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Tue, 21 May 2024 11:36:44 +0000 (GMT) Received: from epsmgms1p2new.samsung.com (unknown [182.195.42.42]) by epsmtrp2.samsung.com (KnoxPortal) with ESMTP id 20240521113644epsmtrp264154696bb143f8efc50b183487f8be0~RffB3y50X0882408824epsmtrp20; Tue, 21 May 2024 11:36:44 +0000 (GMT) X-AuditID: b6c32a49-f53fa700000025c2-46-664c9cbb21d8 Received: from epsmtip2.samsung.com ( [182.195.34.31]) by epsmgms1p2new.samsung.com (Symantec Messaging Gateway) with SMTP id 66.AF.08390.C478C466; Tue, 21 May 2024 20:36:44 +0900 (KST) Received: from green245 (unknown [107.99.41.245]) by epsmtip2.samsung.com (KnoxPortal) with ESMTPA id 20240521113640epsmtip2581da03f3a550f38dd151415706754e9~Rfe_OwQgG1086110861epsmtip2B; Tue, 21 May 2024 11:36:40 +0000 (GMT) Date: Tue, 21 May 2024 16:59:42 +0530 From: Nitesh Shetty To: Hannes Reinecke Cc: Jens Axboe , Jonathan Corbet , Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Keith Busch , Christoph Hellwig , Sagi Grimberg , Chaitanya Kulkarni , Alexander Viro , Christian Brauner , Jan Kara , martin.petersen@oracle.com, bvanassche@acm.org, david@fromorbit.com, damien.lemoal@opensource.wdc.com, anuj20.g@samsung.com, joshi.k@samsung.com, nitheshshetty@gmail.com, gost.dev@samsung.com, Vincent Fu , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, dm-devel@lists.linux.dev, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v20 04/12] block: add emulation for copy Message-ID: <20240521112942.f23aael3qehi4gww@green245> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: User-Agent: NeoMutt/20171215 X-Brightmail-Tracker: H4sIAAAAAAAAA01TezBcZxT33bvuLtOVazE+guimnUTEYxO2n9SjUya9Bo2ZzLQNTXWH6zHW 7nbXIzE19ah6ZKzH5mUjraiWoMQjSjyarghWlVRIV0oy8RhliEeSFrWptWTy3+/8vt/vnPOd M4eFc5qZ1qwYUTwtFQmEXMKY0dzl4ODUVhIY6VqwZIvq1HdxlF6wiaPq8XwCzXetAHRxaQ1H U7ezANoYGMRR090JgErLrjKQ5nYrhtrLijB0vbobQ1cuZWCo++UCgYpUowBNjygx1DHmiK59 U85A7R19DDR8q4RA3/04zUQVPVoMFWaPYKhlKg2g2vmnDNQ7thdNnssGaHCzx/A9G2r4fgCl LoNUq3KcSQ1O1DOo4YEEqqEqh6Aay7+iZhuLAdWmSSWo7+UKQyovY5GgWjMfGVLL02MM6mnn CEHJm6oA9VvpHWawWUisZzQtiKCl9rQoXBwRI4ry4gacDPMNc+e78px4Hugdrr1IEEd7cf0C g52Oxwi3JsS1TxQIE7aoYIFMxnXx9pSKE+Jp+2ixLN6LS0sihBI3ibNMECdLEEU5i+j4YzxX 1yPuW8LPY6OfKRS4ZIU8s/ZMwUgFV0xygRELkm7wz5liIhcYszhkG4DrqfWYPlgB8OHQBtCp OOQLAFtnXznU5y7uiDoAfNQ4sBPMAPjTrAbTqRjk2zC3P5uZC1gsgnSE/S9ZOtqc5MLlLBVT p8fJ3wmoqWjarmBGekJtxZNtzCb5UK44z9RjU9hXPMXQ5TEi34XDqx/qaAvSBl7+4TmuywPJ CSNYsdBJ6Lvzg/eqd7EZnOtpYuqxNVxd7Njhk+D185WE3vw1gMoHSqB/8IGZ6nxch3EyGs6u lOJ63hZeUNdiet4E5m1MYXqeDVu+3cX7YU1d6U4BKzj6TxqhaxqSFCysCdUPaBHA2aJsZgHY p3ztb8rXyunxMZizlG6o3LLj5F5YoWXpoQOsu+VSCgyrgBUtkcVF0TJ3CU9EJ71aeLg4rgFs H9Ah/xYw/njJWQUwFlAByMK55uyGJv9IDjtCcDaZlorDpAlCWqYC7lu7KsStLcLFWxcoig/j uXm4uvH5fDePo3we15I9n3k1gkNGCeLpWJqW0NJdH8Yysk7FYo7u37zz5OSnv9jUlsRqQrRx gkitKvig7VJe/yXtvsS1DxbfsGIP7UkKlf83Y/AgJsgxXzqigZV2g6PPB1bvvdnnNff3xycs T7mY/So+m2LCyfGWj5oW35BXlR/2+cLloLzd0umvwMqaM1KxhVGEMcuA/yWOi5M37dZH/MW8 zy505uKJ5ZM32el7hKcOzI5HfTLeHNrX2UPdNAsJTgujsxcyFadfaPqvLXdYdJ1Qd8OaoAPF FaNqXpbv4Q1nk8eqI3O8P9LzMjhFgpSw6p/HeydTmEGJ7cLkaFdT7Ud19x8OuXfHWq//62Pg m1Ps5w3fUklu9HofL7ftqw+wu/y++emBIi5DFi3gHcKlMsH/dMWR5MkEAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrOIsWRmVeSWpSXmKPExsWy7bCSvK5Pu0+awYxf6hbrTx1jtmia8JfZ YvXdfjaL14c/MVpM+/CT2eLJgXZGi99nzzNbbDl2j9FiwaK5LBY3D+xkstizaBKTxcrVR5ks Zk9vZrI4+v8tm8WkQ9cYLZ5encVksfeWtsXCtiUsFnv2nmSxuLxrDpvF/GVP2S2WH//HZDGx 