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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Apr 2023 17:28:45.7818 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f27e3af2-80f9-439a-461a-08db428ddc70 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT097.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB7014 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Hi, When IO_URING_F_NONBLOCK is set on io_kiocb req->flag in io_write() or io_read() IOCB_NOWAIT is set for kiocb when passed it to the respective rw_iter callback. This sets REQ_NOWAIT for underlaying I/O. The result is low level driver always sees block layer request as REQ_NOWAIT even if user has submitted request with nowait = 0 e.g. fio nowait=0. That is not consistent behaviour with other fio ioengine such as libaio as it will issue non REQ_NOWAIT request with REQ_NOWAIT:- libaio nowait = 0:- null_blk: fio:null_handle_rq 1288 *NOWAIT=FALSE* REQ_OP_WRITE libaio nowait = 1:- null_blk: fio:null_handle_rq 1288 *NOWAIT=TRUE* REQ_OP_WRITE * Without this patch with fio ioengine io_uring :- --------------------------------------------------- iouring nowait = 0:- null_blk: fio:null_handle_rq 1288 *NOWAIT=TRUE* REQ_OP_WRITE iouring nowait = 1:- null_blk: fio:null_handle_rq 1288 *NOWAIT=TRUE* REQ_OP_WRITE * With this patch with fio ioengine io_uring :- --------------------------------------------------- iouring nowait = 0:- null_blk: fio:null_handle_rq 1307 *REQ_NOWAIT=FALSE* WRITE iouring nowait = 1: null_blk: fio:null_handle_rq 1307 *REQ_NOWAIT=TRUE* WRITE Instead of only relying on IO_URING_F_NONBLOCK blindly in io_read() and io_write(), also make sure io_kiocb->io_rw->flags is set to RWF_NOWAIT before we mark kiocb->ki_flags = IOCB_NOWAIT. Below is the deatailed testing log. -ck Chaitanya Kulkarni (1): io_uring: honor I/O nowait flag for read/write io_uring/rw.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) $ sh test-iouring-no-wait * Without this patch :- ####################### -------------------libaio nowait = 0-------------------------- ++ grep -e ioengine -e rw -e nowait fio/randwrite-libaio-nowait-0.fio ioengine=libaio rw=randwrite nowait=0 <----------------------------- overwrite=0 ++ fio fio/randwrite-libaio-nowait-0.fio --filename=/dev/nullb0 ++ grep err RANDWRITE: (groupid=0, jobs=1): err= 0: pid=40835: Thu Apr 20 21:31:09 2023 ++ dmesg -c [17978.613789] null_blk: disk nullb0 created [17978.613814] null_blk: module loaded