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Tue, 13 Apr 2021 11:35:10 +0000 (GMT) From: Changheun Lee To: gregkh@linuxfoundation.org Cc: Johannes.Thumshirn@wdc.com, asml.silence@gmail.com, axboe@kernel.dk, bvanassche@acm.org, damien.lemoal@wdc.com, hch@infradead.org, jisoo2146.oh@samsung.com, junho89.kim@samsung.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ming.lei@redhat.com, mj0123.lee@samsung.com, nanich.lee@samsung.com, osandov@fb.com, patchwork-bot@kernel.org, seunghwan.hyun@samsung.com, sookwan7.kim@samsung.com, tj@kernel.org, tom.leiming@gmail.com, woosung2.lee@samsung.com, yt0928.kim@samsung.com Subject: Re: [PATCH v7 3/3] bio: add limit_bio_size sysfs Date: Tue, 13 Apr 2021 20:17:27 +0900 Message-Id: <20210413111727.12999-1-nanich.lee@samsung.com> X-Mailer: git-send-email 2.29.0 In-Reply-To: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrEJsWRmVeSWpSXmKPExsWy7bCmvu77xtIEgzMnZCzmrNrGaLH6bj+b xbQPP5ktWtu/MVk0L17PZnF6wiImi54nTawWf7vuMVl8fVhssfeWtsXlXXPYLA5NbmaymL55 DrPFtftn2C0O37vKYvFwyURmi3MnP7FazHvsYPFr+VFGi/c/rrNbnNoxmdli/d6fbA5iHpev eHtMbH7H7rFz1l12j80rtDwuny312LSqk81j/9w17B7v911l8+jbsorR4/MmOY/2A91MAdxR OTYZqYkpqUUKqXnJ+SmZeem2St7B8c7xpmYGhrqGlhbmSgp5ibmptkouPgG6bpk5QJ8qKZQl 5pQChQISi4uV9O1sivJLS1IVMvKLS2yVUgtScgoMDQr0ihNzi0vz0vWS83OtDA0MjEyBKhNy MuYf7WQu6Oet+L3jH3sDYx9XFyMHh4SAiURTQ2UXIxeHkMAORolNmycyQTifGCV+vvvPAuF8 ZpTonXyctYuRE6xj0pIZUIldjBKr9l5jhqtqeL2NBaSKTUBHou/tLTYQW0RATuLJ7T9gRcwC /5glFvf8YQRJCAtYSizr3g02lkVAVaLx4F6wBl4Ba4l505czQayTl/hzv4cZxOYU0JT4tPks E0SNoMTJmU/AljED1TRvnQ22QEKgmVNi25yPbBDNLhKHjixigbCFJV4d38IOYUtJvOxvY4do 6GaUaG6bzwjhTGCUWPJ8GdRqY4lPnz8zgsKJGWj1+l36EGFFiZ2/5zJCbOaTePe1hxUSlLwS HW1CECUqEmda7jPD7Hq+difURA+J69fvgj0sJFAjcf5sJ/sERoVZSP6ZheSfWQiLFzAyr2IU Sy0ozk1PLTYsMEWO402M4MSvZbmDcfrbD3qHGJk4GA8xSnAwK4nwuk0pSRDiTUmsrEotyo8v Ks1JLT7EaAoM7YnMUqLJ+cDck1cSb2hqZGxsbGFiZm5maqwkzptk8CBeSCA9sSQ1OzW1ILUI po+Jg1OqgWnb5UU26blhJnnKBv6N2tHZTptZsyb/ULkhUqJtZHLUnu+lj11MZot2rvqUmi/O mmq33VdFJnVw/f7PqtT+lT2hoILHzJ/r7Nw7eozbe6a7Pl3wb0+GEL+Py3d5V4cJs6UkO8Ie /Nshtz6+LY9bsUeAwTpzoQ3fBGn9q3/3P35oZn0j/IRb2nqmq/PWXxA+/ets0XQD6YdzpcOr 0veHq4R/P2XeaMSw+sBEC+W1a7gTtSRLJDWyn/NLbnbaavrR1e+SI6tCYoj7/PRve4sbOv2q f3ndLD5UEW/Pb3CA9bTOJKa/11vr37glBrZGv+012Hcupmb1h8MLuzsdp6dJNbaHa347+WLv 6u44SWYlluKMREMt5qLiRAAsWXKahQQAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrFIsWRmVeSWpSXmKPExsWy7bCSvO67xtIEg9d3TS3mrNrGaLH6bj+b xbQPP5ktWtu/MVk0L17PZnF6wiImi54nTawWf7vuMVl8fVhssfeWtsXlXXPYLA5NbmaymL55 DrPFtftn2C0O37vKYvFwyURmi3MnP7FazHvsYPFr+VFGi/c/rrNbnNoxmdli/d6fbA5iHpev eHtMbH7H7rFz1l12j80rtDwuny312LSqk81j/9w17B7v911l8+jbsorR4/MmOY/2A91MAdxR