linux-ext4 - e2fsprogs: debugfs: set_inode_field fails to set block[IND]...

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Date:	Mon, 18 Aug 2014 23:32:10 -0500
From:	Jun He <jhe@...wisc.edu>
To:	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: e2fsprogs: debugfs: set_inode_field fails to set block[IND]...

Hi,
I hope this is the right place to report problems of e2fsprogs.

When trying to update block[IND], block[DIND], and block[TIND], it
gives the similar error message:

jhe@...e001:~$ sudo debugfs /dev/loop0 -w -R 'set_inode_field
firstfile block[IND] 2'
debugfs 1.42 (29-Nov-2011)
set_inode_field: invalid field specifier: block[IND]

I looked at the code and found the problem in the following code in
find_field() in debugfs/set_fields.c.

    idx = strchr(arg, '[');
    if (idx) {
        *idx++ = 0;
        delim = idx + strlen(idx) - 1;
        if (!*idx || *delim != ']')
            idx = 0;
        else
            *delim = 0;
    }
    /*
     * Can we parse the number?
     */
    if (idx) {
        array_idx = strtol(idx, &tmp, 0);
        if (*tmp)
            idx = 0;
    }

When the field name is something like "block[4]", this works. It sets
'[' and ']' to 0 and converts the number between them.
When the field name is block[IND], it still replaces '[' and ']' with
0. So arg becomes 'block' and will always fail the following test of
  if (strcmp(ss->name, arg) != 0).

One possible fix is to change the max limit for field 'block', use
number to index IND, DIND, and TIND.
Or, name 'block[IND]', 'block[DIND]', and 'block[TIND]' differently
without the '[' ']'. Such as 'block.IND', 'block.DIND', 'block.TIND'.

If it's just a usage problem, please let me know how to use
set_inode_field to set block[IND].. correctly.

Thanks,
Jun
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