Re: [PATCH] driver core: Add log when devtmpfs create node failed
From: yangxingui
Date: Thu May 23 2024 - 05:25:21 EST
Hi Greg,
On 2024/5/23 15:25, Greg KH wrote:
On Thu, May 23, 2024 at 09:50:09AM +0800, yangxingui wrote:
Hi, Greg
On 2024/5/22 20:23, Greg KH wrote:
On Wed, May 22, 2024 at 11:43:46AM +0000, Xingui Yang wrote:
Currently, no exception information is output when devtmpfs create node
failed, so add log info for it.
Why? Who is going to do something with this?
We execute the lsscsi command after the disk is connected, we occasionally
find that some disks do not have dev nodes and these disks cannot be used.
Ok, but why do you think that devtmpfs create failed?
I found that lsscsi will traverse the dev node and obtain device major
and min. If no matching dev node is found, it will display "- ".
However, there is no abnormal log output during disk scanning. We analyze
that it may be caused by the failure of devtmpfs create dev node, so the log
is added here.
But is that the case? Why is devtmpfs failing? Shouldn't we fix that
instead?
My subsequent reply touches on these points.
The lscsi command query results and kernel logs as follows:
[root@localhost]# lsscsi
[9:0:4:0] disk ATA ST10000NM0086-2A SN05 -
kernel: [586669.541218] hisi_sas_v3_hw 0000:b4:04.0: phyup: phy0
link_rate=10(sata)
kernel: [586669.541341] sas: phy-9:0 added to port-9:0, phy_mask:0x1
(5000000000000900)
kernel: [586669.541511] sas: DOING DISCOVERY on port 0, pid:2330731
kernel: [586669.541518] hisi_sas_v3_hw 0000:b4:04.0: dev[4:5] found
kernel: [586669.630816] sas: Enter sas_scsi_recover_host busy: 0 failed: 0
kernel: [586669.665960] hisi_sas_v3_hw 0000:b4:04.0: phydown: phy0
phy_state=0xe
kernel: [586669.665964] hisi_sas_v3_hw 0000:b4:04.0: ignore flutter phy0
down
kernel: [586669.863360] hisi_sas_v3_hw 0000:b4:04.0: phyup: phy0
link_rate=10(sata)
kernel: [586670.024482] ata19.00: ATA-10: ST10000NM0086-2AA101, SN05, max
UDMA/133
kernel: [586670.024487] ata19.00: 19532873728 sectors, multi 16: LBA48 NCQ
(depth 32), AA
kernel: [586670.027471] ata19.00: configured for UDMA/133
kernel: [586670.027490] sas: --- Exit sas_scsi_recover_host: busy: 0 failed:
0 tries: 1
kernel: [586670.037541] sas: ata19: end_device-9:0:
model:ST10000NM0086-2AA101 serial: ZA2B3PR2
kernel: [586670.100856] scsi 9:0:4:0: Direct-Access ATA ST10000NM0086-2A
SN05 PQ: 0 ANSI: 5
kernel: [586670.101114] sd 9:0:4:0: [sdk] 19532873728 512-byte logical
blocks: (10.0 TB/9.10 TiB)
kernel: [586670.101116] sd 9:0:4:0: [sdk] 4096-byte physical blocks
kernel: [586670.101125] sd 9:0:4:0: [sdk] Write Protect is off
kernel: [586670.101137] sd 9:0:4:0: [sdk] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
kernel: [586670.101620] sd 9:0:4:0: Attached scsi generic sg10 type 0
kernel: [586670.101714] sas: DONE DISCOVERY on port 0, pid:2330731, result:0
kernel: [586670.101731] sas: sas_form_port: phy0 belongs to port0
already(1)!
kernel: [586670.152512] sd 9:0:4:0: [sdk] Attached SCSI disk
Looks like sdk was found properly, what's the problem?
Yes, this problem occurs occasionally. There is no exception log when
scanning the disk, but the disk cannot be used. It has been confirmed
that it is related to fio testing. When the dev node does not exist, fio
may actively create this file.
Signed-off-by: Xingui Yang <yangxingui@xxxxxxxxxx>
---
drivers/base/core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5f4e03336e68..32a41e0472b2 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3691,7 +3691,10 @@ int device_add(struct device *dev)
if (error)
goto SysEntryError;
- devtmpfs_create_node(dev);
+ error = devtmpfs_create_node(dev);
+ if (error)
+ pr_info("devtmpfs create node for %s failed: %d\n",
+ dev_name(dev), error);
Why is an error message pr_info()?
Do you recommend using pr_err()?
Do not print errors at the information level :)
Ok.
And again, why is this needed? If this needs to be checked, why are you
now checking it but ignoring the error?
What would this help with?
As above, we want to get the error info when the dev node fails to be
created. We currently haven't figured out how to handle this exception well.
But judging from the problems we are currently encountering, some may be
because the corresponding dev node already exists, causing the creation to
fail, but the node information is incorrect and the device cannot be used.
as follows:
[root@localhost]# ll /dev/sdk
-rw-------. 1 root root 5368709120 Jul 8 09:51 /dev/sdk
Looks like the device node is created to me. What is incorrect about
it, the values? What is 'll' an alias for? And are you sure that other
tools aren't getting the device node creation uevent and doing something
with it in userspace? How do you know this is the kernel failing?
Wait, is /dev/sdk really a device node and not a file? Perhaps
something else wrote to it first, before it was created? And that's why
devtmpfs couldn't create it. That sounds like a userspace error,
nothing the kernel can do about it.
Yes, /dev/sdk is a file that may create by fio. and I tried to do the
same and could reproduce the problem, and after adding the log, it shows
that the file already exists.
# ll /dev/sdc
-rw-------. 1 root root 5 Jul 22 00:04 /dev/sdc
[ 366.306045] sas: ata8: end_device-4:1: model:ST2000NM0055-1V4104
serial: ZC21FDJ3
[ 366.306991] scsi 4:0:8:0: Direct-Access ATA ST2000NM0055-1V4
TN05 PQ: 0 ANSI: 5
[ 366.307204] sd 4:0:8:0: [sdc] 3907029168 512-byte logical blocks:
(2.00 TB/1.82 TiB)
[ 366.307212] sd 4:0:8:0: [sdc] Write Protect is off
[ 366.307213] sd 4:0:8:0: [sdc] Mode Sense: 00 3a 00 00
[ 366.307222] sd 4:0:8:0: [sdc] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[ 366.307308] sd 4:0:8:0: Attached scsi generic sg2 type 0
[ 366.307354] sas: DONE DISCOVERY on port 1, pid:8, result:0
[ 366.307364] sas: sas_form_port: phy1 belongs to port1 already(1)!
[ 366.307384] devtmpfs create node for sdc failed: -17
[ 366.307880] sd 4:0:8:0: [sdc] Attached SCSI disk
# lsscsi
[4:0:8:0] disk ATA ST2000NM0055-1V4 TN05 -
If we want to solve this problem, should we delete the existing files
first when creating a dev node? Or just print a prompt indicating that
the dev node creation failed.
Thanks,
Xingui
.