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Tue, 20 Apr 2021 01:11:39 +0000 (GMT) From: Changheun Lee To: bvanassche@acm.org Cc: Johannes.Thumshirn@wdc.com, asml.silence@gmail.com, axboe@kernel.dk, damien.lemoal@wdc.com, gregkh@linuxfoundation.org, 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 1/3] bio: limit bio max size Date: Tue, 20 Apr 2021 09:53:44 +0900 Message-Id: <20210420005344.9280-1-nanich.lee@samsung.com> X-Mailer: git-send-email 2.29.0 In-Reply-To: <918e0d57-ffbc-7dcd-6eba-87d22aceb9d6@acm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrAJsWRmVeSWpSXmKPExsWy7bCmga6PVl2CwbwvNhZzVm1jtFh9t5/N YtqHn8wWre3fmCyaF69nszg9YRGTRc+TJlaLv133mCy+Piy22HtL2+LyrjlsFocmNzNZTN88 h9ni2v0z7BaH711lsXi4ZCKzxbmTn1gt5j12sPi1/Cijxfsf19ktTu2YzGyxfu9PNgcxj8tX vD0mNr9j99g56y67x+YVWh6Xz5Z6bFrVyeaxf+4ado/3+66yefRtWcXo8XmTnEf7gW6mAO6o HJuM1MSU1CKF1Lzk/JTMvHRbJe/geOd4UzMDQ11DSwtzJYW8xNxUWyUXnwBdt8wcoE+VFMoS c0qBQgGJxcVK+nY2RfmlJakKGfnFJbZKqQUpOQWGBgV6xYm5xaV56XrJ+blWhgYGRqZAlQk5 GQ0vrzAV/BatmHnOroHxmWAXIweHhICJxIym8i5GLg4hgR2MEocvbGXqYuQEcj4xSsw9wgeR +Mwo0fhhGiNIAqRh37SXTBCJXYwS38/PY4Kr2rvhKQtIFZuAjkTf21tsILaIgJjE5S/fGEGK mAXaWCRutVwDSwgLGEts/7uQHeQOFgFViVtLZUDCvAJWEguPLGaH2CYv8ed+DzOIzSlgLbGn fy8bRI2gxMmZT8B2MQPVNG+dzQwyX0LgP4fE+WsfWSGaXSS+v9gCdbawxKvjW6CGSkl8fgcy CKShm1GiuW0+I4QzgVFiyfNlTBBVxhKfPn9mBLmOWUBTYv0ufYiwosTO33MZITbzSbz72sMK CUheiY42IYgSFYkzLfeZYXY9X7sTaqKHxNv2i4yQ0OpjlFi45SrzBEaFWUgemoXkoVkImxcw Mq9iFEstKM5NTy02LDBEjuFNjOCkr2W6g3Hi2w96hxiZOBgPMUpwMCuJ8N6vrUkQ4k1JrKxK LcqPLyrNSS0+xGgKDO2JzFKiyfnAvJNXEm9oamRsbGxhYmZuZmqsJM6b7lydICSQnliSmp2a WpBaBNPHxMEp1cAk66Djbzjjv6iG+trr9rua+52Dr/ow7BWMU9P83cRg8q94Uh7rbAOzyZpy BZfdEutPerVv9XXnV7knt3TLEz6/6jd2Lz6aJe3YOY83SI2jUF04/PHRnr/VrK8LDkV3uf0z X8Ixv+jXuVs7f8Qd96o23xpwU3K3jau2blu0M2PF2cds9+419dXvFruuHW6uvj416bGoU+/f jefu1T5/xzvLYv8SqYXbvi4LLPlsH/7uxvUzhfOT5+ukNMlypT+r3uvMe9t103sfscvZGds2 rp6XdqLJQz5ZouO03Kt/MRZiixb/rvond/jQs+kiSupWDjZMu0N7rAvkfHqnM3SefK55J8cu Ov1n9ttGBXuzdUosxRmJhlrMRcWJADMYBSuDBAAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrBIsWRmVeSWpSXmKPExsWy7bCSvK63Vl2CwY3HkhZzVm1jtFh9t5/N YtqHn8wWre3fmCyaF69nszg9YRGTRc+TJlaLv133mCy+Piy22HtL2+LyrjlsFocmNzNZTN88 h9ni2v0z7BaH711lsXi4ZCKzxbmTn1gt5j12sPi1/Cijxfsf19ktTu2YzGyxfu9PNgcxj8tX vD0mNr9j99g56y67x+YVWh6Xz5Z6bFrVyeaxf+4ado/3+66yefRtWcXo8XmTnEf7gW6mAO4o LpuU1JzMstQifbsEroyGl1eYCn6LVsw8Z9fA+Eywi5GTQ0LARGLftJdMXYxcHEICOxglFm+f wgSRkJI4fuItaxcjB5AtLHH4cDFEzUdGiR8HvzKC1LAJ6Ej0vb3FBmKLCIhJXP7yjRGkiFlg AYvEwZ0n2EESwgLGEtv/LmQHGcQioCpxa6kMSJhXwEpi4ZHF7BC75CX+3O9hBrE5Bawl9vTv BZspBFRz9uRNVoh6QYmTM5+wgNjMQPXNW2czT2AUmIUkNQtJagEj0ypGydSC4tz03GLDAqO8 1HK94sTc4tK8dL3k/NxNjODI1NLawbhn1Qe9Q4xMHIyHGCU4mJVEeO/X1iQI8aYkVlalFuXH F5XmpBYfYpTmYFES573QdTJeSCA9sSQ1OzW1ILUIJsvEwSnVwNQ0RZ/d+H+cZ+VxYZG7vKJ8 i+5fNxc4tnRCdFX6nfcWUbz3BKq7X8wN0mdknXtDd+mt1C7eMzmhf/I5mf7sjwys2ry65y6r GP/Fto9sWwQu/fp0Y2oQn9J8/+T1QRFiWRwZaVKa54IZHNnU1+zlM1z8cbvgwfAU7xtNAiGN sxc2dP4pqzc9fHXl8uVcy15wrufMCbjUyv9UkEWtUaq2yi2zTfTvBq9fbd08sVv8vLn8X2SH ld1SKrRNsPvimSGeeO7lO07B2Wn8klzMRjdOfXZwv7smOCHXfqbF58y8mQL1EoUpsQ/UGHrz zjxPs4k1NF5y4eS69uP+F7743X22N2zjieh9U2oi9ULWiSQosRRnJBpqMRcVJwIADyeTlTsD AAA= X-CMS-MailID: 20210420011139epcas1p429e791d6f8ffea596661e9366babbec8 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: 20210420011139epcas1p429e791d6f8ffea596661e9366babbec8 References: <918e0d57-ffbc-7dcd-6eba-87d22aceb9d6@acm.