kern/50607: ext2 repeatable kernel panic when creating files

[pooka%iki.fi@localhost]

>Number:         50607
>Category:       kern
>Synopsis:       ext2 repeatable kernel panic when creating files
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jan 02 12:05:00 +0000 2016
>Originator:     Antti Kantee
>Release:        -current sometime after 7.0
>Organization:
>Environment:
>Description:
The ext2 driver dies if it needs to expand the directory when creating a file.  The problem exists only in -current, not NetBSD 7.
>How-To-Repeat:
run tests/fs/vfs/t_vnops::create_many for ext2

https://releng.netbsd.org/b5reports/i386/build/2016.01.01.15.18.39/test.html#fs_vfs_t_vnops_ext2fs_create_many
>Fix: