f96e69d438ab96099bb67d16b77583c99911caa.camel@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5f96e69d438ab96099bb67d16b77583c99911caa.camel@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 384B31C000A X-Stat-Signature: bzbmfhhkbd3c9jhw4rk48yb55je13au9 X-HE-Tag: 1697707763-286315 X-HE-Meta: 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 508GyI2D NAonPbF58fyB/lJgD8wBh93UUWZDbeWOeKzvKn4ktKCZGvAMSDvWzxA4WQXVP4qplkGcXaJpGpeTVHmiGGYlNujnPDhg68+PJDZLpH+5/SDzzZmEFRj6jTBp25wTcyZQEHkeWA4Rmt5dipCb1QFUIldhyYCsKu1IHp6hD5lOBRL+Oy0A7LQjVotvKcCX+8EnZuKJH X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > Back to your earlier point though: > > Is a global offset really a non-starter? I can see about doing something > per-superblock, but ktime_get_mg_coarse_ts64 should be roughly as cheap > as ktime_get_coarse_ts64. I don't see the downside there for the non- > multigrain filesystems to call that. I have to say that this doesn't excite me. This whole thing feels a bit hackish. I think that a change version is the way more sane way to go. > > On another note: maybe I need to put this behind a Kconfig option > initially too? So can we for a second consider not introducing fine-grained timestamps at all. We let NFSv3 live with the cache problem it's been living with forever. And for NFSv4 we actually do introduce a proper i_version for all filesystems that matter to it. What filesystems exactly don't expose a proper i_version and what does prevent them from adding one or fixing it?