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

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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.

Does this happen only on some specific devices? I see that the error
is mentioning /dev/mmcblk1. Is it the case that it only affects MMC ?
Does this happen when you try to mount a different type of block device
with ext4 on it?

So far I have only seen this with the MMC, but I have not tried others.
Any specific mount options you're using? Is it rw mount? If so, any
chance the device is read only?

Interestingly we are booting with NFS and so not mounting any MMC by default.

Do you have any way of reliably reproducing this?

I see it on every boot and this is causing a warning test to fail. This is a new failure and I have not seen this before. I don't see it on the mainline with the same hardware, only on -next.

Cheers
Jon

--
nvpublic



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