linux-kernel - Squashfs on ubi blockdev

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Message-ID: <2d27c68c-4ac8-c0ae-3f95-9b6234a4d31d@geanix.com>
Date:   Wed, 26 May 2021 15:21:00 +0200
From:   Sean Nyekjaer <sean@...nix.com>
To:     dhowells@...hat.com, viro@...iv.linux.org.uk
Cc:     phillip@...ashfs.org.uk, squashfs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Squashfs on ubi blockdev

Hi,

After: 5a2be1288b514 ("vfs: Convert squashfs to use the new mount API")

We see this; when mounting a squashfs from a ubiblockdev:
root@...26-v2:/data/root# mount /dev/ubiblock0_6 /mnt

[   39.884295] /dev/ubiblock0_6: Can't open blockdev

But the filesystem is mounted anyway...

I have tried checking the returned error code get_tree_bdev() -> blkdev_get_by_path() returns -EROFS.

I have also tried to see what happens in squashfs_get_tree() it will be re-run with the ro option set.
Which explains why the filesystem ends up mouted.
[   39.889461] ####Custom debug: squashfs_get_tree -30

[   39.906309] ####Custom debug: squashfs_get_tree 0

Fair enough it's after all a squashfs :)

But could the error message be better? Or just filter out the print when getting a EROFS?

Br,
/Sean