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Mon, 21 Jul 2025 13:37:30 +0000 (GMT) Message-ID: Date: Mon, 21 Jul 2025 19:07:28 +0530 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] null_blk: fix set->driver_data while setting up tagset To: Damien Le Moal , linux-block@vger.kernel.org Cc: hch@lst.de, ming.lei@redhat.com, hare@suse.de, axboe@kernel.dk, johannes.thumshirn@wdc.com, gjoyce@ibm.com References: <20250720113553.913034-1-nilay@linux.ibm.com> <20250720113553.913034-3-nilay@linux.ibm.com> <4b30df72-72e0-484e-99d5-820af02619d9@kernel.org> Content-Language: en-US From: Nilay Shroff In-Reply-To: <4b30df72-72e0-484e-99d5-820af02619d9@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: mzAwUg7uSyTeTF6rpH5zLUKUP8YCDLvz X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzIxMDExNyBTYWx0ZWRfX7OZPu1L+v+cj u/CzYtAOEU94BCjMm88ZRWZyV4EcPNXKcY4T1Rwj03gFBn35wYWFXhJOKvaHJm0VuhpCvjnKnEN Vf1xxe/zJ8r5TmgjY4lrzyMZSF6O5dVRxbJfLSR1jnvU31+cZw72Wb9ahVuWiEizDP+XcraOVlB ppDSdZ/3O0SBv3cMyz4m2D/90BKH/vLGewUVa9howmYeCS6fPJeCdtEMe+Qlpcbq7OtR7M5saLK mQmvhN2OisgAFOtTdyKY58pPMFdGu0Exn304JvM0r27oqA5H/51JCHmORznM5I2Qufqq+iCoQGl tZEB8Nc8ttzwlgyXNsgFTdxuZH2UUZW9uCw0at1QmPkHlv2JAG6dJNNfxKIAQTAH0QgXDizp22L O77F6ASmtXcvwMFzAUK2KBQ1mNiMwFsKB3hvl8a+J7hZkHqrQqK77TXOSd7DK00g+cYBOO+s X-Authority-Analysis: v=2.4 cv=dpnbC0g4 c=1 sm=1 tr=0 ts=687e429f cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Wb1JkmetP80A:10 a=VnNF1IyMAAAA:8 a=NuxngZXgg-Y-D_1eyDsA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: mzAwUg7uSyTeTF6rpH5zLUKUP8YCDLvz X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-07-21_04,2025-07-21_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 impostorscore=0 suspectscore=0 adultscore=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 mlxscore=0 malwarescore=0 mlxlogscore=999 clxscore=1015 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2507210117 On 7/21/25 6:34 PM, Damien Le Moal wrote: > On 2025/07/20 20:35, Nilay Shroff wrote: >> When setting up a null block device, we initialize a tagset that >> includes a driver_data field—typically used by block drivers to >> store a pointer to driver-specific data. In the case of null_blk, >> this should point to the struct nullb instance. >> >> However, due to recent tagset refactoring in the null_blk driver, we >> missed initializing driver_data when creating a shared tagset. As a >> result, software queues (ctx) fail to map correctly to new hardware >> queues (hctx). For example, increasing the number of submit queues >> triggers an nr_hw_queues update, which invokes null_map_queues() to >> remap queues. Since set->driver_data is unset, null_map_queues() >> fails to map any ctx to the new hctxs, leading to hctx->nr_ctx == 0, >> effectively making the hardware queues unusable for I/O. >> >> This patch fixes the issue by ensuring that set->driver_data is properly >> initialized to point to the struct nullb during tagset setup. >> >> Fixes: 72ca28765fc4 ("null_blk: refactor tag_set setup") >> Signed-off-by: Nilay Shroff >> --- >> drivers/block/null_blk/main.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c >> index aa163ae9b2aa..9e1c4ce6fc42 100644 >> --- a/drivers/block/null_blk/main.c >> +++ b/drivers/block/null_blk/main.c >> @@ -1854,13 +1854,14 @@ static int null_init_global_tag_set(void) >> >> static int null_setup_tagset(struct nullb *nullb) >> { >> + nullb->tag_set->driver_data = nullb; >> + > > How can this be correct since the tag_set pointer is initialized below ? > >> if (nullb->dev->shared_tags) { >> nullb->tag_set = &tag_set; > > Shouldn't you add: > > nullb->tag_set->driver_data = nullb; > > here instead ? > >> return null_init_global_tag_set(); >> } Oh yes good catch! I'll fix this in the next patchset. My bad.. :( Thanks, --Nilay