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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1744306710; bh=YwxaJTg4VJbIYIQ6s+Ic7Nv7sEsm9q3MKFC0yNU64hU=; h=Date:From:To:Cc:Subject:Content-Type; b=MgKhBiI69HXrwf01/pCiEXtBE6JBwR9Y1Z5yfP3KyiTkwq2mmN5P0NyW2pRhAY1qq YRo6dPXEpIV72q3digPVEezjwF3sCVOkocRnQhlUZDLEhOrpKaPERGmzF8eTUVZoDL dZNPOCb2vetDceHq1sYqwupZIBXk5U/E1d6DiY6XtTn3V+jLKkVGfLkkWtC15L3AQi JFG4NetVjuKrUx2mY0vEEXoJL4YfT6UIjj6lwkQA1KcW1wZ//zKsSfUH78sogpbkYD S8CgcAdfyPBa7PH6fK1a7gEMXpPOIspd6R0zwok7cIml0IyPtZhMClXoHw3losIOZ9 LUW8qJUc51SIA== Date: Thu, 10 Apr 2025 10:38:17 -0700 From: Davidlohr Bueso To: Jan Kara Cc: Luis Chamberlain , brauner@kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, riel@surriel.com, willy@infradead.org, hannes@cmpxchg.org, oliver.sang@intel.com, david@redhat.com, axboe@kernel.dk, hare@suse.de, david@fromorbit.com, djwong@kernel.org, ritesh.list@gmail.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com Subject: Re: [PATCH v2 2/8] fs/buffer: try to use folio lock for pagecache lookups Message-ID: <20250410173817.5cdlnnooxwgbkpov@offworld> Mail-Followup-To: Jan Kara , Luis Chamberlain , brauner@kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, riel@surriel.com, willy@infradead.org, hannes@cmpxchg.org, oliver.sang@intel.com, david@redhat.com, axboe@kernel.dk, hare@suse.de, david@fromorbit.com, djwong@kernel.org, ritesh.list@gmail.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com References: <20250410014945.2140781-1-mcgrof@kernel.org> <20250410014945.2140781-3-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20220429 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 345AC20009 X-Stat-Signature: h697rij1yfehnk5n7tzm3zbjxd4y3zmp X-Rspam-User: X-HE-Tag: 1744306845-779483 X-HE-Meta: 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 MHfi/Tm+ 0LXOGRuvLh2VpKYc/7vni6IsNS4T4CLeeOem3CfVV1FHXLBt7vX8PY1gVMlG22h83znIuAYkI9qp4MDbVUICsC+xIhe8BseW1kO+z5wSq8DG71UUc5miTcGJRctFyit43G/2yFU7ZIEsWNhhNobOnkBrfkSPDBwXjz8c8ExR+bZUDnoFXS+Tu/27RmcQ5Ovj9uuwWaBA5cZ5grZU6yebRADSh6xCy0o+9HXb01DVnz7K8rqBCh0MIC8dLCL6OiYEqT6kqwdN3+o7zD49mwAzeWygCbqqEidJv/7J9TVgGRDxf5w7cPsDBrQD4VexGG4Gxm60Z44ULpdK19Q7pHKHPV3WY7ZixgNjqE0yIER/TH+bCpOI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000736, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 10 Apr 2025, Jan Kara wrote: >I'd rather do: > > if (atomic) { > spin_lock(&bd_mapping->i_private_lock); > folio_locked = false; > } else { > folio_lock(folio); > } > Fine with me. I just think the trylock for the atomic scenario would have given greater chances of successful migration, but at a lack of determinism, of course. >I'd actually love to do something like: > > if (atomic) { > if (!folio_trylock(folio)) > bail... > } else { > folio_lock(folio); > } > >but that may be just too radical this point and would need some serious >testing how frequent the trylock failures are. No point in blocking this >series with it. So just go with the deterministic use of i_private_lock for >atomic users for now. This acually crossed my mind, but I also considered the scheme a little too much for this series.