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On 4/18/21 10:49 PM, Changheun Lee wrote: > >>> @@ -167,6 +168,7 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto > >>> max_sectors = round_down(max_sectors, > >>> limits->logical_block_size >> SECTOR_SHIFT); > >>> limits->max_sectors = max_sectors; > >>> + limits->bio_max_bytes = max_sectors << SECTOR_SHIFT; > >>> > >>> q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9); > >>> } > >> > >> Can the new shift operation overflow? If so, how about using > >> check_shl_overflow()? > > > > Actually, overflow might be not heppen in case of physical device. > > But I modified as below. feedback about this. > > > > @@ -168,6 +169,9 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto > > limits->logical_block_size >> SECTOR_SHIFT); > > limits->max_sectors = max_sectors; > > > > + limits->bio_max_bytes = check_shl_overflow(max_sectors, SECTOR_SHIFT, > > + &limits->bio_max_bytes) ? UINT_MAX : max_sectors << SECTOR_SHIFT; > > + > > q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9); > > } > > EXPORT_SYMBOL(blk_queue_max_hw_sectors); > > If no overflow occurs, check_shl_overflow() stores the result in the > memory location the third argument points at. So the above expression > can be simplified into the following: > > if (check_shl_overflow(max_sectors, SECTOR_SHIFT, &limits->bio_max_bytes)) { > limits->bio_max_bytes = UINT_MAX; > } OK. No problem. It might be more readable. > > >>> diff --git a/include/linux/bio.h b/include/linux/bio.h > >>> index d0246c92a6e8..e5add63da3af 100644 > >>> --- a/include/linux/bio.h > >>> +++ b/include/linux/bio.h > >>> @@ -106,6 +106,8 @@ static inline void *bio_data(struct bio *bio) > >>> return NULL; > >>> } > >>> > >>> +extern unsigned int bio_max_size(struct bio *bio); > >> > >> You may want to define bio_max_size() as an inline function in bio.h > >> such that no additional function calls are introduced in the hot path. > > > > I tried, but it is not easy. because request_queue structure of blkdev.h > > should be referred in bio.h. I think it's not good to apply as a inline function. > > Please don't worry about this. Inlining bio_max_size() is not a big > concern to me. > > Thanks, > > Bart. I think removing of UINT_MAX setting in blk_stack_limits() might be good. Because default queue limits for stacking device will be set in blk_set_stacking_limits(), and blk_set_default_limits() will be called automatically. So setting of UINT_MAX in blk_stack_limits() is not needed. And setting in blk_stack_limits() can overwrite bio_max_bytes as a default after stacking driver set to proper bio_max_bytes value. Thanks, Changheun Lee.