4yqTxY4njYwW616/Z7E4cUva4nF3B6PF+b/HWR1kPC5f8fY4tUjCY+esu+we5+9tZPG4fLbU Y9OqTjaPzUvqPV5snsnosftmA5vH4r7JrB69ze/YPHa23mf1+Pj0FovH+31X2Tz6tqxi9Diz 4Ah7gHAUl01Kak5mWWqRvl0CV8aUxq/sBUv4Kg5tKG9gfM7dxcjJISFgInGqexpTFyMXh5DA bkaJVVc/sEAkJCWW/T3CDGELS6z895wdougJo8T0V2vYQRIsAqoSXac7gGwODjYBbYnT/zlA wiICShIf2w+B1TMLXGKTWL5wN9ggYQEbiX/LHzGC2LwCZhJ9k6dADX3HKNF8ZjsrREJQ4uTM J2BXMAMVzdv8kBlkAbOAtMTyfxwgJqeAtcTlz34gFaICMhIzln5lnsAoOAtJ8ywkzbMQmhcw Mq9ilEwtKM5Nzy02LDDKSy3XK07MLS7NS9dLzs/dxAhOG1paOxj3rPqgd4iRiYPxEKMEB7OS CO+mLZ5pQrwpiZVVqUX58UWlOanFhxilOViUxHm/ve5NERJITyxJzU5NLUgtgskycXBKNTCV +51k8X2sq169+fjktuiPcRIfOu96K9Qejnr0yG+ZI9/N1MgDEtcXXXApTZmxs+7TV36RzyGz Q0L+BE+I/NIzaa6Au3GGSNTich6Lg1Pedl5dJTx9p8yLXD33niC5Dz+Tsy1DytvK9bpsdr/f 0KClNanQNMt6f47bn9kb9TyFJogU+M0q+DCl8cH5w20vWVMjUzTXr616qFPZ3+8YZF6p+NKW v2HeZv5lxVOYGZSdfWsfB1Uanjy29ULul2fzIysFE0x4mNbN2lbTXfLBefHz2Yf1A4Qfzw7c 1bR8aVWJTVv20/Ul8mkLb8S9mPmHjXP6J042xrozYXv/X8zSjHtX4PxEdpml8lwt39+H05VY ijMSDbWYi4oTAVGa+qWKAwAA X-CMS-MailID: 20240521113644epcas5p49bfa818b6040f17bad23f24e303ad269 X-Msg-Generator: CA Content-Type: multipart/mixed; boundary="----atUsqPFm-1W_PDIhMRaVeMNpJ8wr1jcbO3GdUizRktR65zpR=_159f3_" X-Sendblock-Type: REQ_APPROVE CMS-TYPE: 105P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20240520102906epcas5p15b5a0b3c8edd0bf3073030a792a328bb References: <20240520102033.9361-1-nj.shetty@samsung.com> <20240520102033.9361-5-nj.shetty@samsung.com> ------atUsqPFm-1W_PDIhMRaVeMNpJ8wr1jcbO3GdUizRktR65zpR=_159f3_ Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Disposition: inline On 21/05/24 09:06AM, Hannes Reinecke wrote: >On 5/20/24 12:20, Nitesh Shetty wrote: >>For the devices which does not support copy, copy emulation is added. >>It is required for in-kernel users like fabrics, where file descriptor is >>not available and hence they can't use copy_file_range. >>Copy-emulation is implemented by reading from source into memory and >>writing to the corresponding destination. >>At present in kernel user of emulation is fabrics. >> >>Signed-off-by: Nitesh Shetty >>Signed-off-by: Vincent Fu >>Signed-off-by: Anuj Gupta >>--- >> block/blk-lib.c | 223 +++++++++++++++++++++++++++++++++++++++++ >> include/linux/blkdev.h | 4 + >> 2 files changed, 227 insertions(+) >> >Again, I'm not sure if we need this. >After all, copy offload _is_optional, so we need to be prepared to >handle systems where it's not supported. In the end, the caller might >decide to do something else entirely; having an in-kernel emulation >would defeat that. >And with adding an emulation to nullblk we already have an emulation >target to try if people will want to start experimenting. >So I'd rather not have this but rather let the caller deal with the >fact that copy offload is optional. > Unlike previous iteration, blkdev_copy_offload doesn't fallback to emulation incase offload fails. This is one more option caller/user can leverage, if for some reason device copy offload is not supported/optimal. It is upto to the caller to decide, if it wants to use copy emulation. Moreover we found this is very useful for fabrics scenario, where this saves the network bandwidth, by sending offload over the network rather than read+write(when target doesn't support offload). Thank you Nitesh Shetty ------atUsqPFm-1W_PDIhMRaVeMNpJ8wr1jcbO3GdUizRktR65zpR=_159f3_ Content-Type: text/plain; charset="utf-8" ------atUsqPFm-1W_PDIhMRaVeMNpJ8wr1jcbO3GdUizRktR65zpR=_159f3_--