linux-kernel - Re: [PATCH] jffs2: Fix mounting under new mount API

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Date:   Wed, 13 Nov 2019 14:38:37 -0600
From:   Han Xu <xhnjupt@...il.com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:     David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Richard Weinberger <richard@....at>,
        linux-fsdevel@...r.kernel.org,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] jffs2: Fix mounting under new mount API

Tested the JFFS2 on 5.4 kernel as the instruction said, still got some
errors, any ideas?

Without the patch,

root@...8mmevk:~# cat /proc/mtd
dev:    size   erasesize  name
mtd0: 00400000 00020000 "mtdram test device"
mtd1: 04000000 00020000 "5d120000.spi"
root@...8mmevk:~# mtd_debug info /dev/mtd0
mtd.type = MTD_RAM
mtd.flags = MTD_CAP_RAM
mtd.size = 4194304 (4M)
mtd.erasesize = 131072 (128K)
mtd.writesize = 1
mtd.oobsize = 0
regions = 0

root@...8mmevk:~# flash_erase /dev/mtd0 0 0
Erasing 128 Kibyte @ 3e0000 -- 100 % complete
root@...8mmevk:~# mount -t jffs2 /dev/mtdblock0 test_dir/
mount: /home/root/test_dir: wrong fs type, bad option, bad superblock
on /dev/mtdblock0, missing codepage or helper program, or other error.

With the patch,

root@...8mmevk:~# cat /proc/mtd
dev:    size   erasesize  name
mtd0: 00400000 00020000 "mtdram test device"
mtd1: 04000000 00020000 "5d120000.spi"
root@...8mmevk:~# mtd_debug info /dev/mtd0
mtd.type = MTD_RAM
mtd.flags = MTD_CAP_RAM
mtd.size = 4194304 (4M)
mtd.erasesize = 131072 (128K)
mtd.writesize = 1
mtd.oobsize = 0
regions = 0

root@...8mmevk:~# flash_erase /dev/mtd0 0 0
Erasing 128 Kibyte @ 3e0000 -- 100 % complete
root@...8mmevk:~# mount -t jffs2 /dev/mtdblock0 test_dir/
root@...8mmevk:~# mount
/dev/mtdblock0 on /home/root/test_dir type jffs2 (rw,relatime)

BUT, it's not writable.

root@...8mmevk:~# cp test_file test_dir/
cp: error writing 'test_dir/test_file': Invalid argument

root@...8mmevk:~# dd if=/dev/urandom of=test_dir/test_file bs=1k count=1
dd: error writing 'test_dir/test_file': Invalid argument
1+0 records in
0+0 records out
0 bytes copied, 0.000855156 s, 0.0 kB/s

On Fri, Sep 27, 2019 at 3:38 AM Sergei Shtylyov
<sergei.shtylyov@...entembedded.com> wrote:
>
> Hello!
>
> On 26.09.2019 17:21, David Howells wrote:
>
> > The mounting of jffs2 is broken due to the changes from the new mount API
> > because it specifies a "source" operation, but then doesn't actually
> > process it.  But because it specified it, it doesn't return -ENOPARAM and
>
>     What specified what? Too many "it"'s to figure that out. :-)
>
> > the caller doesn't process it either and the source gets lost.
> >
> > Fix this by simply removing the source parameter from jffs2 and letting the
> > VFS deal with it in the default manner.
> >
> > To test it, enable CONFIG_MTD_MTDRAM and allow the default size and erase
> > block size parameters, then try and mount the /dev/mtdblock<N> file that
> > that creates as jffs2.  No need to initialise it.
>
>     One "that" should be enough. :-)
>
> > Fixes: ec10a24f10c8 ("vfs: Convert jffs2 to use the new mount API")
> > Reported-by: Al Viro <viro@...iv.linux.org.uk>
> > Signed-off-by: David Howells <dhowells@...hat.com>
> > cc: David Woodhouse <dwmw2@...radead.org>
> > cc: Richard Weinberger <richard@....at>
> > cc: linux-mtd@...ts.infradead.org
> [...]
>
> MBR, Sergei
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

-- 
Sincerely,

Han XU

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