* Re : Query on UFS Lun detection
@ 2021-06-10 13:28 vhiren
2021-06-10 14:51 ` Rob Clark
0 siblings, 1 reply; 2+ messages in thread
From: vhiren @ 2021-06-10 13:28 UTC (permalink / raw)
To: bjorn.andersson, adrian.hunter, robh+dt, ulf.hansson, asutoshd,
stummala, sayalil, rampraka, vbadigan, sboyd, georgi.djakov, mka
Cc: linux-mmc, linux-kernel, linux-arm-msm, devicetree, agross,
linux-mmc-owner, nitirawa
Hi Community,
We are using UFS as a boot device, and we encountered an error,
mentioned below while booting through UFS.
APPS Crash - Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(8,7)
Here in Kernel command line we are passing "root=sda7", this is our
Filesystem partition to be mounted.
While debugging the same we observed the partition which is suppose to
be mounted as Filesystem is not enumerated itself.
The reason behind not enumerating of partition is, the other Lun got
detected first instead of one which is having FS partition.
We are using async probe, hence we know the detection will happen in
async way,
In working case : it looks like below
sd 0:0:0:0: sda1 sda2 sda3 sda4 …..sda8
sd 0:0:0:1: sdb1 sdb2
Here, sd 0:0:0:0 Lun got detected first and enumerated as "sdaN", we
have FS partition as "sda7" and so we don’t see above mentioned error.
In non working case : it looks like below
sd 0:0:0:0: sdb1 sdb2 sdb3 sdb4 …..sdb8
sd 0:0:0:1: sda1 sda2
Here, sd 0:0:0:1 Lun got detected first and enumerated as "sdaN" but we
don’t have FS partition in this Lun. Instead FS partition now became
"sdb7".
Observation here is, which ever Lun gets detected first it will have
"sda" enumeration and so on.
However, sdx’s driver scsi/sd.c uses async probe to improve performance,
meaning sdx disks are created in parallel. Whoever calls
device_add_disk() first becomes sda, the next become sdb….
Is there any way, where we can fix this in the Lun detection part of
code?
Thank You,
Regards,
Hiren Gohel
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Re : Query on UFS Lun detection
2021-06-10 13:28 Re : Query on UFS Lun detection vhiren
@ 2021-06-10 14:51 ` Rob Clark
0 siblings, 0 replies; 2+ messages in thread
From: Rob Clark @ 2021-06-10 14:51 UTC (permalink / raw)
To: vhiren
Cc: Bjorn Andersson, adrian.hunter, Rob Herring, Ulf Hansson,
Asutosh Das, stummala, sayalil, rampraka, vbadigan, Stephen Boyd,
Georgi Djakov, Matthias Kaehlcke, linux-mmc,
Linux Kernel Mailing List, linux-arm-msm,
open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS,
Andy Gross, linux-mmc-owner, nitirawa
On Thu, Jun 10, 2021 at 6:28 AM <vhiren@codeaurora.com> wrote:
>
> Hi Community,
>
> We are using UFS as a boot device, and we encountered an error,
> mentioned below while booting through UFS.
>
>
> APPS Crash - Kernel panic - not syncing: VFS: Unable to mount root fs on
> unknown-block(8,7)
>
> Here in Kernel command line we are passing "root=sda7", this is our
> Filesystem partition to be mounted.
>
> While debugging the same we observed the partition which is suppose to
> be mounted as Filesystem is not enumerated itself.
> The reason behind not enumerating of partition is, the other Lun got
> detected first instead of one which is having FS partition.
Use the UUID or PARTUUID instead, ie:
root=UUID=13846802-672b-4a5d-9f0a-22d13957add3
(but you'd have to check the actual UUID of your partition with a tool
like blkid
BR,
-R
> We are using async probe, hence we know the detection will happen in
> async way,
>
>
> In working case : it looks like below
>
> sd 0:0:0:0: sda1 sda2 sda3 sda4 …..sda8
>
> sd 0:0:0:1: sdb1 sdb2
> Here, sd 0:0:0:0 Lun got detected first and enumerated as "sdaN", we
> have FS partition as "sda7" and so we don’t see above mentioned error.
>
>
> In non working case : it looks like below
>
> sd 0:0:0:0: sdb1 sdb2 sdb3 sdb4 …..sdb8
>
> sd 0:0:0:1: sda1 sda2
> Here, sd 0:0:0:1 Lun got detected first and enumerated as "sdaN" but we
> don’t have FS partition in this Lun. Instead FS partition now became
> "sdb7".
>
>
> Observation here is, which ever Lun gets detected first it will have
> "sda" enumeration and so on.
> However, sdx’s driver scsi/sd.c uses async probe to improve performance,
> meaning sdx disks are created in parallel. Whoever calls
> device_add_disk() first becomes sda, the next become sdb….
>
>
> Is there any way, where we can fix this in the Lun detection part of
> code?
>
> Thank You,
> Regards,
> Hiren Gohel
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-06-10 13:28 Re : Query on UFS Lun detection vhiren
2021-06-10 14:51 ` Rob Clark
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