XDYpqTmZZalF+nYJXBnzj3YyF/TzVvze8Y+9gbGPq4uRk0NCwERi0pIZLF2MXBxCAjsYJdpa brNBJKQkjp94y9rFyAFkC0scPlwMUfORUWLm5u0sIDVsAjoSfW9vgdWLCMhJPLn9hxmkiFlg BotE7/c9jCAJYQFLiWXdu1lBbBYBVYnGg3vBGngFrCXmTV/OBLFMXuLP/R5mEJtTQFPi0+az YHEhAQ2JM0uPsULUC0qcnPkEbDEzUH3z1tnMExgFZiFJzUKSWsDItIpRMrWgODc9t9iwwCgv tVyvODG3uDQvXS85P3cTIzg6tbR2MO5Z9UHvECMTB+MhRgkOZiURXrcpJQlCvCmJlVWpRfnx RaU5qcWHGKU5WJTEeS90nYwXEkhPLEnNTk0tSC2CyTJxcEo1MPGUn+wXkeN/UHjp7p+5dQst nAJbg89N4z9QaG2T4P3q7BYxvw2BG6c03J1hyTH1WskcIx/zLStebgqtipv//brAv7LDG548 E/9w/fWhQ18UXr851WJ74WLCFD9R05pdDM5aJy3EUxZqsh3jbv9Q+rzyk+GiE7fXP9usFLD+ 2cr767dEGeX/3xDmlRW/w95yxqdL625bRfV0yz5iKv2uXm526IXbxec7xdYwm/01XM7+62jJ 7CObGC5JTSwK7FwS8SpWKelXB7+Gz+2Q0lUlslvY759Ukeb+XbNi4d4+yYuLf3k8F5q39xBH xe3HLUKiLOeaj7/4ZVy3x6FXJkPSf++LLZPnaDeddGHbujSqPGuTEktxRqKhFnNRcSIAhRGb 6T0DAAA= X-CMS-MailID: 20210413113510epcas1p29dd90b47ba8c8701a2309fc34698ad29 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20210413113510epcas1p29dd90b47ba8c8701a2309fc34698ad29 References: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org > On Tue, Apr 13, 2021 at 11:55:02AM +0900, Changheun Lee wrote: > > Add limit_bio_size block sysfs node to limit bio size. > > Queue flag QUEUE_FLAG_LIMIT_BIO_SIZE will be set if limit_bio_size is set. > > And bio max size will be limited by queue max sectors via > > QUEUE_FLAG_LIMIT_BIO_SIZE set. > > > > Signed-off-by: Changheun Lee > > --- > > Documentation/ABI/testing/sysfs-block | 10 ++++++++++ > > Documentation/block/queue-sysfs.rst | 7 +++++++ > > block/blk-sysfs.c | 3 +++ > > 3 files changed, 20 insertions(+) > > Isn't it too late to change the sysfs entry after the device has been > probed and initialized by the kernel as the kernel does not look at this > value after that? Kernel will take a look this when page is merged to bio. And bio size will be limited dynamically. > > Why do you need a userspace knob for this? What tool is going to ever > change this, and what logic is it going to use to change it? Why can't > the kernel also just "do the right thing" and properly detect this > option as well as userspace can? Actually I didn't considerate userspace knob at first. And there is no tool, no logic to change it. It's a kind of policy about bio max size. One time setting will be OK on system boot time actually. At the first, I suggested 1MB bio max size. It is same with bio max size before applying of multipage bvec. But there are requests of big bio size on another system environment, and feedback of knob for utility too. So I made this as a optional for each system, and a knob too. > > thanks, > > greg k-h Thanks, Changheun Lee