Re: [PATCH v3 12/13] ext4: switch to the new mount api

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On 13/01/2022 15:06, Jon Hunter wrote:

On 13/01/2022 12:08, Lukas Czerner wrote:
On Thu, Jan 13, 2022 at 11:29:24AM +0000, Jon Hunter wrote:
Hi Lukas,

On 21/10/2021 12:45, Lukas Czerner wrote:
Add the necessary functions for the fs_context_operations. Convert and
rename ext4_remount() and ext4_fill_super() to ext4_get_tree() and
ext4_reconfigure() respectively and switch the ext4 to use the new api.

One user facing change is the fact that we no longer have access to the
entire string of mount options provided by mount(2) since the mount api
does not store it anywhere. As a result we can't print the options to
the log as we did in the past after the successful mount.

Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>


I have noticed the following error on -next on various ARM64 platforms that
we have ...

  ERR KERN /dev/mmcblk1: Can't open blockdev

I have bisected this, to see where this was introduced and bisect is
pointing to this commit. I have not looked any further so far, but wanted to
see if you had any ideas/suggestions?

Hi,

this error does not come from the ext4, but probably rather from vfs. More
specifically from get_tree_bdev()

         bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
         if (IS_ERR(bdev)) {
                 errorf(fc, "%s: Can't open blockdev", fc->source);
                 return PTR_ERR(bdev);
         }

Yes, obviously this warning has been there for a while but only seen after this change was made.

I have no idea why this fails in your case. Do you know what kind of
error it fails with? Any oher error or warning messages preceding the one you
point out in the logs?

No only this one.

I assume that this happens on mount and the device that you're trying to
mount contains ext4 file system? Ext4 is not the only file system
utilizing the new mount api, can you try the same with xfs on the device?

This is happening on a board in the test farm and so not easy to reformat. Looking some more /dev/mmcblk1 is not a valid device, I only see /dev/mmcblk0 from the bootlogs on this board. Hmmm, OK I will have to take a closer look to see where this is coming from.


OK, I see what is happening. It appears that our test harness always tries to mount a device called /dev/mmcblk1. Prior to this change there was not kernel error generated and looking at the logs I would see ...

mount: /mnt: special device /dev/mmcblk1 does not exist.

Following this change, now a kernel warning is generated and I see ...

[  137.078994] /dev/mmcblk1: Can't open blockdev
mount: /mnt: special device /dev/mmcblk1 does not exist.

So there is a change in behaviour but at the same time the error looks correct. So sorry for the false-positive.

Cheers
Jon



--
nvpublic



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